Regional Pest Management Strategy Cost Benefit Analysis

APPENDIX E: REGIONAL PEST MANAGEMENT STRATEGY COST BENEFIT ANALYSIS – TENAX CONSULTING LIMITED FOR THE BAY OF PLENTY REGIONAL COUNCIL Pest impact assessment and cost-beneﬁt analysis for the proposed Bay of Plenty Regional Pest Management Strategy

Jon J. Sullivan1, Melissa Hutchison2

1 Bio-Protection Research Centre PO Box 84, Lincoln University Lincoln 7647, New Zealand [email protected]

2 Tenax Consulting Ltd 16 Samuel Street, Christchurch [email protected]

May 2010 ©2010, (version 31 May 2010) Bio-Protection Research Centre, Lincoln University. Report prepared by the Bio-Protection Research Centre for Environment Bay of Plenty, May 2010. Any publication, reproduction, or adaptation of this report must be authorised by Environment Bay of Plenty. Executive Summary

This report assesses the impacts of plant and animal pests listed in the proposed Bay of Plenty Regional Pest Management Strategy (RPMS) and evaluates the costs and benefits of the proposed regional actions. This is done to meet the requirements of Section 72(1) of the New Zealand Biosecurity Act 1993. We use data from Environment Bay of Plenty sta↵ and published information to summarise the known impacts of 44 pest plants and 23 pest animals on production values as well as natural, social, and cultural values. We perform cost-benefit analyses (CBAs) on each species using a modified version of the Harris Model. The Harris Model was developed in 2000 by economist Simon Harris specifically for RPMS assessments and it has been commonly used. Our modifications to the Harris Model are designed to make it both more diverse and less precise in its data requirements. These make it more capable of incorporating the diverse range of pests and impacts that face the Bay of Plenty region, while retaining its robust economic foundations. In addition to our standard assessments of impacts, costs, and benefits for the many pests, we also provide more detailed assessments for pests of special concern. The pests of special interest to the Environment Bay of Plenty regional council were wilding pines, gorse in lake catchments where it contributes to nitrogen leaching into lakes, pest fish (gambusia and the coarse fish brown catfish, koi carp, perch, rudd, and tench), and boundary control of the three widespread weeds, gorse, blackberry, and ragwort. Contents

1 Introduction 1 1.1 Introduction ...... 1 1.2 Methodology ...... 1 1.3 Assumptions ...... 3 1.4 Determining beneﬁciaries and exacerbators ...... 3

2 Pest plants (weeds) 5 2.1 Pest plants ...... 5 2.1.1 African feather grass (Pennisetum macrourum) ...... 9 2.1.2 Alligator weed (Alternanthera philoxeroides) ...... 14 2.1.3 Apple of Sodom (Solanum linnaeanum) ...... 19 2.1.4 Asiatic knotweed (Reynoutria japonica) ...... 24 2.1.5 Banana passionfruit (Passiflora tripartita var.mollissima, P. tarmini- ana, P. caerulea) ...... 29 2.1.6 Blackberry (Rubus fruticosus agg.) ...... 34 2.1.7 Boneseed (Chrysanthemoides monilifera) ...... 39 2.1.8 Cathedral bells (Cobaea scandens) ...... 44 2.1.9 Chilean rhubarb (Gunnera tinctoria) ...... 49 2.1.10 Climbing spindleberry (Celastrus orbiculatus) ...... 54 2.1.11 Coast tea tree (Leptospermum laevigatum) ...... 59 2.1.12 Darwin’s barberry (Berberis darwinii) ...... 64 2.1.13 Egeria densa (Egeria densa) ...... 69 2.1.14 Elodea canadensis (Elodea canadensis) ...... 71 2.1.15 Gorse (Ulex europaeus) ...... 77 2.1.16 Green goddess lily (Zantedeschia aethiopica “Green goddess”) .... 82 2.1.17 Hornwort (Ceratophyllum demersum) ...... 87 2.1.18 Horse nettle (Solanum carolinense) ...... 91 2.1.19 Italian buckthorn (Rhamnus alaternus) ...... 96 2.1.20 Kudzu vine (Pueraria montana var.lobata) ...... 101 2.1.21 Lagarosiphon (Lagarosiphon major) ...... 106 2.1.22 Lantana (Lantana camara var.aculeata) ...... 110 2.1.23 Marshwort (Nymphoides geminata) ...... 115 2.1.24 Nassella tussock (Nassella trichotoma) ...... 117 2.1.25 Noogoora bur (Xanthium strumarium) ...... 122 2.1.26 Old man’s beard (Clematis vitalba) ...... 127 2.1.27 Pampas (Cortaderia selloana, C. jubata and cultivars) ...... 132 2.1.28 Privet (Ligustrum lucidum, L. sinense) ...... 137 2.1.29 Ragwort (Senecio jacobaea) ...... 142 2.1.30 Royal fern (Osmunda regalis) ...... 147 2.1.31 Saltwater paspalum (Paspalum vaginatum) ...... 152 2.1.32 Senegal tea (Gymnocoronis spilanthoides) ...... 157 2.1.33 Spartina (Spartina anglica, S. alterniflora, S...... 159 2.1.34 Strawberry dogwood (Dendrobenthamia capitata) ...... 164 2.1.35 Variegated thistle (Silybum marianum) ...... 169 2.1.36 Water poppy (Hydrocleys nymphoides) ...... 174 2.1.37 White-edged nightshade (Solanum marginatum) ...... 176 2.1.38 Wild ginger (yellow and kahili) (Hedychium gardnerianum, H. flavescens)181 2.1.39 Wild kiwifruit (Actinidia spp.) ...... 186 2.1.40 Wild purple loosestrife (Lythrum salicaria) ...... 191 2.1.41 Woolly nightshade (Solanum mauritianum) ...... 193 2.1.42 Yellow flag iris (Iris pseudacorus) ...... 198 2.1.43 Pest plant beneficiaries and exacerbators ...... 203

3 Pest animals 206 3.1 Pest animals ...... 206 3.1.1 Argentine ant (Linepithema humile) ...... 208 3.1.2 Darwin ant (Doleromyrma darwiniana) ...... 213 3.1.3 Eastern rosella (Platycerus eximius) ...... 218 3.1.4 Feral cat (Felis catus) ...... 223 3.1.5 Feral goat (Capra hircus) ...... 228 3.1.6 Ferret (Mustela furo) ...... 233 3.1.7 Hedgehog (Erinaceus europaeus) ...... 238 3.1.8 Magpie (Gymnorhina hypoleuca) ...... 243 3.1.9 Mouse (Mus musculus) ...... 248 3.1.10 Possum (Trichosurus vulpecula) ...... 253 3.1.11 Rabbit (Oryctolagus cuniculus) ...... 259 3.1.12 Rat (ship and Norway) (Rattus rattus, R. norvegicus) ...... 264 3.1.13 Rook (Corvus frugilegus) ...... 269 3.1.14 Stoat (Mustela ermina) ...... 274 3.1.15 Wallaby (Macropus eugenii) ...... 279 3.1.16 Wasp (Vespula spp., Polistes spp.) ...... 283 3.1.17 Weasel (Mustela nivalis) ...... 288 3.1.18 Pest animal beneﬁciaries and exacerbators ...... 293

4 Pests of special concern 296 4.1 Wilding pines ...... 296 4.1.1 Introduction ...... 296 4.1.2 Wilding pine species ...... 297 4.1.3 Carbon costs of tree weed control ...... 298 4.1.4 Wilding pine impacts and CBA ...... 298 4.1.5 Lodgepole pine (Pinus contorta) ...... 301 4.1.6 Wilding pine conclusions & recommendations ...... 309 4.2 Lake gorse ...... 311 4.2.1 Introduction ...... 311 4.2.2 Gorse, a brief natural history ...... 312 4.2.3 Lake gorse impacts and CBA ...... 312 4.2.4 Lake gorse conclusions & recommendations ...... 319 4.3 Pest fish ...... 321 4.3.1 Introduction ...... 321 4.3.2 Species ...... 321 4.3.3 Pest fish Impacts and CBA ...... 322 4.3.4 Brown bullhead catfish, Ameiurus nebulosus ...... 323 4.3.5 Catfish (Ameiurus nebulosus) ...... 323 4.3.6 Koi carp, Cyprinus carpio ...... 326 4.3.7 Koi carp (Cyprinus carpio) ...... 327 4.3.8 Perch, Perca fluviatilis ...... 329 4.3.9 Perch (Perca fluviatilis) ...... 330 4.3.10 Rudd, Scardinius erythrophthalmus ...... 332 4.3.11 Rudd (Scardinius erythropthalmus) ...... 333 4.3.12 Tench, Tinca tinca ...... 335 4.3.13 Tench (Tinca tinca) ...... 336 4.3.14 Gambusia, Gambusia anis ...... 338 4.3.15 Gambusia (Gambusia anis) ...... 339 4.3.16 Costs and benefits of a ban on coarse fishing ...... 340 4.3.17 Coarse fish conclusions & recommendations ...... 341 4.4 Boundary weeds ...... 342 4.4.1 Introduction ...... 342 4.4.2 Species natural history ...... 342 4.4.3 Boundary weed impacts and CBA ...... 343 4.4.4 Boundary weeds conclusions & recommendations ...... 345

Appendices 346

A Data assumptions and limitations 347 A.1 Habitat types occupied by pest species ...... 347 A.2 Economic value of di↵erent habitat types ...... 349 A.3 Current habitats infested ...... 350 A.3.1 Current area infested (ha) ...... 350 A.4 Potential habitats infested ...... 350 A.5 Potential area infested (ha) ...... 350 A.6 Impact categories ...... 350 A.7 Dispersal mode (pest plants only) ...... 351 A.8 Dispersal rate (pest plants only) ...... 351 A.9 Life form (pest plants only) ...... 351 A.10 Environment Bay of Plenty annual cost of pest management ...... 352 A.11 E↵ectiveness of control (pest plants only) ...... 352 A.12 Benefits of pest ...... 353 A.13 Value of benefits of pest ...... 353 A.14 Defined areas for some pests ...... 353

B The modiﬁed Harris Model for cost-beneﬁt analysis of regional pest control 354 B.1 Introduction ...... 354 B.2 Interpreting CBA results ...... 354 B.3 Changes to the Harris Model ...... 355 B.4 Estimating potential area ...... 357 B.5 Estimating spread time ...... 357 B.6 Estimating impacts ...... 360 B.7 Estimating the e↵ectiveness of control ...... 361 B.8 Increasing pest impacts over time ...... 361 Chapter 1

Introduction

1.1 Introduction

Section 72 of the Biosecurity Act (1993) (hereafter the Act) requires a detailed assessment be made of the costs and benefits of proposed pests and their proposed control strategies, including an assurance that the net benefits of regional intervention outweigh pest control by individuals. Section 76 of the Act requires that proposed Regional Pest Management Strategies (RPMS) must present the costs and benefits of each pest (76(k)) and the cost- benefit analysis of pests under di↵erent control strategies (76(l)). This report meets the requirements of the Act by providing an assessment of the detrimental e↵ects and any known beneficial e↵ects of listed pests, and providing a cost-benefit analysis for each comparing “no control” to one or more of the “Control Pest”, “Exclusion Pest” and “Advisory Pest” RPMS scenarios. As in other RPMS CBA reports, we ask whether the costs and benefits justify the inclusion of each pest in the RPMS in the category proposed. In other words, are the benefits of proposed regional investment in controlling a pest likely to be greater than the costs. We do not attempt to estimate the optimal proportion of all available regional biosecurity funds that should be directed at each pest for the greatest overall benefit. Doing so would require a more nuanced and political discussion than is within the scope of a CBA, part of which is captured in the public submission process for the proposed RPMS.

1.2 Methodology

For each species, we use available information to assess the impacts and perform a cost- beneﬁt analysis (CBA) for no RPMS control compared with one or more relevant categories proposed for the next Bay of Plenty RPMS (Agency Pest, Exclusion Pest, Control Pest, Advisory Pest, and Boundary Control Pest). The CBA method we use is a modiﬁcation of the Harris Model created by Simon Harris of Harris Consulting, Christchurch, for the Biosecurity Managers Group. The Harris Model has been used for several RPMS CBAs, including the previous Bay of Plenty CBA (Severinsen 2003). Our impact assessments follow the general structure of pest assessments in other recent RPMS (e.g., Severinsen 2003; Auckland Regional Council 2006). Detailed and quanti-

1 tative descriptions of the impacts of each pest are beyond the scope of this document, and are unnecessary. Instead, we summarise the most important impacts and assign a ”low”, ”moderate”, or ”high” impact value for each impact category (e.g., human health, soil resources, production). These are typically adequate to assess whether a pest has adequately high impacts to justify its inclusion in the proposed RPMS. For each species in this report we broadly assess their impacts on the following aspects of the Bay of Plenty region. • Species diversity: impact on native species. • Threatened species: impact on threatened species i.e. plants listed in de Lange et al. (2009) and animals listed in Hitchmough et al. (2005). • Soil resources: causes soil loss or erosion, alters soils fertility or moisture levels. • Water quality: increases siltation or sedimentation, reduces oxygenation of water. • Production: impact on agricultural production or forestry. • International trade: impact on international exports. • Recreation: prevents or restricts recreational use. • M¯aoriculture: impact on M¯aoricultural activities (e.g., seafood harvesting, food gathering) or M¯aori cultural sites (e.g., pa, marae, urupa (burial grounds)). These impacts are detrimental in nature. We assess any beneficial impacts and incorporate them into the CBA. The cost-benefit analyses in Severinsen (2003) were well constructed and appear economically robust. However, they often required unrealistically precise values for ecological parameters, ignored the costs of non-production impacts, and provided no estimates of the uncertainty around the final estimates of costs and benefits. Our modified methods attempt to improve on these areas. We allow for the inclusion of a range of ecological values where a precise number is unknown (e.g., potential rate of spread) and we allow for the inclusion of (typically small) per hectare non-production costs. We employ a commonly used economic method to assess the sensitivity of our conclusions to the values of our various parameters, by increasing and decreasing them by 10% and 70% and seeing which alters the conclusions of a CBA. This is a way of identifying which parameters need to be most accurately quantified and can in this way be used to assess the robustness of CBA conclusions. We are ecologists, not economists, and so have not changed the underlying economic equations in the Harris model. Instead, we have made our modifications around these equations. For example, allowing for a range of values rather than a single value is the same as running the Harris model twice with the high and low value of a range. Adding costs of non-production impacts simply requires re-running the Harris Model with the addition of per hectare impacts on things like soil quality and biodiversity (such values are notoriously dicult to assign dollar values but excluding them altogether is at least as unrealistic—we have typically assigned these small, non-zero numbers relative to production impacts to assess their possible importance). When we do this, we are sure to also include the CBA results when only production impacts are included. Our most fundamental modification is the use of a mathematically di↵erent “S-shaped” growth curve to the Harris Model when we predict the expansion of pests. We use a logistic

2 growth curve widely used in ecology for weed modelling. In comparison to the Harris Model growth curve, our logistic growth curve includes a shorter “establishment-phase” (the time before a species begins to rapidly spread), a longer spread phase, and a shorter plateau. Our model has each phase occupying a third of the invasion. Long lag-phases are well documented in invasion biology, especially in the period between the introduction of a species (e.g., for forestry) and its first wild establishment (e.g., Mulvaney 2001), but most of the species listed in the RPMS are expected to be beyond this early phase. Our shorter establishment phase is more likely to reflect the behaviour of an already identified weed. Usefully, the logistic growth curve also simplifies the mathematics allowing for an easier separation to the population growth time and the time period over which the costs are calculated. This is very helpful in that it makes it easy to not run out the model for all the time required for a pest to reach its full extent. It is also flexible enough to add a lag-phase for other pests if it is considered likely. We have also been careful throughout to identify all of our data sources which will add transparency to this process and make it simple to incorporate new information into revised cost and benefit estimates as it becomes available. Our full methods are described in Appendix B.

1.3 Assumptions

We follow the assumptions of the Harris Model. This includes the assumption that the impacts of pests (economic and environmental costs) scale linearly with area of infestation. Twice as much area of weeds means twice as much impact on the region. In all cases we use an annual discount rate of 8% throughout to convert future costs and beneﬁts into Net Present Value, in keeping with other RPMS cost-beneﬁt analyses (e.g., Severinsen 2003; Auckland Regional Council 2006). This is the foundation of the CBA approach: current investments made to avoid future pest impacts are considered uneconomical if the same money invested now would be worth more than the impact costs when those impacts occur.

1.4 Determining beneﬁciaries and exacerbators

Section 72(1)ba of the Biosecurity Act states that “where funding proposals require persons to meet directly the costs of im- plementing the strategy - 1. the benefits that will accrue to those persons as a group will outweigh the costs; or 2. those persons contribute to the creation, continuance, or exacerbation of the problems proposed to be addressed by the strategy” Beneficiaries and exacerbators were identified for pests only in the Control category (including those with control in defined areas), as the costs of the strategies for Exclusion and Advisory pests will be met by Environment BOP (i.e. the regional community) and will not be imposed on individual landowners.

3 Beneficiaries and exacerbators were determined for the di↵erent habitat (land use) type categories. For the purposes of this analysis the Native, Urban, Coastal, Freshwater and Estuarine habitat types were combined into one Regional community category. Beneficiaries and exacerbators were classed as minor or major, based on information in Severinsen (2003) and whether the habitats were defined as primary or secondary habitats.

4 Chapter 2

Pest plants (weeds)

2.1 Pest plants

For each pest plant we present a brief description of its relevant biology, summarise its impacts of assorted values in the Bay of Plenty, and present the results of a cost-benefit analysis of available data for the species assigned to each of the Exclusion, Control, and Advisory categories. See the Appendices for information on the methods, assumptions, and data limitations. The results of the weed CBAs are summarised in Table 2.1.TheseshowTRUE when a scenario is cost beneficial and FALSE when it is not. The values in bold are those scenarios in the propsed RPMS. In almost all cases, the proposed scenarios are cost e↵ective. When a proposed RPMS category shows FALSE* in Table 2.1, such as happens with boneseed, this means that the CBA results are uncertain about whether this level of expenditure is likely to be cost beneficial. This typically reflects inadequate knowledge of the economic value of weed impacts, especially for impacts outside of agriculture which are inherently harder to quantify. We recommend a precautionary approach to these weeds, meaning that they should be managed in their proposed categories if adequate funding is available. When dealing with expanding weed populations, early action is the far and away the most cost e↵ective approach even when there is inadequate knowledge of impacts (Harris & Timmins 2009). The weeds with blank lines in Table 2.1 are weeds that are currently absent from the region (the Exclusion weeds) or absent from their defined areas within the region (Control (defined lakes)). In these cases, it is dicult to simulate the results of placing these weeds in other RPMS categories. The management aim is not the reducing populations but preventing establishment. It is dicult to balance costs and benefits in these situations because it is not known how soon these weeds will likely expand into the region (or defined area) without regional surveillance and control activities. What we do for each of these species is quantify the impacts of each species if it invaded now and spread over the next 50 years without regional control. This can be seen as the worst case scenario for these weeds and is the justification for investing in excluding these species if these costs are higher than the projected exclusion costs. For all Exclusion weeds, the projected impacts should they invade now are larger (usually by many tens of thousands of dollars) than the proposed costs of keep them from the

5 region (and eradicating them should they be detected by surveillance). These species are marshwort, Senegal tea, water poppy, and wild purple loosestrife. The CBA results are less clear for the aquatic lake weeds proposed as Control (defined lakes). These are all species that are well recognised as bad weeds both nationally and internationally. They are present in some lakes in the region already and eradication from these lakes is e↵ectively impossible in most cases. The management aim for the foreseeable future is therefore to prevent their establishment in lakes free of these weeds. For Egeria densa and Lagarosiphon, the proposed costs are less than the projected impacts. However, the projected impacts are worth less than the proposed control for hornwort. This is a well recognised and clearly damaging lake weed and we are skeptical that the proposed costs would not be justified if the economic values of hornwort impacts on tourism, recreation, and biodiversity were more carefully quantified. Other than hornwort, the one species that does not emerge as being cost-beneficial in the CBA results is spartina. This is an aggressive plant in estuaries that has been planted for erosion control but grows in thick monocultures excluding other species. The CBA is not cost beneficial because the impacts are not easy to quantify (it only has impacts on values in estuaries, which are hard to put dollar values on). It is also because spartina is an estuary specialist and so will never occur in a large area of the region (because of this, any multiplication of dollars per hectare ×area will produce a low number). If the Council values the ecological integrity of the region’s estuaries and the ecosystem services they provide at more than $50,600 in total (in current dollars, for the full 50 years, not per year) over the next 50 years, this will still satisfy section 72(1a) of the Act for spartina to be managed as an Exclusion pest, as has been proposed.

6 Table 2.1: Summary of weed CBA results showing which of the three RPMS control scenarios are regarded as economically beneﬁcial regional investments over 50 years. As- terisked values are instances where using the average impact and spread values have costs somewhat greater than beneﬁts whereas using the maximum values of impacts and spread have costs less than impacts. Blanks are weeds not present in the region (see summary of these results in the text above).

Weed 2010 RPMS category Advisory Control Exclusion African feather grass Control TRUE TRUE TRUE Alligator weed Exclusion TRUE TRUE TRUE Apple of Sodom Control TRUE TRUE FALSE Asiatic knotweed Control TRUE TRUE FALSE Banana passionfruit Advisory TRUE FALSE* FALSE Blackberry Advisory TRUE TRUE TRUE Boneseed Control TRUE FALSE* FALSE Cathedral bells Advisory TRUE FALSE* FALSE Chilean rhubarb Control TRUE TRUE FALSE Climbing spindleberry Control TRUE TRUE FALSE Coast tea tree Control TRUE TRUE TRUE Darwin’s barberry Control TRUE TRUE FALSE Egeria densa Control (defined lakes) Elodea canadensis Advisory TRUE FALSE* FALSE Gorse Advisory TRUE TRUE TRUE Green goddess lily Control TRUE TRUE FALSE Hornwort Control (defined lakes) Horse nettle Exclusion TRUE TRUE TRUE Italian buckthorn Control TRUE TRUE TRUE Kudzu vine Exclusion TRUE TRUE TRUE Lagarosiphon Control (defined lakes) Lantana Control TRUE TRUE FALSE Lodgepole pine Control TRUE TRUE TRUE Marshwort Exclusion Nassella tussock Exclusion TRUE TRUE TRUE Noogoora bur Exclusion TRUE TRUE TRUE Old man’s beard Control TRUE TRUE FALSE Pampas Advisory TRUE TRUE FALSE Privet Advisory TRUE FALSE* FALSE Ragwort Advisory TRUE TRUE TRUE Royal fern Control TRUE TRUE FALSE Saltwater paspalum Advisory TRUE FALSE FALSE Senegal tea Exclusion Spartina Exclusion FALSE* FALSE FALSE Strawberry dogwood Advisory TRUE TRUE FALSE Variegated thistle Control TRUE TRUE TRUE Water poppy Exclusion White-edged nightshade Exclusion TRUE TRUE TRUE Wild ginger (yellow and kahili) Control TRUE TRUE FALSE Wild kiwifruit Control TRUE TRUE FALSE Wild purple loosestrife Exclusion continued

7 Table 2.1: Summary of weed CBA results showing which of the three RPMS control scenarios are regarded as economically beneﬁcial regional investments over 50 years. As- terisked values are instances where using the average impact and spread values have costs somewhat greater than beneﬁts whereas using the maximum values of impacts and spread have costs less than impacts. Blanks are weeds not present in the region (see summary of these results in the text above).

Weed 2010 RPMS category Advisory Control Exclusion Woolly nightshade Control (deﬁned areas) TRUE TRUE FALSE Yellow ﬂag iris Control TRUE TRUE FALSE

8 2.1.1 African feather grass (Pennisetum macrourum)

Proposed RPMS Category: Control Overall impact: Major

Table 2.2: Relevant biology

Attribute Description Form A robust rhizomatous perennial grass up to 1.5 m tall with overhanging ﬂower spikes which resembles pampas grass. The inﬂorescence is 10-25 cm long, 2 cm in diameter and reddish purple. Habitat Prefers damp situations such as swamps or stream and lake margins, but grows in a range of soil types including sand. Regional distribution Light infestations in the Rotorua area. Isolated in other parts of the region. Competitive ability Forms dense clumps that exclude other vegetation. Reproductive ability Seed viability is high but seedling establishment is poor. Dispersal methods Seed dispersed by wind, water, and animals. Also spreads from far creeping rhizomes and may spread through cultivation with contaminated machinery. Resistance to control Readily controlled by appropriate herbicides.

Table 2.3: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity L M Forms dense clumps and out-competes na- 1, 2 tive pioneer species in many vulnerable habitats. Also invades established plant communities. Can harbour rats, mice and possums. Threatened species L M 1, 2 Soil resources - L Causes accretion of sand and changes in 1 habitat, leading to erosion or ﬂooding, loss of dunelakes and wetlands. Water quality - L See Soil Resources. 1 Production - H Unpalatable to livestock. Fire hazard. 1, 2, 3 International trade - M Can contaminate wool. Crop contami- 1, 4 nant, prohibited seed (nil tolerance) in imports into Australia. Human health - - 5 Recreation - M Obstructs access to lakes, beaches. 1 M¯aoriculture - M Obstructs access to cultural sites (e.g. 5 waahi tapu, urupa). Source: 1: Craw (2000), 2: Environment Bay of Plenty (2005a), 3: Environment Bay of Plenty (2004a), 4: Anon. (2009k), 5: Severinsen (2003)

9 African feather grass CBA results

The following are results for cost-beneﬁt analyses for four scenarios, no regional RPMS control, RPMS control as an Exclusion Pest, RPMS control as a Control Pest, and RPMS control as an Advisory Pest. For the purposes of the CBA calculations, the pest is assumed to continue expanding with no regional RPMS control, its spread is assumed to be near-arrested under Advisory Control but not reduced, and it is assumed to be successfully reduced to the expected smaller extent when listed as a Control Pest, more so as an Exclusion pest.

Table 2.4: African feather grass CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 13,929,147 0 0 -13,929,147 (5,613,070–54,976,806) (-5,613,070 – -54,976,806) Exclusion Pest 1 13,929,146 6,746,639 7,182,507 (0–1) (5,613,070–54,976,805) (-1,133,569 – 48,230,166) Control Pest 2 13,929,145 264,243 13,664,902 (0–3) (5,613,070–54,976,803) (5,348,827 – 54,712,560) Advisory Pest 1 13,929,146 13,212 13,915,934 (0–1) (5,613,070–54,976,805) (5,599,858 – 54,963,593)

Table 2.5: African feather grass CBA base assumptions.

Base assumptions Values Current area infested (ha) 1 Total area potentially infested (ha) 143,868 (48,473–239,262) Years from naturalisation to total area 75 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 0.1 (0.1–0.1) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.6: African feather grass RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 0.1 (0–0.2)

Table 2.7: African feather grass RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 1 (0–2)

Table 2.8: African feather grass RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5

10 Final area infested (ha) 1 (1–2)

Table 2.9: African feather grass estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 1,000,000 20,000 1,000

African feather grass conclusions

In the absence of regional control, the projected total regional damage in net present value is -$13,929,147 over the next 50 years (the minimum projected impact is -$5,613,070). Managing African feather grass as an Exclusion pest has a projected net benefit to the region of $7,182,507. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing African feather grass as a Control pest has a projected net benefit to the region of $13,664,902. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing African feather grass as an Advisory pest has a projected net benefit to the region of $13,915,934. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for African feather grass, Control, therefore meets the requirements of Section 72(1a) of the Act.

11 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 1 0.4 Potential extent (ha): 143,868

(48,473−−239,262) Proportion extent of maximum 0.2 Time to potential (yr): 75

Current prop. of potential: <0.01 0.0

0 20 40 60

Years from present

Figure 2.1: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

12 ● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory control● ●

●

1.0 ● 1.0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 1.0 ● 200000 ●

0.8 ● 0.8 0.8

● 150000 0.6 ● 0.6 0.6

● 100000 ● 0.4 0.4 0.4 ● ● ● ● ● ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● ● ● ● ● 50000 ● ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 13

1.0 ● 1.0 ● 1.0 ●

● 200000 Discount rate: 0.08 ● ● ● ● ● Total multiplier: 54103.51 0.8 0.8 ● 0.8 ●

● (32533−−160576) 150000 ● ● ●

0.6 0.6 ● 0.6

● ● ●

● 100000 ● ● 0.4 0.4 ● 0.4 ● ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● 50000 ● ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.2: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.2 Alligator weed (Alternanthera philoxeroides)

Proposed RPMS Category: Exclusion Overall impact: Major

Table 2.10: Relevant biology

Attribute Description Form A ﬂoating aquatic, but sometimes terrestrial, perennial herb. Stems are green-brown, hollow and rooting at nodes. Leaves are obovate to narrow-elliptical. Habitat Still water to 1.5 m deep, or ﬂowing fresh water. Tolerates up to 30% sea water. Will grow on moist banks, swampy places, damp pasture and dropping land. Regional distribution Isolated infestations at Pikowai, Edgecumbe, Te Maunga and Katikati. Competitive ability Floating mats shade out other plants. Biomass doubles in 50 days. Will out-compete pasture species. Reproductive ability No viable seeds are produced. Dispersal methods Fragments dispersed by cultivation machinery, as weeds or contaminants of aquatic plant trade. Resistance to control E↵ective control is dicult, even in small waterways, swampy pastures and cropping land. Use of herbicide in and beside waterways makes control dicult.

Table 2.11: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity - H Forms dense mats over water and around 1 margins of waterways. Roots down to 2 m deep, replaces most other herbaceous species on water and dry land. Rotting vegetation degrades habitat for aquatic fauna and flora. Threatened species - H 1 Soil resources - - 1 Water quality - M Causes silt accumulation and flooding. 1 Rotting vegetation degrades water quality. Production L M Can spread from waterways onto cropping 1, 2, 3 land, out-competes other species. Causes photosensitivity in stock. International trade - - 4 Human health - - 4 Recreation - H Obstructs access to waterways for fishing, 4 swimming, kayaking etc. M¯aoriculture - L See Recreation. 4 Source: 1: Craw (2000), 2: Roy et al. (2004), 3: Environment Bay of Plenty (2004a), 4: Severinsen (2003)

14 Alligator weed CBA results

Table 2.12: Alligator weed CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 1,283,136 0 0 -1,283,136 (310,129–4,659,531) (-310,129 – -4,659,531) Exclusion Pest 2,496 1,280,640 134,933 1,145,707 (542–4,112) (309,587–4,655,419) (174,654 – 4,520,486) Control Pest 7,637 1,275,499 5,285 1,270,214 (1,445–14,489) (308,684–4,645,042) (303,399 – 4,639,757) Advisory Pest 4,603 1,278,533 13,212 1,265,321 (674–10,506) (309,455–4,649,025) (296,243 – 4,635,813)

Table 2.13: Alligator weed CBA base assumptions.

Base assumptions Values Current area infested (ha) 10 Total area potentially infested (ha) 12,979 (4,830–21,127) Years from naturalisation to total area 75 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 58.61 (11.72–105.5) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.14: Alligator weed RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 1.2 (0–2.5)

Table 2.15: Alligator weed RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 12 (15–10)

Table 2.16: Alligator weed RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 25 (35–15)

15 Table 2.17: Alligator weed estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 20,000 400 1,000

Alligator weed conclusions

In the absence of regional control, the projected total regional damage in net present value is -$1,283,136 over the next 50 years (the minimum projected impact is -$310,129). Managing Alligator weed as an Exclusion pest has a projected net benefit to the region of $1,145,707. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Alligator weed as a Control pest has a projected net benefit to the region of $1,270,214. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Alligator weed as an Advisory pest has a projected net benefit to the region of $1,265,321. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Alligator weed, Exclusion, therefore meets the requirements of Section 72(1a) of the Act.

16 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 10 0.4 Potential extent (ha): 12,979

(4,830−−21,127) Proportion extent of maximum 0.2 Time to potential (yr): 75

Current prop. of potential: 0.001 0.0

0 20 40 60

Years from present

Figure 2.3: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

17 Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory control

2000 1.0 ● 1.5 3.5

● 3.0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.8 ● ● ● ● ● ● ● ● ● 1500 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 2.5 ● ● ● ● ● ● 1.0 ● ● ● ● 0.6 ● 2.0 ● 1000 ●

●

● 1.5 0.4 ● ● ● ● ● ● ● ● ● ● ● 0.5 ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● 1.0 ● 500 ● ● ● ● ● 0.2 ● ● ● ● 0.5 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

● 0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5 ● Years from present Years from present Years from present Years from present

●

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control ● 18 2000 1.0 ● 1.0 ● 1.0 ●

Discount rate: 0.08 ●

Total multiplier: 688.03 0.8 0.8 ● 0.8 ● 1500 ●

(497−−1419) ●

● ● 0.6 0.6 ● 0.6 ● 1000 ● ● ● ● ● ● 0.4 0.4 ● 0.4 ● ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● 500 ● ● ● ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.4: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.3 Apple of Sodom (Solanum linnaeanum)

Proposed RPMS Category: Control Overall impact: Moderate

Table 2.18: Relevant biology

Attribute Description Form Strongly spiny, woody, perennial shrub up to 1 m tall. Green and white berries ripen to yellow. Habitat Frost-free coastal areas, poor pasture and scrub margins. Regional distribution Scattered in coastal areas. Competitive ability Can out-compete some species in coastal areas, but does not usually form pure stands. Reproductive ability Produces viable seed. Dispersal methods Seeds dispersed by birds. Resistance to control Can be controlled with picloram.

Table 2.19: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity L L Forms dense thickets in coastal areas, ex- 1 cluding low-growing native species. Threatened species - L 1 Soil resources - - 2 Water quality - - 2 Production L M Leaves and unripe fruit are toxic to stock. 1, 3, 4 International trade - - 2 Human health - M Leaves and unripe fruit are poisonous to 1, 3 humans. Recreation - M Spiny shrub restricts access to beaches. 1, 3 M¯aoriculture - M Obstructs access to cultural sites (e.g. 1, 3 waahi tapu, urupa). Source: 1: Craw (2000), 2: Severinsen (2003), 3: Roy et al. (2004), 4: Environment Bay of Plenty (2004a)

19 Apple of Sodom CBA results

Table 2.20: Apple of Sodom CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 1,125,267 0 0 -1,125,267 (257,779–3,043,407) (-257,779 – -3,043,407) Exclusion Pest 15,317 1,109,950 6,746,639 -5,636,689 (3,136–25,392) (254,643–3,018,015) (-6,491,996 – -3,728,624) Control Pest 42,820 1,082,447 66,061 1,016,386 (8,274–75,724) (249,505–2,967,683) (183,444 – 2,901,622) Advisory Pest 28,247 1,097,020 13,212 1,083,808 (3,903–64,873) (253,876–2,978,534) (240,664 – 2,965,322)

Table 2.21: Apple of Sodom CBA base assumptions.

Base assumptions Values Current area infested (ha) 78 Total area potentially infested (ha) 55,049 (19,374–90,723) Years from naturalisation to total area 125 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 46.11 (8.7–83.52) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.22: Apple of Sodom RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 9.8 (0–19.5)

Table 2.23: Apple of Sodom RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 66 (58–74)

Table 2.24: Apple of Sodom RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 195 (273–117)

20 Table 2.25: Apple of Sodom estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 1,000,000 5,000 1,000

Apple of Sodom conclusions

In the absence of regional control, the projected total regional damage in net present value is -$1,125,267 over the next 50 years (the minimum projected impact is -$257,779). Managing Apple of Sodom as an Exclusion pest has a projected net benefit to the region of - $5,636,689. Since this is negative, this means that this management scenario does not meets the requirements of Section 72(1a) of the Act. Managing Apple of Sodom as a Control pest has a projected net benefit to the region of $1,016,386. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Apple of Sodom as an Advisory pest has a projected net benefit to the region of $1,083,808. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Apple of Sodom, Control, therefore meets the requirements of Section 72(1a) of the Act.

21 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 78 0.4 Potential extent (ha): 55,049

(19,374−−90,723) Proportion extent of maximum 0.2 Time to potential (yr): 125

Current prop. of potential: 0.002 0.0

0 20 40 60 80 100 120

Years from present

Figure 2.5: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

22 Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory control

● ● ● ● 1.0 1.0 ● ● ● ● 3.5 ● ● ● ● ● ● ● ● ● ● ● ● 250 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 3.0 0.8 ● 0.8 200 ● 2.5 ●

● 0.6 ● 0.6 150 2.0 ● ● ● ●

● ● ● ● 1.5 ● 0.4 0.4 100 ● ● ● ● ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● 1.0 ● ● ● ● ● 0.2 0.2 50 ● ● ● ● ● 0.5 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

● 0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5 ● Years from present Years from present Years from present Years from present

●

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control ● 23

1.0 ● 1.0 ● 1.0 ● 250 Discount rate: 0.08 ●

Total multiplier: 108.15 0.8 0.8 ● 0.8 200 ● ● (92−−149) ● ● ● 0.6 0.6 0.6 150 ● ● ● ●

● ● ● 100 0.4 0.4 ● 0.4 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● ● ● 0.2 0.2 ● 0.2 50 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.6: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.4 Asiatic knotweed (Reynoutria japonica)

Proposed RPMS Category: Control Overall impact: Major

Table 2.26: Relevant biology

Attribute Description Form Thicket forming, rhizomatous herb up to 2 m tall. Habitat Roadsides, riverbanks and waste places. Regional distribution Rotorua area, Te Puke area. Competitive ability Can be competitive in localised areas. Reproductive ability Produces viable seed. Dispersal methods Water, contaminated soil. Also spreads by rhizomes. Resistance to control Can be controlled with herbicides.

Table 2.27: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity L H Forms dense, long-lived thickets, excludes 1, 2 other species, prevents recruitment. Threatened species - H 1, 2 Soil resources - L 3 Water quality - H Blocks up waterways. 3 Production - M Forms dense, long-lived thickets, excludes 1, 2 other species. International trade - - 4 Human health - - 4 Recreation - H Obstructs access to waterways for ﬁshing, 3 swimming, kayaking etc. M¯aoriculture - H See Recreation. 3 Source: 1: Craw (2000), 2: Environment Bay of Plenty (2005b), 3: Senior (2009), 4: Severinsen (2003)

24 Asiatic knotweed CBA results

Table 2.28: Asiatic knotweed CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 1,170,331 0 0 -1,170,331 (320,671–5,348,647) (-320,671 – -5,348,647) Exclusion Pest 12 1,170,319 5,059,979 -3,889,660 (2–19) (320,669–5,348,628) (-4,739,310 – 288,649) Control Pest 31 1,170,300 198,182 972,118 (6–54) (320,665–5,348,593) (122,483 – 5,150,411) Advisory Pest 14 1,170,317 13,212 1,157,105 (3–23) (320,668–5,348,624) (307,456 – 5,335,412)

Table 2.29: Asiatic knotweed CBA base assumptions.

Base assumptions Values Current area infested (ha) 6 Total area potentially infested (ha) 103,636 (35,026–172,246) Years from naturalisation to total area 75 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 0.1 (0.1–0.83) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.30: Asiatic knotweed RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 0.7 (0–1.5)

Table 2.31: Asiatic knotweed RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 4 (3–4)

Table 2.32: Asiatic knotweed RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5

25 Final area infested (ha) 8 (6–9)

Table 2.33: Asiatic knotweed estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 750,000 15,000 1,000

Asiatic knotweed conclusions

In the absence of regional control, the projected total regional damage in net present value is -$1,170,331 over the next 50 years (the minimum projected impact is -$320,671). Managing Asiatic knotweed as an Exclusion pest has a projected net benefit to the region of - $3,889,660. Since this is negative, this means that this management scenario does not meets the requirements of Section 72(1a) of the Act. Managing Asiatic knotweed as a Control pest has a projected net benefit to the region of $972,118. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Asiatic knotweed as an Advisory pest has a projected net benefit to the region of $1,157,105. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Asiatic knotweed, Control, therefore meets the requirements of Section 72(1a) of the Act.

26 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 6 0.4 Potential extent (ha): 103,636

(35,026−−172,246) Proportion extent of maximum 0.2 Time to potential (yr): 75

Current prop. of potential: <0.01 0.0

0 20 40 60

Years from present

Figure 2.7: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

27 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

●

● ● ● 1.0 1.0 ● ● 1.0 ● ● ● ● ● ● 25000 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.8 0.8 ● ● 0.8 ● ● ● ● 20000 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.6 ● 0.6 0.6 15000 ●

0.4 ● 0.4 0.4 10000 ● ● ● ● ● ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● ● ● ● ● ● ● 0.2 0.2 0.2 5000 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 28

1.0 ● 1.0 ● 1.0 ● 25000 Discount rate: 0.08 ● ● ● ● ● Total multiplier: 6512.52 0.8 0.8 0.8 ● ● ● 20000 (3919−−19267) ● ● ● 0.6 0.6 ● 0.6 15000 ●

● ●

●

● ● 0.4 0.4 ● 0.4 10000 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● ● ● 0.2 0.2 ● 0.2 5000 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.8: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.5 Banana passionfruit (Passiﬂora tripartita var.mollissima, P. tarmini- ana, P. caerulea)

Proposed RPMS Category: Advisory Overall impact: Moderate

Table 2.34: Relevant biology

Attribute Description Form Vigorous high climbing vine. Three-lobed leaves large hanging pink star- shaped ﬂowers, which become a yellow oval fruit. Habitat Margins of forest, wind breaks, orchard shelterbelts, usually close to habitation. Also on roadsides, wasteland and open coastal forest. Regional distribution Found in all parts of the region. Competitive ability Plants are shade intolerant but tolerant of physical damage and grazing. In wet areas damage by fungus, Pythiums and slugs may decrease establishment success. Very rapid growth rate. Seeds require high light for germination. Reproductive ability Low percentage of seeds develop to maturity, but if a pollinator were introduced this rate would increase dramatically. Dispersal methods Dispersed by possums and birds that peck at fallen fruit. Overseas evidence shows mainly dispersed by pigs, cattle and pheasants. Also spread by humans who discard partly eaten fruit or who grow it for its fruit. Resistance to control Plants can be hand-pulled when young but regrowth needs to be sprayed with 2% glyphosate. Biocontrol possibilities being investigated in Hawaii. Beneﬁts Edible fruit.

Table 2.35: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity L H Smothers canopy, prevents recruitment. 1, 2 Allows faster-growing or tougher vines to succeed it in dominating canopy. Threatened species L M 1, 2 Soil resources - - 3 Water quality - - 3 Production - L Smothers trees in plantation forests, cre- 1, 4, 5 ates safety hazard during harvest of plantation trees. International trade - - 3 Human health - - 3 Recreation - L Dense walls of vines obstruct access to for- 3 est. M¯aoriculture - L See Recreation. 3 Source: 1: Craw (2000), 2: Williams & Buxton (1995), 3: Severinsen (2003), 4: Roy et al. (2004), 5: Anon. (2007a)

29 Banana passionfruit CBA results

Table 2.36: Banana passionfruit CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 86,588 0 0 -86,588 (29,167–373,714) (-29,167 – -373,714) Exclusion Pest 39 86,549 6,746,639 -6,660,090 (8–65) (29,159–373,649) (-6,717,480 – -6,372,990) Control Pest 111 86,477 264,243 -177,766 (22–194) (29,145–373,520) (-235,098 – 109,277) Advisory Pest 51 86,537 26,424 60,113 (9–96) (29,158–373,618) (2,734 – 347,194)

Table 2.37: Banana passionfruit CBA base assumptions.

Base assumptions Values Current area infested (ha) 20 Total area potentially infested (ha) 99,372 (33,602–165,143) Years from naturalisation to total area 100 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 0.1 (0.1–0.83) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.38: Banana passionfruit RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 2.5 (0–5)

Table 2.39: Banana passionfruit RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 18 (15–20)

Table 2.40: Banana passionfruit RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5

30 Final area infested (ha) 28 (30–25)

Table 2.41: Banana passionfruit estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 1,000,000 20,000 2,000

Banana passionfruit conclusions

In the absence of regional control, the projected total regional damage in net present value is -$86,588 over the next 50 years (the minimum projected impact is -$29,167). Managing Banana passionfruit as an Exclusion pest has a projected net benefit to the region of -$6,660,090. Since this is negative, this means that this management scenario does not meets the requirements of Section 72(1a) of the Act. Managing Banana passionfruit as a Control pest has a projected net benefit to the region of - $177,766. Since this is negative, this means that this management scenario does not meet the requirements of Section 72(1a) of the Act. Managing Banana passionfruit as an Advisory pest has a projected net benefit to the region of $60,113. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Banana passionfruit, Advisory, therefore meets the requirements of Section 72(1a) of the Act.

31 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 20 0.4 Potential extent (ha): 99,372

(33,602−−165,143) Proportion extent of maximum 0.2 Time to potential (yr): 100

Current prop. of potential: <0.01 0.0

0 20 40 60 80 100

Years from present

Figure 2.9: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

32 Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory control

● ● ● ● ● ● ● 1.0 1.0 ● ● ● ● 1.5 ● ● ● ● ● ● ● ● 4000 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

● 0.8 ● 0.8 ●

3000 ● ● 1.0 ● 0.6 ● 0.6

● 2000 0.4 ● 0.4

● ● ● 0.5 ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● 1000 ● ● ● ● ● 0.2 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 33

1.0 ● 1.0 ● 1.0 ● 4000

● ● ● Discount rate: 0.08 ● ● ●

Total multiplier: 636.91 0.8 0.8 ● 0.8 ● 3000 ● (399−−1882) ● ● ● 0.6 0.6 0.6 ●

● ● 2000 ● ●

● ● 0.4 0.4 ● 0.4 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● 1000 ● ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.10: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.6 Blackberry (Rubus fruticosus agg.)

Proposed RPMS Category: Advisory Overall impact: Moderate

Table 2.42: Relevant biology

Attribute Description Form A prickly scrambling, perennial shrub, spiny prickles surround the stem and on the underside of the leaf along the mid-rib. Leaves are oval with jagged edges. Flowers are white to pink in clusters. Fruit are black, ﬂeshy and edible. Habitat Lightly grazed areas, wasteland, particularly where rainfall is high. Regional distribution Widespread and abundant throughout the region. Competitive ability If unchecked, plants can spread and form impenetrable thickets, excluding plants underneath. Reproductive ability Seeds freely and regularly. 7000-13,000 seeds/m2 have been recorded in Australia. Dispersal methods Fleshy fruit are eaten by birds, which disperse the seeds. Resistance to control Not considered the threat it was due to advances in mechanical/chemical control. Beneﬁts Edible fruit.

Table 2.43: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity M H Forms impenetrable thickets, smothers 1, 2 most low-growing species, inhibiting recruitment. Threatened species L M 1 Soil resources - - 3 Water quality - - 3 Production L H Stock movement is hindered by dense 1, 2 thickets. Can degrade wool and hides. International trade - - 3 Human health - - 3 Recreation M M Prickly spines restrict access. 2 M¯aoriculture - L Restricts access to cultural sites (e.g. 1 waahi tapu, urupa). Source: 1: Craw (2000), 2: Environment Bay of Plenty (2005c), 3: Severinsen (2003)

34 Blackberry CBA results

Table 2.44: Blackberry CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 1,439,329,161 0 0 -1,439,329,161 (497,445,080–886,721,947) (-497,445,080 – -886,721,947) Exclusion Pest 63,453,398 1,375,875,763 21,707,311 1,354,168,452 (14,364,018–104,035,028) (483,081,062–782,686,919) (461,373,751 – 760,979,608) Control Pest 167,966,470 1,271,362,691 850,203 1,270,512,488 (36,145,907–291,499,519) (461,299,173–595,222,428) (460,448,970 – 594,372,225) Advisory Pest 69,984,400 1,369,344,761 13,212 1,369,331,549 (14,605,109–125,363,690) (482,839,971–761,358,257) (482,826,759 – 761,345,045)

Table 2.45: Blackberry CBA base assumptions.

Base assumptions Values Current area infested (ha) 611,065 Total area potentially infested (ha) 139,509 (47,022–231,995) Years from naturalisation to total area 100 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 24.38 (5.09–43.68) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.46: Blackberry RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 76,383.1 (0–152,766.2)

Table 2.47: Blackberry RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 381,916 (305,532–458,299)

Table 2.48: Blackberry RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 611,065 (611,065–611,065)

35 Table 2.49: Blackberry estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 3,217,500 64,350 1,000

Blackberry conclusions

In the absence of regional control, the projected total regional damage in net present value is -$1,439,329,161 over the next 50 years (the minimum projected impact is -$497,445,080). Managing Blackberry as an Exclusion pest has a projected net benefit to the region of $1,354,168,452. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Blackberry as a Control pest has a projected net benefit to the region of $1,270,512,488. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Blackberry as an Advisory pest has a projected net benefit to the region of $1,369,331,549. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Blackberry, Advisory, therefore meets the requirements of Section 72(1a) of the Act.

36 Calibrated logistic growth curve 1.0 0.8 0.6 0.4 Proportion extent of maximum 0.2 0.0

0 10 20 30 40 50

Years from present

Figure 2.11: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

37 ● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory control

● ● ● ● ● ● ● ● ● ● 1.0 1.0 ● ● 1.0 ● ● ● ● ● ● ● ● 2.5 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.8 0.8 ● ● 0.8 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 2.0 0.6 ● 0.6 0.6

●

● 0.4 ● 0.4 0.4

1.5 ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area

● 0.2 0.2 0.2 ●

●

● 1.0 ● 0.0 0.0 0.0

● 0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

● Years from present Years from present Years from present Years from present

●

● Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control ● 38

● 1.0 ● 1.0 ● 1.0 ●

2.5 ● Discount rate: 0.08 ● ● ●

● Total multiplier: 96.6 0.8 0.8 0.8 ● ● ●

2.0 ● ● (160−−33) ● ● ● ● ● ● ● ● ● 0.6 0.6 0.6 ● 1.5 ● ● ● ●

● ● ● ● ● ● ● ● 0.4 0.4 0.4 1.0 ● ● ● ● ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● ● ● ● ● ● ● ● ● 0.2 0.2 ● 0.2 0.5 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0 ● ● ● ● ● 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.12: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.7 Boneseed (Chrysanthemoides monilifera)

Proposed RPMS Category: Control Overall impact: Major

Table 2.50: Relevant biology

Attribute Description Form Bushy, much branched shrub growing to 3 m tall. Habitat Coastal cli↵s, waste places, consolidated dunes and scrubland. Regional distribution Isolated infestations along the coast. Competitive ability Plants are tolerant of low fertility and drought, but intolerant of shade and wet. Plant is ﬁre-adapted with seed germination stimulated by ﬁre events. Fast shoot growth. Can spread by layering, forming pure stands. Reproductive ability 5000 seeds produced per plant, viable for up to 10 years. Dispersal methods Birds disperse seeds. Resistance to control Tolerant of some physical damage. Can be controlled with brush weed killers but leaves a large seed bank. This plant is the highest priority for biological control in Australia.

Table 2.51: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity M H Colonises disturbed sites faster than na- 1, 2 tive species, rapidly replaces other species under 2 m, prevents recruitment. Creates heavy shade where high light levels should occur. Threatened species L H Could threaten rare coastal shrubs. 1 Soil resources L L Causes erosion. 3, 4 Water quality - - 5 Production L L Forms dense impenetrable stands. 5 International trade - - 5 Human health - L Highly ﬂammable. Fire risk near housing. 5 Recreation L L Dense stands obstruct access in coastal ar- 2 eas. M¯aoriculture L M A nuisance at Te Whare pa near Ohope. 3, 5 Source: 1: Craw (2000), 2: ECan (2003), 3: Mather (2009), 4: Stahl (2009), 5: Severinsen (2003)

39 Boneseed CBA results

Table 2.52: Boneseed CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 46,304 0 0 -46,304 (11,188–115,525) (-11,188 – -115,525) Exclusion Pest 888 45,416 2,529,990 -2,484,574 (267–1,400) (10,921–114,125) (-2,519,069 – -2,415,865) Control Pest 2,278 44,026 99,091 -55,065 (672–3,671) (10,516–111,854) (-88,575 – 12,763) Advisory Pest 1,144 45,160 13,212 31,948 (302–2,065) (10,886–113,460) (-2,326 – 100,248)

Table 2.53: Boneseed CBA base assumptions.

Base assumptions Values Current area infested (ha) 30 Total area potentially infested (ha) 23,859 (9,393–38,324) Years from naturalisation to total area 125 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 6.95 (1.93–11.98) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.54: Boneseed RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 3.8 (0–7.5)

Table 2.55: Boneseed RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 15 (8–22)

Table 2.56: Boneseed RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 41 (45–38)

40 Table 2.57: Boneseed estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 375,000 7,500 1,000

Boneseed conclusions

In the absence of regional control, the projected total regional damage in net present value is -$46,304 over the next 50 years (the minimum projected impact is -$11,188). Managing Boneseed as an Exclusion pest has a projected net benefit to the region of -$2,484,574. Since this is negative, this means that this management scenario does not meets the requirements of Section 72(1a) of the Act. Managing Boneseed as a Control pest has a projected net benefit to the region of -$55,065. Since this is negative, this means that this management scenario does not meet the requirements of Section 72(1a) of the Act. Managing Boneseed as an Advisory pest has a projected net benefit to the region of $31,948. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Boneseed, Control, therefore fails to meet the requirements of Section 72(1a) of the Act. However, that conclusion is only based on the average results from the CBA. A closer look shows that the uncertainty around the net benefit of placing boneseed in the control category is mostly positive (i.e., there is a net benefit). This means that the CBA results are uncertain about whether the proposed level of expenditure is likely to be cost beneficial but there is a reasonably large probability that it will be. This typically reflects inadequate knowledge of the economic value of weed impacts, especially for impacts outside of agriculture which are inherently harder to quantify (as is the case here for boneseed). We recommend a precautionary approach to these weeds, meaning that they should be managed in their proposed categories if adequate funding is available. When dealing with expanding weed populations, early action is the far and away the most cost e↵ective approach even when there is inadequate knowledge of impacts (Harris & Timmins 2009). For these reasons, it is entirely appropriate to use these CBA results to justify the management of boneseed as a Control pest under section 72(1a) of the Act.

41 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 30 0.4 Potential extent (ha): 23,859

(9,393−−38,324) Proportion extent of maximum 0.2 Time to potential (yr): 125

Current prop. of potential: 0.002 0.0

0 20 40 60 80 100 120

Years from present

Figure 2.13: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

42 Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory control

● ● ● 1.0 1.0 ● 1.5 ● ● ● ● ● ● ● ● ● ● 250 ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.8 0.8 ● ● ● ● ● ● ● ● ● ● 200 ● ● ● ● ● ● ● ● 1.0 ● ● ● ● ● ● ● ● 0.6 0.6 ● ● ● ● ● ● ● 150 ● ● ● ● ● ●

● ● ● 0.4 0.4 100 ● ● ● 0.5 ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● ● ● ● ● ● 0.2 0.2 50 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 43

1.0 ● 1.0 ● 1.0 ●

● ● ● 250 Discount rate: 0.08 ● ● ● Total multiplier: 115.28 0.8 0.8 0.8 ● ●

200 ● (99−−153)

● ● 0.6 0.6 ● 0.6 ● 150 ● ●

●

● ● 0.4 0.4 ● 0.4 100 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● ● 0.2 0.2 ● 0.2 ● ● 50 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 ● ● ● 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.14: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.8 Cathedral bells (Cobaea scandens)

Proposed RPMS Category: Advisory Overall impact: Moderate

Table 2.58: Relevant biology

Attribute Description Form Vigorous perennial climber growing to canopy height. Climbs by hooked tendrils. Bell-shaped purple ﬂowers followed by oval pods. Habitat Garden escape that can smother trees, shrubs and riverside cli↵s. Regional distribution A number of sites throughout the region. Competitive ability High fast growing and foliage can smother supporting plants. Reproductive ability High seeds proliﬁcally and seed can germinate throughout most of the year. Dispersal methods Wind or water borne seed. Resistance to control Easily controlled by spraying with herbicide.

Table 2.59: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity M H Smothers all plants up to medium-high 1, 2 canopy, prevents recruitment. Threatened species L M 1, 2 Soil resources - - 3 Water quality - - 3 Production - L Smothers trees in plantation forests. 2 International trade - - 3 Human health - - 3 Recreation L L Dense walls of vines obstruct access to for- 2 est. M¯aoriculture - M See Recreation. 3 Source: 1: Craw (2000), 2: Anon. (2007b), 3: Severinsen (2003)

44 Cathedral bells CBA results

Table 2.60: Cathedral bells CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 96,587 0 0 -96,587 (30,639–419,773) (-30,639 – -419,773) Exclusion Pest 124 96,463 6,746,639 -6,650,176 (46–189) (30,593–419,584) (-6,716,046 – -6,327,055) Control Pest 329 96,258 264,243 -167,985 (115–529) (30,524–419,244) (-233,719 – 155,001) Advisory Pest 152 96,435 13,212 83,223 (57–228) (30,582–419,545) (17,370 – 406,333)

Table 2.61: Cathedral bells CBA base assumptions.

Base assumptions Values Current area infested (ha) 10 Total area potentially infested (ha) 98,312 (33,316–163,308) Years from naturalisation to total area 100 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 2.92 (0.99–4.84) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.62: Cathedral bells RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 1.2 (0–2.5)

Table 2.63: Cathedral bells RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 6 (5–8)

Table 2.64: Cathedral bells RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 12 (10–15)

45 Table 2.65: Cathedral bells estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 1,000,000 20,000 1,000

Cathedral bells conclusions

In the absence of regional control, the projected total regional damage in net present value is -$96,587 over the next 50 years (the minimum projected impact is -$30,639). Managing Cathedral bells as an Exclusion pest has a projected net benefit to the region of - $6,650,176. Since this is negative, this means that this management scenario does not meets the requirements of Section 72(1a) of the Act. Managing Cathedral bells as a Control pest has a projected net benefit to the region of -$167,985. Since this is negative, this means that this management scenario does not meet the requirements of Section 72(1a) of the Act. Managing Cathedral bells as an Advisory pest has a projected net benefit to the region of $83,223. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Cathedral bells, Advisory, therefore meets the requirements of Section 72(1a) of the Act.

46 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 10 0.4 Potential extent (ha): 98,312

(33,316−−163,308) Proportion extent of maximum 0.2 Time to potential (yr): 100

Current prop. of potential: <0.01 0.0

0 20 40 60 80 100

Years from present

Figure 2.15: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

47 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

●

● ● ● 1.0 1.0 ● ● 1.0 ● ● 8000 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.8 0.8 ● ● 0.8 ● ● ● ● ● ● 6000 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.6 ● 0.6 0.6

● 4000

0.4 ● 0.4 0.4

● ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● 2000 ● ● ● ● ● 0.2 0.2 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 48

● ● ● 8000 1.0 1.0 1.0

Discount rate: 0.08 ● ● ● ● ● Total multiplier: 1261.45 0.8 0.8 0.8 ● ● ● 6000 (760−−3720) ● ● ● 0.6 0.6 ● 0.6 ●

● ●

4000 ●

● ● 0.4 0.4 ● 0.4 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● 2000 ● ● ● ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.16: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.9 Chilean rhubarb (Gunnera tinctoria)

Proposed RPMS Category: Control Overall impact: Moderate

Table 2.66: Relevant biology

Attribute Description Form Summer green herb with massive prickly umbrella-like leaves up to 2 m long. Looks like very large rhubarb. Habitat Can inhabit coastal cli↵s, riparian margins and wetlands. Regional distribution Uncertain, but occasionally found naturalised in close proximity to set- tlements. Competitive ability Large spreading leaves shade out other species. Reproductive ability Produces viable seed. Dispersal methods Has been cultivated in gardens, now spreading by water-borne seed and fragments. Resistance to control Unknown.

Table 2.67: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity L H Forms dense colonies and displaces native 1, 2 vegetation. Threatened species - M Has invaded coastal cli↵s in Taranaki 1, 2 which are home to a number of low- growing endangered plants. Soil resources - - 3 Water quality - - 3 Production - - 3 International trade - - 3 Human health - - 3 Recreation - M Obstructs access to waterways. 2 M¯aoriculture - M See Recreation. 2 Source: 1: BSNZ (2009), 2: Anon. (2006b), 3: Severinsen (2003)

49 Chilean rhubarb CBA results

Table 2.68: Chilean rhubarb CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 250,774 0 0 -250,774 (98,762–998,333) (-98,762 – -998,333) Exclusion Pest 2 250,772 1,686,660 -1,435,888 (0–4) (98,762–998,329) (-1,587,898 – -688,331) Control Pest 6 250,768 66,061 184,707 (1–10) (98,761–998,323) (32,700 – 932,262) Advisory Pest 3 250,771 13,212 237,559 (1–4) (98,761–998,329) (85,549 – 985,117)

Table 2.69: Chilean rhubarb CBA base assumptions.

Base assumptions Values Current area infested (ha) 1 Total area potentially infested (ha) 103,808 (35,083–172,532) Years from naturalisation to total area 75 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 0.52 (0.1–0.94) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.70: Chilean rhubarb RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 0.1 (0–0.2)

Table 2.71: Chilean rhubarb RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 1 (0–1)

Table 2.72: Chilean rhubarb RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5

50 Final area infested (ha) 1 (1–2)

Table 2.73: Chilean rhubarb estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 250,000 5,000 1,000

Chilean rhubarb conclusions

In the absence of regional control, the projected total regional damage in net present value is -$250,774 over the next 50 years (the minimum projected impact is -$98,762). Managing Chilean rhubarb as an Exclusion pest has a projected net benefit to the region of - $1,435,888. Since this is negative, this means that this management scenario does not meets the requirements of Section 72(1a) of the Act. Managing Chilean rhubarb as a Control pest has a projected net benefit to the region of $184,707. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Chilean rhubarb as an Advisory pest has a projected net benefit to the region of $237,559. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Chilean rhubarb, Control, therefore meets the requirements of Section 72(1a) of the Act.

51 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 1 0.4 Potential extent (ha): 103,808

(35,083−−172,532) Proportion extent of maximum 0.2 Time to potential (yr): 75

Current prop. of potential: <0.01 0.0

0 20 40 60

Years from present

Figure 2.17: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

52 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

●

● ● ● 1.0 1.0 ● ● 1.0 ● ● ● ● ● ● 150000 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.8 0.8 ● ● 0.8 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 100000 ● 0.6 0.6 0.6

●

0.4 ● 0.4 0.4

● ● ● ● ● ● 50000 ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● ● ● ● ● ● ● 0.2 0.2 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 53

1.0 ● 1.0 ● 1.0 ● 150000 Discount rate: 0.08 ● ● ● ● ● Total multiplier: 39134.14 0.8 0.8 0.8 ● ● ●

(23546−−115791) ● ● 100000 ● 0.6 0.6 ● 0.6 ●

● ●

●

● ● 0.4 0.4 ● 0.4 ● ● ● 50000 ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● ● ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.18: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.10 Climbing spindleberry (Celastrus orbiculatus)

Proposed RPMS Category: Control Overall impact: Major

Table 2.74: Relevant biology

Attribute Description Form A deciduous climber that can grow to 12 m high. Produces yellow fruit, which open to expose a scarlet centre. Habitat Forest margins, scrub and gardens. Regional distribution Rotorua area, isolated sites in other parts of the region. Competitive ability Can smother and out-compete native species. Reproductive ability Produces viable seed. Dispersal methods Has been planted in some areas as an ornamental, its seeds are also dispersed by birds. Resistance to control Can be controlled using foliar or stump application of herbicide.

Table 2.75: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity M H Stems strangle host, overtop most 1, 2 canopies and cause collapse. Threatened species - H 1, 2 Soil resources - - 3 Water quality - - 3 Production L M Smothers trees in plantation forests, cre- 2, 4 ates safety hazard during harvest of plantation trees. Can damage shelterbelts. International trade - - 3 Human health - - 3 Recreation L M Layering stems become dense and obstruct 1, 2 access to forest. M¯aoriculture L M See Recreation. 1 Source: 1: Craw (2000), 2: Anon. (2004a), 3: Severinsen (2003), 4: Stahl (2009)

54 Climbing spindleberry CBA results

Table 2.76: Climbing spindleberry CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 928,301 0 0 -928,301 (201,091–4,557,817) (-201,091 – -4,557,817) Exclusion Pest 296 928,005 3,373,319 -2,445,314 (91–465) (201,000–4,557,352) (-3,172,319 – 1,184,033) Control Pest 784 927,517 132,122 795,395 (229–1,303) (200,862–4,556,514) (68,740 – 4,424,392) Advisory Pest 363 927,938 13,212 914,726 (113–560) (200,978–4,557,257) (187,766 – 4,544,045)

Table 2.77: Climbing spindleberry CBA base assumptions.

Base assumptions Values Current area infested (ha) 12 Total area potentially infested (ha) 133,916 (44,703–223,128) Years from naturalisation to total area 100 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 5.79 (1.64–9.94) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.78: Climbing spindleberry RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 1.5 (0–3)

Table 2.79: Climbing spindleberry RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 8 (6–9)

Table 2.80: Climbing spindleberry RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5

55 Final area infested (ha) 15 (12–18)

Table 2.81: Climbing spindleberry estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 500,000 10,000 1,000

Climbing spindleberry conclusions

In the absence of regional control, the projected total regional damage in net present value is -$928,301 over the next 50 years (the minimum projected impact is -$201,091). Managing Climbing spindleberry as an Exclusion pest has a projected net benefit to the region of -$2,445,314. Since this is negative, this means that this management scenario does not meets the requirements of Section 72(1a) of the Act. Managing Climbing spindleberry as a Control pest has a projected net benefit to the region of $795,395. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Climbing spindleberry as an Advisory pest has a projected net benefit to the region of $914,726. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Climbing spindleberry, Control, therefore meets the requirements of Section 72(1a) of the Act.

56 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 12 0.4 Potential extent (ha): 133,916

(44,703−−223,128) Proportion extent of maximum 0.2 Time to potential (yr): 100

Current prop. of potential: <0.01 0.0

0 20 40 60 80 100

Years from present

Figure 2.19: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

57 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

●

● ● ● 1.0 1.0 ● ● 1.0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 8000 ● ● ● ● ● ● ● ● ● ● ● 0.8 0.8 ● ● 0.8 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 6000 ● ● 0.6 ● 0.6 0.6

●

4000 ● 0.4 0.4 0.4

● ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● ● 2000 ● ● ● 0.2 0.2 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 58

1.0 ● 1.0 ● 1.0 ●

Discount rate: 0.08 ● ● 8000 ● ● ● Total multiplier: 1414.68 0.8 0.8 0.8 ● ● ●

(849−−4236) ● ● 6000 ● 0.6 0.6 ● 0.6 ●

● ●

●

● 4000 ● 0.4 0.4 ● 0.4 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● ● 2000 ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.20: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.11 Coast tea tree (Leptospermum laevigatum)

Proposed RPMS Category: Control Overall impact: Major

Table 2.82: Relevant biology

Attribute Description Form Tall, bushy shrub or small, twisted tree, to 6 m. Leaves are grey-green, obovate, to 2 cm. Flowers are white, to 1.5 cm diameter, in spring or early summer. Habitat Coastal sand dunes, shrubland. Regional distribution Matakana Island. Competitive ability Highly tolerant of salt spray. Reproductive ability Woody capsules shed large numbers of seeds. Dispersal methods Gravity, wind. Deliberately planted for sand stabilisation. Resistance to control Unknown. Beneﬁts Minor beneﬁt to production (forestry) as it bu↵ers a pine plantation from salt spray on Matakana Island.

Table 2.83: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity H H Excludes native sand-binders (pingao and 1, 2, 3 spinifex), alters sand-dune community. Threatened species M H Displaces Pimelia arenaria in sand dunes. 3, 4 Soil resources L H Exacerbates fore dune erosion, as it ex- 3 cludes native sand-binders and its roots do not bind sand.. Water quality - - 3 Production - - 5 International trade - - 6 Human health - - 6 Recreation L M Blocks access to beaches and sand dunes. 3 M¯aoriculture L M See Recreation. 3 Source: 1: Williams et al. (2005), 2: Hicks et al. (2001), 3: Stahl (2009), 4: de Lange et al. (2009), 5: Anon. (2010c), 6: Severinsen (2003)

59 Coast tea tree CBA results

Table 2.84: Coast tea tree CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 702,429 0 0 -702,429 (302,844–2,784,693) (-302,844 – -2,784,693) Exclusion Pest 885 701,544 674,664 26,880 (633–1,087) (302,211–2,783,606) (-372,453 – 2,108,942) Control Pest 2,344 700,085 26,424 673,661 (1,593–3,045) (301,251–2,781,648) (274,827 – 2,755,224) Advisory Pest 1,086 701,343 13,212 688,131 (788–1,310) (302,056–2,783,383) (288,844 – 2,770,171)

Table 2.85: Coast tea tree CBA base assumptions.

Base assumptions Values Current area infested (ha) 30 Total area potentially infested (ha) 97,434 (32,954–161,915) Years from naturalisation to total area 50 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 6.93 (4.57–9.29) Any beneﬁts provided by the weed 1 Discount rate 0.08

Table 2.86: Coast tea tree RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 3.8 (0–7.5)

Table 2.87: Coast tea tree RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 19 (15–22)

Table 2.88: Coast tea tree RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 38 (30–45)

60 Table 2.89: Coast tea tree estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 100,000 2,000 1,000

Coast tea tree conclusions

In the absence of regional control, the projected total regional damage in net present value is -$702,429 over the next 50 years (the minimum projected impact is -$302,844). Managing Coast tea tree as an Exclusion pest has a projected net benefit to the region of $26,880. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Coast tea tree as a Control pest has a projected net benefit to the region of $673,661. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Coast tea tree as an Advisory pest has a projected net benefit to the region of $688,131. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Coast tea tree, Control, therefore meets the requirements of Section 72(1a) of the Act.

61 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 30 0.4 Potential extent (ha): 97,434

(32,954−−161,915) Proportion extent of maximum 0.2 Time to potential (yr): 50

Current prop. of potential: 0.001 0.0

0 10 20 30 40 50

Years from present

Figure 2.21: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

62 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

●

● ● ● 1.0 1.0 ● ● 1.0 ● ● ● ● ● ● ● ● 5000 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.8 0.8 ● ● 0.8 ● ● ● ● 4000 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.6 ● 0.6 0.6 3000 ●

0.4 ● 0.4 0.4 2000 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● ● ● ● ● ● 0.2 0.2 0.2 1000 ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 63

1.0 ● 1.0 ● 1.0 ● 5000 Discount rate: 0.08 ● ● ● ● ● Total multiplier: 3378.25 0.8 0.8 0.8 ● ● ● 4000 (2210−−9986) ● ● ● 0.6 0.6 ● 0.6 3000 ● ● ●

●

● ● 0.4 0.4 ● 0.4 2000 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● ● ● 0.2 0.2 ● 0.2 1000 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.22: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.12 Darwin’s barberry (Berberis darwinii)

Proposed RPMS Category: Control Overall impact: Moderate

Table 2.90: Relevant biology

Attribute Description Form Evergreen shrub up to 4 m tall with holly-like leaves and purple berries. Habitat Shade tolerant, can survive in a variety of habitats. Regional distribution South of Rotorua, otherwise extent unknown. Competitive ability Can form impenetrable stands. May invade forest as it is shade tolerant. Reproductive ability Produces viable seed. Dispersal methods Has been planted as a hedge plant in some areas; birds also disperse the seed. Resistance to control Unknown.

Table 2.91: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity L M Can invade forest as it is shade-tolerant, 1 forms impenetrable thickets and out- competes native forest and shrubland species. Threatened species - M 1 Soil resources - - 2 Water quality - - 2 Production L L Excludes pasture species. Nuisance in 1, 3, 4 plantation forestry. International trade - - 2 Human health - - 2 Recreation - L Prickly spines restrict access. 1 M¯aoriculture - M Obstructs access to cultural sites (e.g. 2 waahi tapu, urupa). Source: 1: Anon. (2006a), 2: Severinsen (2003), 3: Craw (2000), 4: Mallinson (2009)

64 Darwin’s barberry CBA results

Table 2.92: Darwin’s barberry CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 347,282 0 0 -347,282 (62,999–974,067) (-62,999 – -974,067) Exclusion Pest 14,905 332,377 1,011,996 -679,619 (3,234–24,556) (59,765–949,511) (-952,231 – -62,485) Control Pest 39,455 307,827 39,636 268,191 (8,137–68,805) (54,862–905,262) (15,226 – 865,626) Advisory Pest 18,281 329,001 13,212 315,789 (4,024–29,591) (58,975–944,476) (45,763 – 931,264)

Table 2.93: Darwin’s barberry CBA base assumptions.

Base assumptions Values Current area infested (ha) 100 Total area potentially infested (ha) 141,607 (47,641–235,573) Years from naturalisation to total area 125 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 35 (7–63) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.94: Darwin’s barberry RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 12.5 (0–25)

Table 2.95: Darwin’s barberry RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 62 (50–75)

Table 2.96: Darwin’s barberry RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5

65 Final area infested (ha) 125 (100–150)

Table 2.97: Darwin’s barberry estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 150,000 3,000 1,000

Darwin’s barberry conclusions

In the absence of regional control, the projected total regional damage in net present value is -$347,282 over the next 50 years (the minimum projected impact is -$62,999). Managing Darwin’s barberry as an Exclusion pest has a projected net benefit to the region of -$679,619. Since this is negative, this means that this management scenario does not meets the requirements of Section 72(1a) of the Act. Managing Darwin’s barberry as a Control pest has a projected net benefit to the region of $268,191. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Darwin’s barberry as an Advisory pest has a projected net benefit to the region of $315,789. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Darwin’s barberry, Control, therefore meets the requirements of Section 72(1a) of the Act.

66 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 100 0.4 Potential extent (ha): 141,607

(47,641−−235,573) Proportion extent of maximum 0.2 Time to potential (yr): 125

Current prop. of potential: 0.001 0.0

0 20 40 60 80 100 120

Years from present

Figure 2.23: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

67 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

●

● ● ● 1.0 1.0 ● ● 1.0 ● ● ● ● ● ● ● ● 400 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.8 0.8 ● ● 0.8 ● ● ● ● ● ● ● ● ● ● ● 300 ● ● ● ● ● ● ● ● ● ● 0.6 ● 0.6 0.6

● ● 200 ● ● ● ● 0.4 0.4 0.4 ● ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● ● ● 100 ● ● 0.2 0.2 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 68

1.0 ● 1.0 ● 1.0 ● 400 Discount rate: 0.08 ● ● ● ● ● Total multiplier: 132.57 0.8 0.8 0.8 ● ● ●

● 300 (113−−221) ● ● 0.6 0.6 ● 0.6 ●

● ● 200 ● ● ● 0.4 0.4 ● 0.4 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● 100 ● ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.24: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.13 Egeria densa (Egeria densa)

Proposed RPMS Category: Control (deﬁned lakes) Overall impact: Major

Table 2.98: Relevant biology

Attribute Description Form Submerged, bottom-rooting perennial, growing to 5 m. Stems slender, brittle, much-branched, buoyant, 3 mm diam. Leaves in whorls of 4-6 (occ. 3 near base), linear, 15-30 x 4 mm, dark green. Flowers on surface, 3 petalled, 20 mm diam, white with 9 yellow stamens, Nov-Jan. Habitat Rivers, lakes, dunelakes, other waterbodies with mod-high light and 10- 25 degrees C. Regional distribution Lakes Okareka, Rerewhakaaitu, Rotoiti, Rotorua, Tarawera and many other waterbodies. Competitive ability Reproductive ability Grows easily from broken fragments. Only male plants found in NZ, no seed set. Dispersal methods Water, humans. Resistance to control Dicult to control.

Table 2.99: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity M H Forms vast underwater meadows in fresh- 1, 2, 3 water up to 5 m tall, shades out smaller native species, prevents recruitment. Rotting vegetation deoxygenates water, killing fauna and ﬂora. Threatened species L H 1, 2 Soil resources - - Water quality M H Large clumps dislodge, causing blockage 1, 3 and ﬂooding. Rotting vegetation degrades water quality. Causes nutrient release from sediments, exacerbates eutrophica- tion. Production - - 1, 4 International trade - - Human health - L Large weed beds may support more snails 5 which host the waterborne schistosome cercariae larvae that cause ’swimmers itch’. Recreation M H Dense masses block up lakes and shade 1, 2, 3 water, reducing access to lakes. Inconve- nience caused by biosecurity measures i.e. restricted access to lakes by lake cordons, cleaning and washing procedures. M¯aoriculture M H See Recreation. 1, 2, 3 Source: 1: Craw (2000), 2: Roy et al. (2004), 3: Clayton & Champion (2003), 4: Department of Conser- vation (2007), 5: NIWA (2002)

69 Egeria densa CBA results

Since Egeria densa is currently absent from the defined area, it is dicult to accurately quantify the costs and benefits of current and proposed e↵orts to continue to exclude the species. If the species were to invade this year and spread in the defined area, without regional control for the next 50 years, the total pest impacts over this period in net present value are calculated to be $412,940 ($539,742–$442,649). This can be compared with the calculated net present value of the proposed annual expenditure on control over this same period of $408,811 (to exclude the Control pest from the defined areas). Note that this comparison does not take into account whether or not the proposed level of expenditure is adequate to have a high probability of excluding the species over this period. Given the broad experience of the biosecurity sta↵ at Environment Bay of Plenty, we assume that it will be. The following tables provide the parameters used in this cost-benefit analysis.

Table 2.100: Egeria densa CBA base assumptions.

Base assumptions Values Current area infested (ha) 0 Total area potentially infested (ha) 432 (432–432) Years from naturalisation to total area 25 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 7.38 (2.5–12.25) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.101: Egeria densa estimated total annual cost of the proposed RPMS scenario (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Year Total Costs 1.00 30,942

Egeria densa conclusions

Since the calculated average impact should the species establish in the deﬁned area is greater than the anticipated expenditure, and establishment is likely in the absence of regional surveillance and control, this management scenario meets the requirements of Section 72(1a) of the Act.

70 2.1.14 Elodea canadensis (Elodea canadensis)

Proposed RPMS Category: Advisory Overall impact: Major

Table 2.102: Relevant biology

Attribute Description Form Submerged, bottom-rooting perennial, growing to 8+ m. Stems slender, brittle, branched, 1 mm diam. Leaves in whorls of 3 (opposite at base), linear, 6-12 x 2 mm, translucent dark green. Male (very rare) and female ﬂowers on separate plants. Flowers on surface, on long thread-like stalks, 5-petalled, 5 mm diam, white, tinged purple. Habitat Rivers, lakes, dunelakes, other waterbodies with mod-high light and tem- peratures under 28 degrees C. Regional distribution Lakes Okareka, Okaro, Okataina, Rerewhakaaitu, Rotoehu, Rotoiti, Ro- tokakahi, Rotoma, Rotomahana, Rotorua, Tarawera, Tikitapu and many other waterbodies. Competitive ability Tends to be replaced by Lagarosiphon or Egeria if these are introduced into the same waterbody. Reproductive ability Grows easily from broken fragments. No seed set in NZ. Deliberately spread by humans. Dispersal methods Water, humans. Resistance to control Dicult to control.

Table 2.103: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity H H Forms dense masses in freshwater up 1, 2, 3 to 10 m tall (to 10 m deep), shades out native species, prevents recruitment. Rotting vegetation deoxygenates water, killing fauna and ﬂora. Threatened species L H 1, 2 Soil resources - - Water quality M H Large clumps dislodge, causing blockage 1, 3 and ﬂooding. Rotting vegetation degrades water quality. Causes nutrient release from sediments, exacerbates eutrophica- tion. Production - - 1, 4 International trade - - Human health - L Large weed beds may support more snails 5 which host the waterborne schistosome cercariae larvae that cause ’swimmers itch’. Recreation M H Dense masses block up lakes and shade 1, 2, 3 water, reducing access to lakes. Inconve- nience caused by biosecurity measures i.e. restricted access to lakes by lake cordons, cleaning and washing procedures. M¯aoriculture M H See Recreation. 1, 2, 3 continued

71 Table 2.103: Impact evaluation

Category Current Potential Comment Source impact impact Source: 1: Craw (2000), 2: Roy et al. (2004), 3: Clayton & Champion (2003), 4: Department of Conser- vation (2007), 5: NIWA (2002)

72 Elodea canadensis CBA results

Table 2.104: Elodea canadensis CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 347,668 0 0 -347,668 (164,940–988,717) (-164,940 – -988,717) Exclusion Pest 44,875 302,793 4,784,668 -4,481,875 (32,451–54,765) (132,489–933,952) (-4,652,179 – -3,850,716) Control Pest 118,789 228,879 248,055 -19,176 (81,661–153,447) (83,279–835,270) (-164,776 – 587,215) Advisory Pest 55,039 292,629 13,212 279,417 (40,389–65,992) (124,551–922,725) (111,339 – 909,513)

Table 2.105: Elodea canadensis CBA base assumptions.

Base assumptions Values Current area infested (ha) 562 Total area potentially infested (ha) 4,216 (1,405–7,027) Years from naturalisation to total area 50 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 18.75 (12.5–25) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.106: Elodea canadensis RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 70.2 (0–140.5)

Table 2.107: Elodea canadensis RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 351 (281–422)

Table 2.108: Elodea canadensis RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5

73 Final area infested (ha) 702 (562–843)

Table 2.109: Elodea canadensis estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 709,193 18,775 1,000

Elodea canadensis conclusions

In the absence of regional control, the projected total regional damage in net present value is -$347,668 over the next 50 years (the minimum projected impact is -$164,940). Managing Elodea canadensis as an Exclusion pest has a projected net benefit to the region of -$4,481,875. Since this is negative, this means that this management scenario does not meets the requirements of Section 72(1a) of the Act. Managing Elodea canadensis as a Control pest has a projected net benefit to the region of -$19,176. Since this is negative, this means that this management scenario does not meet the requirements of Section 72(1a) of the Act. Managing Elodea canadensis as an Advisory pest has a projected net benefit to the region of $279,417. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Elodea canadensis, Advisory, therefore meets the requirements of Section 72(1a) of the Act.

74 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 562 0.4 Potential extent (ha): 4,216

(1,405−−7,027) Proportion extent of maximum 0.2 Time to potential (yr): 50

Current prop. of potential: 0.24 0.0

−40 −20 0 20 40

Years from present

Figure 2.25: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

75 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

●

● ● ● 1.0 1.0 ● ● 1.0 ● ● ● ● 12 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.8 0.8 ● ● 0.8 10 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 8 0.6 ● 0.6 0.6

●

6 0.4 ● 0.4 0.4

● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 4 ● ● ● ● ● ● ● ● ● ● ● 0.2 0.2 0.2 ● ● ● ● ● ● ● ● 2 ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 76

1.0 ● 1.0 ● 1.0 ● 12 Discount rate: 0.08 ● ● ● ● ● 10 Total multiplier: 32.99 0.8 0.8 0.8 ● ● ●

(23−−70) ● ● 8 ● 0.6 0.6 ● 0.6 ●

● ● 6 ● ● ● 0.4 0.4 ● 0.4 ● ● ● 4 ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● ● ● 0.2 0.2 ● 0.2 ● ● ● 2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 ● ● ● ● 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.26: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.15 Gorse (Ulex europaeus)

Proposed RPMS Category: Advisory Overall impact: Moderate

Table 2.110: Relevant biology

Attribute Description Form Sharply spiny perennial shrub up to 4 m tall, leaves reduced to a spine- like tip with a very deep tap root and extensive lateral roots. Habitat Grasslands, shrubland, forest margins, hill country, coastal habitats, wastelands, optimum growth on low fertility soils. Regional distribution Widespread throughout region. Competitive ability Fast growth and being a nitrogen ﬁxer means it can compete e↵ectively with tree seedlings. Reproductive ability Seeds have hard coat, can be dormant for up to 30 years. Huge seed bank in soil (estimated 20,000 seeds/m2). Dispersal methods Most seeds fall close to parent plant but may be ejected up to 6 m. Also spread by water, birds, road making gravel and machinery. Resistance to control Dicult to control on infertile and steep land, best controlled by com- bination of methods. Beneﬁts Can increase soil nitrogen and act as a nursery crop to facilitate regeneration of native forest on cleared land.

Table 2.111: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity L M Forms dense stands, out-competes low- 1, 2, 3, growing species. Increases soil nitrogen, 4, 5, 6 may induce succession to forest, to the detriment of specialised plants (e.g. herbs, orchids, low ferns). Native forest succession through gorse is vegetatively di↵erent and of lower diversity than succession through kanuka. Threatened species - M 4 Soil resources - - 7 Water quality L L Increases nitrogen leaching into water- 4 ways. Production M H Spines pull ﬂeece and lower value of wool. 3, 4, 5, 8 International trade - - 7 Human health - - 7 Recreation M M Prickly spines restrict access. 7 M¯aoriculture - L Restricts access to cultural sites (e.g. 4 waahi tapu, urupa). Source: 1: Lee et al. (1986), 2: Hill et al. (2001), 3: Williams & Timmins (2002), 4: Craw (2000), 5: Environment Bay of Plenty (2005d), 6: Sullivan et al. (2007), 7: Severinsen (2003), 8: Roy et al. (2004)

77 Gorse CBA results

Table 2.112: Gorse CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 229,103,366 0 0 -229,103,366 (57,016,320–934,996,589) (-57,016,320 – -934,996,589) Exclusion Pest 51,088,840 178,014,526 20,644,715 157,369,811 (17,335,202–84,842,477) (39,681,118–850,154,112) (19,036,403 – 829,509,397) Control Pest 98,094,788 131,008,578 808,584 130,199,994 (32,550,971–166,497,158) (24,465,349–768,499,431) (23,656,765 – 767,690,847) Advisory Pest 40,593,016 188,510,350 26,424 188,483,926 (12,537,482–73,463,106) (44,478,838–861,533,483) (44,452,414 – 861,507,059)

Table 2.113: Gorse CBA base assumptions.

Base assumptions Values Current area infested (ha) 55,770 Total area potentially infested (ha) 173,453 (57,885–289,022) Years from naturalisation to total area 25 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 137.96 (46.81–229.12) Any beneﬁts provided by the weed 1 Discount rate 0.08

Table 2.114: Gorse RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 52,981.5 (52,981.5–52,981.5)

Table 2.115: Gorse RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 64,136 (69,712–58,558)

Table 2.116: Gorse RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 71,107 (83,655–58,558)

78 Table 2.117: Gorse estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 3,060,000 61,200 2,000

Gorse conclusions

In the absence of regional control, the projected total regional damage in net present value is -$229,103,366 over the next 50 years (the minimum projected impact is -$57,016,320). Managing Gorse as an Exclusion pest has a projected net benefit to the region of $157,369,811. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Gorse as a Control pest has a projected net benefit to the region of $130,199,994. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Gorse as an Advisory pest has a projected net benefit to the region of $188,483,926. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Gorse, Advisory, therefore meets the requirements of Sec- tion 72(1a) of the Act.

79 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 55,770 0.4 Potential extent (ha): 173,453

(57,885−−289,022) Proportion extent of maximum 0.2 Time to potential (yr): 25

Current prop. of potential: 0.578 0.0

−20 −10 0 10 20

Years from present

Figure 2.27: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

80 Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory control

● ● 1.0 ● ● 1.5 ● ● ● ● 5 ● ● 1.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.8 1.0 ●

● 4 ● 1.0 ● 0.8 0.6

3 0.6 0.4 0.4 0.5 Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area 2 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.2 ● ● ● ● ● ● 1 ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 81

1.0 ● 1.0 ● 1.0 ● 5

● Discount rate: 0.08 ● ● ● ● ● ● ● Total multiplier: 19.99 0.8 ● 0.8 0.8 4 ● ● (14−−49) ● ● ● ● 0.6 0.6 ● 0.6 3 ● ●

● ●

● ● ● ● ● 2 0.4 0.4 ● 0.4 ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.2 0.2 ● 0.2 1 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.28: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.16 Green goddess lily (Zantedeschia aethiopica “Green goddess”)

Proposed RPMS Category: Control Overall impact: Moderate

Table 2.118: Relevant biology

Attribute Description Form Robust, persistent, evergreen, clump-forming perennial herb ¡1.5m tall. Large arrow-shaped shiny green leaves. White, erect, funnel-shaped ‘ﬂower’ (Aug-Jan, occasionally other times of year) of central yellow spike and white outer modiﬁed leaf. Habitat Heavily disturbed shrubland and forest, damp areas with low cover, regenerating ex-pasture. Regional distribution Common in Tauranga district. Competitive ability Long-lived, smothers ground in open sites on most soil types. Persists under regenerating canopy. Drought-resistant once established. Forms dense patches excluding other plants. Poisonous, avoided by livestock, dominates grazed sites. Reproductive ability Produces viable seed. Dispersal methods Water, also planted by humans. Resistance to control Digging often leaves root fragments and dropped tuber pieces which resprout. Regrows after mowing.

Table 2.119: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity M H Forms dense patches in wetlands, smoth- 1 ers ground and excludes other species, preventing regeneration. Threatened species L M 1 Soil resources - L Potentially will impact on hydrology. 2 Water quality - - Production L M Poisonous (foliage avoided by livestock). 1, 3 International trade - - Human health M H Highly poisonous, causes shock, convul- 3, 4 sions, death. Recreation - - M¯aoriculture - L Unsightly, poisonous plant near water- 1 ways and cultural sites. Source: 1: Auckland Regional Council (2010a), 2: Stahl (2009), 3: Roy et al. (2004), 4: Environment Bay of Plenty (2004b)

82 Green goddess lily CBA results

Table 2.120: Green goddess lily CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 1,258,010 0 0 -1,258,010 (350,146–5,734,094) (-350,146 – -5,734,094) Exclusion Pest 646 1,257,364 3,373,319 -2,115,955 (195–1,018) (349,951–5,733,076) (-3,023,368 – 2,359,757) Control Pest 1,710 1,256,300 132,122 1,124,178 (491–2,853) (349,655–5,731,241) (217,533 – 5,599,119) Advisory Pest 872 1,257,138 13,212 1,243,926 (221–1,639) (349,925–5,732,455) (336,713 – 5,719,243)

Table 2.121: Green goddess lily CBA base assumptions.

Base assumptions Values Current area infested (ha) 20 Total area potentially infested (ha) 103,837 (35,106–172,567) Years from naturalisation to total area 75 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 7.59 (2.11–13.06) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.122: Green goddess lily RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 2.5 (0–5)

Table 2.123: Green goddess lily RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 12 (10–15)

Table 2.124: Green goddess lily RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5

83 Final area infested (ha) 30 (35–25)

Table 2.125: Green goddess lily estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 500,000 10,000 1,000

Green goddess lily conclusions

In the absence of regional control, the projected total regional damage in net present value is -$1,258,010 over the next 50 years (the minimum projected impact is -$350,146). Managing Green goddess lily as an Exclusion pest has a projected net benefit to the region of -$2,115,955. Since this is negative, this means that this management scenario does not meets the requirements of Section 72(1a) of the Act. Managing Green goddess lily as a Control pest has a projected net benefit to the region of $1,124,178. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Green goddess lily as an Advisory pest has a projected net benefit to the region of $1,243,926. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Green goddess lily, Control, therefore meets the requirements of Section 72(1a) of the Act.

84 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 20 0.4 Potential extent (ha): 103,837

(35,106−−172,567) Proportion extent of maximum 0.2 Time to potential (yr): 75

Current prop. of potential: <0.01 0.0

0 20 40 60

Years from present

Figure 2.29: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

85 Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory control

8000 ● ● ● 1.0 1.0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 1.5 ● ● ● ● ● ● ● ● 0.8 0.8 ● ● ● ● ● ● ● ● 6000 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.6 ● 0.6 1.0 ● 4000 ●

0.4 ● 0.4

● ● ● ● ● ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● 0.5 ● 2000 ● ● ● ● ● 0.2 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 86

8000 1.0 ● 1.0 ● 1.0 ● ● ● ● ● ● Discount rate: 0.08

● Total multiplier: 1958.79 0.8 0.8 0.8 ● ● 6000 (1190−−5792) ● ● ● 0.6 0.6 ● 0.6 ●

● 4000 ● ●

● ● 0.4 0.4 ● 0.4 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● 2000 ● ● ● ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.30: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.17 Hornwort (Ceratophyllum demersum)

Proposed RPMS Category: Control (deﬁned lakes) Overall impact: Major

Table 2.126: Relevant biology

Attribute Description Form Submerged, free-ﬂoating or anchored perennial in water to 16 m deep. No roots, usually lightly anchored by buried stems and leaves. Stems ﬂoating or submerged, branched, sti↵ and brittle, 30-150 cm long. Leaves in whorls of 7-12, densely crowded at stem apex and increasingly spaced down stem, thin, 1-4 cm long, equally forked once or twice into sti↵ tapering segments with teeth on the outer edge, dark green. Flowers minute, green or white. Habitat Regional distribution Lakes Rotoehu, Rotoiti, Rotomahana, Rotorua, Tarawera and many other waterbodies. Competitive ability Will out-compete other lake weeds. Reproductive ability Grows easily from broken fragments. No fruit set in NZ. Dispersal methods Water, humans. Resistance to control Dicult to control.

Table 2.127: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity H H Forms dense tall masses in freshwater (to 1, 2, 3 10 m deep), shades out smaller native species, prevents recruitment. Rotting vegetation deoxygenates water, killing fauna and ﬂora. Threatened species L H 1, 2 Soil resources - - Water quality M H Large clumps dislodge, causing blockage 1, 3 and ﬂooding. Rotting vegetation degrades water quality. Causes nutrient release from sediments, exacerbates eutrophica- tion. Production - - 1 International trade - - Human health - L Large weed beds may support more snails 4 which host the waterborne schistosome cercariae larvae that cause ’swimmers itch’. Recreation M H Dense masses block up lakes and shade 1, 2, 3 water, reducing access to lakes. Inconve- nience caused by biosecurity measures i.e. restricted access to lakes by lake cordons, cleaning and washing procedures. M¯aoriculture M H See Recreation. 1, 2, 3 Source: 1: Craw (2000), 2: Roy et al. (2004), 3: Clayton & Champion (2003), 4: NIWA (2002)

87 Hornwort CBA results

Since Hornwort is currently absent from the defined area, it is dicult to accurately quantify the costs and benefits of current and proposed e↵orts to continue to exclude the species. If the species were to invade this year and spread in the defined area, without regional control for the next 50 years, the total pest impacts over this period in net present value are calculated to be $163,994 ($109,329–$218,659). This can be compared with the calculated net present value of the proposed annual expenditure on control over this same period of $981,146 (to exclude the Control pest from the defined areas). Note that this comparison does not take into account whether or not the proposed level of expenditure is adequate to have a high probability of excluding the species over this period. Given the broad experience of the biosecurity sta↵ at Environment Bay of Plenty, we assume that it will be. The following tables provide the parameters used in this cost-benefit analysis.

Table 2.128: Hornwort CBA base assumptions.

Base assumptions Values Current area infested (ha) 0.25 Total area potentially infested (ha) 1,441 (1,441–1,441) Years from naturalisation to total area 25 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 18.75 (12.5–25) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.129: Hornwort estimated total annual cost of the proposed RPMS scenario (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Year Total Costs 1.00 74,261

Hornwort conclusions

Since the calculated average impact should the species invade is lower than the anticipated expenditure on regional surveillance and control, this management scenario fails meets the requirements of Section 72(1a) of the Act. The assessment of impacts in cost-benefit analyses for non-production pests is inherently dicult and if the Council decides that the value of keeping Hornwort from the defined area is worth more than $163,994 over the next 50 years, then this would satisfy the requirements of Section 72(1a) the Act. While the projected impacts are worth less than the proposed control for hornwort in ourCBA result, hornwort is a well recognised and clearly damaging lake weed and we are skeptical that the proposed costs would not be justified if the economic values of hornwort impacts on tourism, recreation, and biodiversity were more carefully quantified. If the Council concludes that it is worth more than $74,261 to the region to keep hornwort out of lakes Okareka, Okaro, Okataina, Rerewhakaaitu, Rotokakahi, Rotoma, and Tikitapu, then this satisfied section 72(1a) of the Act. As with all of the lake weeds that are in some region’s lakes and not others, if money is going to be spent trying to prevent hornwort’s movement into more lakes, a sucient amount needs to be spent to have a good chance of success. Otherwise, all the will be achieved is delaying the arrival of the weed into a lake by perhaps a few years.

88 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 0.25 0.4 Potential extent (ha): 1,441

Time to potential (yr): 25 Proportion extent of maximum 0.2 Current prop. of potential: <0.01

0.0

0 5 10 15 20 25

Years from present

Figure 2.31: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

89 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

●

● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 1.0 1.0 ● ● 1.0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 1500 ● ● ● ● ● ● 0.8 0.8 ● ● 0.8 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.6 ● 0.6 0.6 ● 1000 ●

● 0.4 ● 0.4 0.4

● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area 500

●

● 0.2 0.2 0.2

● ●

● ● ● ● 0 ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 90

1.0 ● 1.0 ● 1.0 ●

Discount rate: 0.08 ● ● ● ● 1500 ● Total multiplier: 8746.34 0.8 0.8 0.8 ● ● ●

(8746−−8746) ● ● ● 0.6 0.6 ● 0.6 1000 ● ● ●

●

● ● 0.4 0.4 ● 0.4 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● 500 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.32: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.18 Horse nettle (Solanum carolinense)

Proposed RPMS Category: Exclusion Overall impact: Moderate

Table 2.130: Relevant biology

Attribute Description Form Small shrub, grows to 1m. Leaves are alternate, elliptic-oblong to oval, irregularly lobed or coarsely toothed. Both surfaces are covered with ﬁne hairs. Flowers have ﬁve petals and are usually white or purple with yellow centers. Fruits resemble tomatoes, immature fruit is dark green with light green stripes, turning yellow and wrinkled as it matures. Habitat Pastures, roadsides, railroad margins, and in disturbed areas and waste ground. Prefers sandy or loamy soils. Regional distribution Te Puna and Cape Runaway. Competitive ability Reproductive ability Produces viable seed. Each fruit contains around 60 seeds. Dispersal methods Birds disperse seeds. Resistance to control Resistant to many herbicides, in fact herbicide use often selects for hors- enettle by removing competing weeds. The deep root makes it dicult to remove.

Table 2.131: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity - - 1, 2, 3 Threatened species - - 1, 2, 3 Soil resources - - 1, 2, 3 Water quality - - 1, 2, 3 Production M H Highly toxic to stock. 1, 2, 3 International trade L L Crop contaminant, prohibited seed (nil 4, 5, 6 tolerance) in imports into Australia. Human health L-M M Very dense and dicult to walk through. 1, 2, 3 Spines penetrate the skin and break o↵ when the plant is grasped. All parts of the plant are poisonous, and contain the toxic agent glycoalkaloid which causes depres- sion, excess salivation, diarrhoea, trem- bling, weakness and colic. Recreation L M See Human Health. 1, 2, 3 M¯aoriculture - M Obstructs access to cultural sites (e.g. 1, 2 waahi tapu, urupa). Source: 1: Anon. (2009e), 2: Anon. (2009a), 3: Anon. (2009d), 4: Senior (2009), 5: Stahl (2009), 6: Anon. (2009k)

91 Horse nettle CBA results

Table 2.132: Horse nettle CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 47,667,755 0 0 -47,667,755 (18,677,500–187,630,357) (-18,677,500 – -187,630,357) Exclusion Pest 17,368 47,650,387 114,693 47,535,694 (6,155–27,538) (18,671,345–187,602,819) (18,556,652 – 187,488,126) Control Pest 34,672 47,633,083 39,636 47,593,447 (11,427–59,187) (18,666,073–187,571,170) (18,626,437 – 187,531,534) Advisory Pest 15,722 47,652,033 13,212 47,638,821 (4,842–28,505) (18,672,658–187,601,852) (18,659,446 – 187,588,640)

Table 2.133: Horse nettle CBA base assumptions.

Base assumptions Values Current area infested (ha) 5 Total area potentially infested (ha) 50,755 (17,417–84,094) Years from naturalisation to total area 50 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 546.93 (185.4–908.46) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.134: Horse nettle RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 4.2 (3.8–4.8)

Table 2.135: Horse nettle RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 6 (6–5)

Table 2.136: Horse nettle RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 8 (9–6)

92 Table 2.137: Horse nettle estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 17,000 3,000 1,000

Horse nettle conclusions

In the absence of regional control, the projected total regional damage in net present value is -$47,667,755 over the next 50 years (the minimum projected impact is -$18,677,500). Managing Horse nettle as an Exclusion pest has a projected net benefit to the region of $47,535,694. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Horse nettle as a Control pest has a projected net benefit to the region of $47,593,447. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Horse nettle as an Advisory pest has a projected net benefit to the region of $47,638,821. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Horse nettle, Exclusion, therefore meets the requirements of Section 72(1a) of the Act.

93 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 5 0.4 Potential extent (ha): 50,755

(17,417−−84,094) Proportion extent of maximum 0.2 Time to potential (yr): 50

Current prop. of potential: <0.01 0.0

0 10 20 30 40 50

Years from present

Figure 2.33: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

94 Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory control

● 1.0 ● ● ● 1.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 15000 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 1.5 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.8 1.0 ● ● ● ● ● ●

●

0.8 ● 10000 0.6 1.0 ●

0.6 0.4

● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.4 ● 5000 ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● 0.5 ● ● ● 0.2 ● ● 0.2 ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 95

1.0 ● 1.0 ● 1.0 ● ● ● ● ● ● 15000 Discount rate: 0.08 ● ● Total multiplier: 10679.15 0.8 0.8 ● 0.8 ● ●

● (6446−−31118) ●

● ●

● 10000 0.6 ● 0.6 0.6 ● ● ●

● ●

● ● ● ● 0.4 0.4 ● 0.4 ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual 5000 cost Discounted annual cost Discounted annual ● ● ● ● ● ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.34: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.19 Italian buckthorn (Rhamnus alaternus)

Proposed RPMS Category: Control Overall impact: Moderate

Table 2.138: Relevant biology

Attribute Description Form Evergreen shrub growing up to 12 m tall. Habitat Coastal areas and bare rock. Also grows on margins of streams, scrub and forests. Regional distribution Coastal areas only. Competitive ability Grows equally well in shade or in the open, completely dominating many vegetation types. Will fruit under a closed canopy. Reproductive ability 90,000 to 180,000 seeds produced per individual. Separate male and female plants, which may account for its slow spread to date. Dispersal methods Birds, such as wax eyes, readily disperse the small fruit. Seeds have 80% viability. Resistance to control Can be controlled using herbicides and hand pulling young plants. Con- trol is dicult in many of the steep coastal sites. Beneﬁts Erosion control, holding up steep banks.

Table 2.139: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity M M Forms dense stands, dominates many veg- 1, 2, 3 etation types, prevents recruitment. Threatened species L M 1, 2, 3 Soil resources - - 4 Water quality - - 4 Production - L Excludes pasture species. 3 International trade - - 4 Human health - - 4 Recreation - - 4 M¯aoriculture L M Obstructs access to cultural sites (e.g. 4 waahi tapu, urupa). Source: 1: Craw (2000), 2: Ministry of Agriculture and Forestry (2008), 3: Anon. (2005a), 4: Severinsen (2003)

96 Italian buckthorn CBA results

Table 2.140: Italian buckthorn CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 2,218,273 0 0 -2,218,273 (316,160–11,629,410) (-316,160 – -11,629,410) Exclusion Pest 360 2,217,913 2,023,992 193,921 (134–545) (316,026–11,628,865) (-1,707,966 – 9,604,873) Control Pest 952 2,217,321 79,273 2,138,048 (337–1,527) (315,823–11,627,883) (236,550 – 11,548,610) Advisory Pest 441 2,217,832 13,212 2,204,620 (167–657) (315,993–11,628,753) (302,781 – 11,615,541)

Table 2.141: Italian buckthorn CBA base assumptions.

Base assumptions Values Current area infested (ha) 46 Total area potentially infested (ha) 142,406 (47,950–236,863) Years from naturalisation to total area 50 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 1.84 (0.63–3.04) Any beneﬁts provided by the weed 1 Discount rate 0.08

Table 2.142: Italian buckthorn RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 5.7 (0–11.5)

Table 2.143: Italian buckthorn RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 29 (23–34)

Table 2.144: Italian buckthorn RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5

97 Final area infested (ha) 58 (46–69)

Table 2.145: Italian buckthorn estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 300,000 6,000 1,000

Italian buckthorn conclusions

In the absence of regional control, the projected total regional damage in net present value is -$2,218,273 over the next 50 years (the minimum projected impact is -$316,160). Managing Italian buckthorn as an Exclusion pest has a projected net benefit to the region of $193,921. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Italian buckthorn as a Control pest has a projected net benefit to the region of $2,138,048. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Italian buckthorn as an Advisory pest has a projected net benefit to the region of $2,204,620. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Italian buckthorn, Control, therefore meets the requirements of Section 72(1a) of the Act.

98 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 46 0.4 Potential extent (ha): 142,406

(47,950−−236,863) Proportion extent of maximum 0.2 Time to potential (yr): 50

Current prop. of potential: 0.001 0.0

0 10 20 30 40 50

Years from present

Figure 2.35: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

99 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

●

● ● ● 1.0 1.0 ● ● 1.0 ● ● 5000 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.8 0.8 ● ● 0.8 4000 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 3000 0.6 0.6 0.6

●

● 2000 0.4 0.4 0.4

● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● ● ● ● ● ● 0.2 0.2 0.2 1000 ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 100

1.0 ● 1.0 ● 1.0 ● 5000

Discount rate: 0.08 ● ● ● ● ● Total multiplier: 3231.05 0.8 0.8 0.8 ● 4000 ● ● (2117−−9528) ● ● ● ● 3000 0.6 0.6 0.6 ●

● ●

●

● ● 0.4 0.4 ● 0.4 2000 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● ● ● 1000 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.36: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.20 Kudzu vine (Pueraria montana var.lobata)

Proposed RPMS Category: Exclusion Overall impact: Major

Table 2.146: Relevant biology

Attribute Description Form High climbing vine, often completely covering trees. Stems may reach up to 10 cm in diameter. Leaves alternate, compound 12-20 cm long, 3 individual leaflets 7-10 cm long, oval or may be lobed and fuzzy. Flower, large hanging clusters of pea like, purple to red flowers. Habitat Open distribution areas, roadsides, forest margins. Regional distribution Three known sites are Pahoia, Te Puke, Matata. Competitive ability Rapid growth will out compete all other plants. Reproductive ability No evidence of viable seed being produced. Dispersal methods Spreads by sending down roots from nearly every node along stems that contact soil and new crowns develop at these nodes. Resistance to control Dicult to control because of the large tubers. Benefits Used for erosion control, edible tubers, livestock feed, medicinal uses, making soap, lotions

Table 2.147: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity L H High climbing vine, forms dense patches 1, 2, 3 and smothers all other plants. Threatened species - H 1, 2, 3 Soil resources - - 1, 2, 3 Water quality - - 3 Production - M Smothers trees in plantation forests and 2, 3 orchards. Prevents access and creates safety hazard during harvest of plantation trees. International trade - - 3, 4 Human health - - 4 Recreation - M Dense walls of vines obstruct access to for- 2, 3 est. M¯aoriculture - M See Recreation. 2, 3 Source: 1: Anon. (2009c), 2: USDA (2005), 3: Anon. (2009i), 4: Severinsen (2003)

101 Kudzu vine CBA results

Table 2.148: Kudzu vine CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 4,042,904 0 0 -4,042,904 (895,728–19,589,206) (-895,728 – -19,589,206) Exclusion Pest 3 4,042,901 10,120 4,032,781 (1–5) (895,727–19,589,201) (885,607 – 19,579,081) Control Pest 8 4,042,896 13,212 4,029,684 (2–14) (895,726–19,589,192) (882,514 – 19,575,980) Advisory Pest 4 4,042,900 6,606 4,036,294 (1–6) (895,727–19,589,200) (889,121 – 19,582,594)

Table 2.149: Kudzu vine CBA base assumptions.

Base assumptions Values Current area infested (ha) 1.5 Total area potentially infested (ha) 142,235 (47,892–236,577) Years from naturalisation to total area 75 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 0.1 (0.1–0.9) Any beneﬁts provided by the weed 1 Discount rate 0.08

Table 2.150: Kudzu vine RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 0 (0–0.1)

Table 2.151: Kudzu vine RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 1 (0–1)

Table 2.152: Kudzu vine RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 2 (2–2)

102 Table 2.153: Kudzu vine estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 1,500 1,000 500

Kudzu vine conclusions

In the absence of regional control, the projected total regional damage in net present value is -$4,042,904 over the next 50 years (the minimum projected impact is -$895,728). Managing Kudzu vine as an Exclusion pest has a projected net benefit to the region of $4,032,781. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Kudzu vine as a Control pest has a projected net benefit to the region of $4,029,684. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Kudzu vine as an Advisory pest has a projected net benefit to the region of $4,036,294. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Kudzu vine, Exclusion, therefore meets the requirements of Section 72(1a) of the Act.

103 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 1.5 0.4 Potential extent (ha): 142,235

(47,892−−236,577) Proportion extent of maximum 0.2 Time to potential (yr): 75

Current prop. of potential: <0.01 0.0

0 20 40 60

Years from present

Figure 2.37: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

104 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

● 150000 ● ● ● ● 1.0 1.0 ● 1.0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.8 ● 0.8 ● 0.8 ● ● ● ● ● ● ● ● ● 100000 ● ● ● ● ● ● ● 0.6 0.6 ● 0.6 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.4 0.4 ● 0.4 ● ● 50000 ● ● ● ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● ● ● ● ● ● ● 0.2 0.2 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 105 150000 1.0 ● 1.0 ● 1.0 ●

Discount rate: 0.08 ● ● ● ● ● Total multiplier: 35641.61 0.8 0.8 0.8 ● ● ●

● 100000 (21429−−105849) ● ● 0.6 0.6 ● 0.6

●

● ●

●

● ● 0.4 0.4 ● 0.4 50000 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 ● ● 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.38: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.21 Lagarosiphon (Lagarosiphon major )

Proposed RPMS Category: Control (deﬁned lakes) Overall impact: Major

Table 2.154: Relevant biology

Attribute Description Form Submerged, bottom-rooting perennial, reaching to 5 m. Leaves recurved backwards or downwards, arranged spirally around the stem. Leaves 16 x 2 mm, with minute marginal serrations. Flowers tiny, pinkish. Habitat Rivers, lakes, dunelakes and other still or slow-moving waterbodies with mod-high light. Regional distribution Lakes Okareka, Okataina, Rerewhakaaitu, Rotoehu, Rotoiti, Rotoma, Rotorua, Tarawera, Tikitapu and many other waterbodies. Competitive ability Reproductive ability Grows easily from broken fragments. Only female plants found in NZ, no seed set. Dispersal methods Water, humans. Resistance to control Dicult to control.

Table 2.155: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity M H Forms vast deep meadows in freshwater 1, 2, 3, up to 4 m tall (to 6 m deep), shades out 4 smaller native species. Rotting vegetation deoxygenates water, killing fauna and ﬂora. Threatened species L H Serious threat to dune lakes and native 1, 2, 3 aquatic species. Soil resources - - Water quality M H Large clumps dislodge, causing blockage 1, 3, 4 and ﬂooding. Rotting vegetation degrades water quality. Causes nutrient release from sediments, exacerbates eutrophica- tion. Production - - 1, 3, 5 International trade - - Human health - L Large weed beds may support more snails 6 which host the waterborne schistosome cercariae larvae that cause ’swimmers itch’. Recreation M H Dense masses block up lakes and shade 1, 2, 3, water, reducing access to lakes. Inconve- 4 nience caused by biosecurity measures i.e. restricted access to lakes by lake cordons, cleaning and washing procedures. M¯aoriculture M H See Recreation. 1, 2, 3, 4 Source: 1: Craw (2000), 2: Roy et al. (2004), 3: Anon. (2006c), 4: Clayton & Champion (2003), 5: Department of Conservation (2007), 6: NIWA (2002)

106 Lagarosiphon CBA results

Since Lagarosiphon is currently absent from the defined area, it is dicult to accurately quantify the costs and benefits of current and proposed e↵orts to continue to exclude the species. If the species were to invade this year and spread in the defined area, without regional control for the next 50 years, the total pest impacts over this period in net present value are calculated to be $412,940 ($539,742–$442,649). This can be compared with the calculated net present value of the proposed annual expenditure on control over this same period of $245,286 (to exclude the Control pest from the defined areas). Note that this comparison does not take into account whether or not the proposed level of expenditure is adequate to have a high probability of excluding the species over this period. Given the broad experience of the biosecurity sta↵ at Environment Bay of Plenty, we assume that it will be. The following tables provide the parameters used in this cost-benefit analysis.

Table 2.156: Lagarosiphon CBA base assumptions.

Base assumptions Values Current area infested (ha) 0 Total area potentially infested (ha) 147 (147–147) Years from naturalisation to total area 25 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 7.38 (2.5–12.25) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.157: Lagarosiphon estimated total annual cost of the proposed RPMS scenario (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Year Total Costs 1.00 18,565

Lagarosiphon conclusions

107 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 0 0.4 Potential extent (ha): 147

Time to potential (yr): 25 Proportion extent of maximum 0.2 Current prop. of potential: <0.01

0.0

0 5 10 15 20 25

Years from present

Figure 2.39: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

108 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

●

● 0.4 ● 0.4 0.4

● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area 500

●

● 0.2 0.2 0.2

● ●

● ● ● ● 0 ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 109

1.0 ● 1.0 ● 1.0 ●

Discount rate: 0.08 ● ● ● ● 1500 ● Total multiplier: 8746.34 0.8 0.8 0.8 ● ● ●

(8746−−8746) ● ● ● 0.6 0.6 ● 0.6 1000 ● ● ●

●

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.40: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.22 Lantana (Lantana camara var.aculeata)

Proposed RPMS Category: Control Overall impact: Moderate

Table 2.158: Relevant biology

Attribute Description Form Aromatic prickly herbaceous shrub growing to 3 m tall. Habitat Coastal scrubland, islands, cli↵s, foreshores, consolidated dunes, forest margins, grassland, wasteland, exotic plantations, gardens. Regional distribution Concentrations in urban areas (grown as an ornamental). Competitive ability Very competitive in disturbed, high light conditions, can tolerate wet and dry. Reproductive ability Proliﬁc seeders. Dispersal methods Spread by birds. Resistance to control Major weed of overseas crops. Can be controlled with herbicide, but these may a↵ect surrounding vegetation. Biocontrol options have been investigated overseas but to date these are not promising.

Table 2.159: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity L M Totally smothers and replaces all other 1, 2, 3 species on the ground, causing permanent loss of habitat. Threatened species L M 1 Soil resources - - 4 Water quality - - 4 Production L M Toxic to stock. 1, 2, 3 International trade - - 4 Human health L-M L Fruit are highly poisonous, causes vomit- 3, 5 ing, diarrhoea, abdominal pain, sensitivity to light, coma. Recreation - L Dense stands restrict access. 3 M¯aoriculture - L Could obstruct access to cultural sites in 3 coastal areas (e.g. waahi tapu, urupa). Source: 1: Craw (2000), 2: Environment Bay of Plenty (2004a), 3: Environment Bay of Plenty (2003), 4: Severinsen (2003), 5: Environment Bay of Plenty (2004b)

110 Lantana CBA results

Table 2.160: Lantana CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 1,087,538 0 0 -1,087,538 (238,849–5,336,487) (-238,849 – -5,336,487) Exclusion Pest 612 1,086,926 2,529,990 -1,443,064 (176–972) (238,673–5,335,515) (-2,291,317 – 2,805,525) Control Pest 1,621 1,085,917 99,091 986,826 (444–2,724) (238,405–5,333,763) (139,314 – 5,234,672) Advisory Pest 751 1,086,787 13,212 1,073,575 (219–1,172) (238,630–5,335,315) (225,418 – 5,322,103)

Table 2.161: Lantana CBA base assumptions.

Base assumptions Values Current area infested (ha) 30 Total area potentially infested (ha) 140,045 (47,144–232,946) Years from naturalisation to total area 100 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 4.79 (1.27–8.31) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.162: Lantana RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 3.8 (0–7.5)

Table 2.163: Lantana RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 19 (15–22)

Table 2.164: Lantana RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 38 (30–45)

111 Table 2.165: Lantana estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 375,000 7,500 1,000

Lantana conclusions

In the absence of regional control, the projected total regional damage in net present value is -$1,087,538 over the next 50 years (the minimum projected impact is -$238,849). Managing Lantana as an Exclusion pest has a projected net benefit to the region of -$1,443,064. Since this is negative, this means that this management scenario does not meets the requirements of Section 72(1a) of the Act. Managing Lantana as a Control pest has a projected net benefit to the region of $986,826. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Lantana as an Advisory pest has a projected net benefit to the region of $1,073,575. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Lantana, Control, therefore meets the requirements of Section 72(1a) of the Act.

112 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 30 0.4 Potential extent (ha): 140,045

(47,144−−232,946) Proportion extent of maximum 0.2 Time to potential (yr): 100

Current prop. of potential: <0.01 0.0

0 20 40 60 80 100

Years from present

Figure 2.41: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

113 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

● 4000 ● ● ● 1.0 1.0 ● ● 1.0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.8 0.8 ● ● 0.8 3000 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.6 ● 0.6 0.6

2000 ●

0.4 ● 0.4 0.4

● ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● 1000 ● ● ● ● 0.2 0.2 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 114 4000 1.0 ● 1.0 ● 1.0 ●

Discount rate: 0.08 ● ● ● ● ● Total multiplier: 596.33 0.8 0.8 0.8 ● 3000 ● ● (387−−1769) ● ● ● 0.6 0.6 ● 0.6 ● 2000 ● ● ●

● ● 0.4 0.4 ● 0.4 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● 1000 ● ● ● ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.42: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.23 Marshwort (Nymphoides geminata)

Proposed RPMS Category: Exclusion Overall impact: Moderate

Table 2.166: Relevant biology

Attribute Description Form Aquatic perennial with branched stolons up to 1 m long usually just below surface and rounded, ﬂoating leaves with V-shaped sinus. Habitat Still water of swamps to fast ﬂowing freshwater streams, lake margins and small ponds. Regional distribution Eradicated from Lake Okareka, Rotorua. Competitive ability Spreads quickly and out-competes native aquatic plants. Reproductive ability No viable seed produced in New Zealand. Dispersal methods Spreads by branched runners, if a leaf is broken o↵ a new plant will grow. Spread most commonly through accidental or purposeful human intervention. Resistance to control No known suitable herbicide, can be controlled with weed mat for aquatic plants.

Table 2.167: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity - M Spreads quickly, forms dense mats of float- 1, 2 ing leaves, out-competes native aquatic plants. deoxygenates water killing flora and fauna. Threatened species - L 1, 2, 3 Soil resources - - 1 Water quality - M Dense mats deoxygenate water. 1, 2 Production - - 3 International trade - - 3 Human health - - 3 Recreation - M Dense mats restrict access to waterways 1, 2 for fishing, swimming, kayaking etc. M¯aoriculture - M See Recreation. 1, 2 Source: 1: Anon. (2007c), 2: Clayton & Tanner (1985), 3: Severinsen (2003)

115 Marshwort CBA results

Since Marshwort is currently absent from the region, it is dicult to accurately quantify the costs and beneﬁts of current and proposed e↵orts to continue to exclude the species. If the species were to invade this year and spread in the region, without regional control for the next 50 years, the total pest impacts over this period in net present value are calculated to be $17,017 ($2,147–$46,010). This can be compared with the calculated net present value of the proposed annual expenditure on control over this same period of $6,747 (Exclusion pest). Note that this comparison does not take into account whether or not the proposed level of expenditure is adequate to have a high probability of excluding the species over this period. Given the broad experience of the biosecurity sta↵ at Environment Bay of Plenty, we assume that it will be. The following tables provide the parameters used in this cost-beneﬁt analysis.

Table 2.168: Marshwort CBA base assumptions.

Base assumptions Values Current area infested (ha) 0 Total area potentially infested (ha) 4,216 (1,405–7,027) Years from naturalisation to total area 100 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 1 (1–1) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.169: Marshwort estimated total annual cost of the proposed RPMS scenario (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Year Total Costs 1.00 1,000

Marshwort conclusions

Since the calculated average impact should the species invade is greater than the anticipated expenditure, and regional establishment is likely in the absence of regional surveillance and preparations for rapid response, this management scenario meets the requirements of Section 72(1a) of the Act.

116 2.1.24 Nassella tussock (Nassella trichotoma)

Proposed RPMS Category: Exclusion Overall impact: Major

Table 2.170: Relevant biology

Attribute Description Form Perennial tussock forming grass growing to a height of 50 cm with numerous drooping ﬁne, rough leaves overtopped by slender open seed heads. Habitat Open sites such as sunny dry pasture, stream margins, roadsides and wasteland. Tolerates a wide range of climates. Regional distribution Conﬁned to one site in Opotiki District. Competitive ability Can form a complete cover in pasture situations. Reproductive ability Can produce up to 100,000 seeds per plant. Seed can remain dormant in the soil for over 15 years. Dispersal methods Primarily by wind but also stock, machinery, water, hay and as a seed impurity. Resistance to control Dicult to control due to large, long-lived seed bank.

Table 2.171: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity - H Forms pure stands in low-growing plant 1, 2 communities, esp. in harsh sites, excludes other species. Threatened species - H 1, 2 Soil resources - - Water quality - - 3 Production - H Cannot be digested by livestock (forms in- 1, 2 digestible balls in the stomach). Seeds spoil the ﬂeece. International trade - L Crop contaminant, prohibited seed (nil 4 tolerance) in imports into Australia. Human health - - 3 Recreation - - 3 M¯aoriculture - - 3 Source: 1: Craw (2000), 2: Anon. (2004b), 3: Severinsen (2003), 4: Anon. (2009k)

117 Nassella tussock CBA results

Table 2.172: Nassella tussock CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 7,177,008 0 0 -7,177,008 (2,786,207–27,839,851) (-2,786,207 – -27,839,851) Exclusion Pest 4 7,177,004 6,747 7,170,257 (5–4) (2,786,202–27,839,847) (2,779,455 – 27,833,100) Control Pest 11 7,176,997 6,606 7,170,391 (12–11) (2,786,195–27,839,840) (2,779,589 – 27,833,234) Advisory Pest 5 7,177,003 6,606 7,170,397 (6–5) (2,786,201–27,839,846) (2,779,595 – 27,833,240)

Table 2.173: Nassella tussock CBA base assumptions.

Base assumptions Values Current area infested (ha) 2 Total area potentially infested (ha) 58,294 (20,433–96,155) Years from naturalisation to total area 75 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 1 (1–1) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.174: Nassella tussock RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 0.2 (0–0.5)

Table 2.175: Nassella tussock RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 1 (1–2)

Table 2.176: Nassella tussock RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5

118 Final area infested (ha) 2 (2–3)

Table 2.177: Nassella tussock estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 1,000 500 500

Nassella tussock conclusions

In the absence of regional control, the projected total regional damage in net present value is -$7,177,008 over the next 50 years (the minimum projected impact is -$2,786,207). Managing Nassella tussock as an Exclusion pest has a projected net benefit to the region of $7,170,257. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Nassella tussock as a Control pest has a projected net benefit to the region of $7,170,391. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Nassella tussock as an Advisory pest has a projected net benefit to the region of $7,170,397. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Nassella tussock, Exclusion, therefore meets the requirements of Section 72(1a) of the Act.

119 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 2 0.4 Potential extent (ha): 58,294

(20,433−−96,155) Proportion extent of maximum 0.2 Time to potential (yr): 75

Current prop. of potential: <0.01 0.0

0 20 40 60

Years from present

Figure 2.43: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

120 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

●

● ● ● 1.0 1.0 ● ● 1.0 ● ● ● ● ● ● ● ● ● ● ● ● ● 40000 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.8 0.8 ● ● 0.8 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 30000 ● ● ● ● ● ● 0.6 ● 0.6 0.6

● 20000 0.4 ● 0.4 0.4

● ● ● ● ● ● ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● ● ● 10000 ● ● ● ● 0.2 0.2 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 121

1.0 ● 1.0 ● 1.0 ●

40000 Discount rate: 0.08 ● ● ● ● ● Total multiplier: 11310.66 0.8 0.8 0.8 ● ● ●

(6857−−32267) ● 30000 ● ● 0.6 0.6 ● 0.6 ●

● ●

●

20000 ● ● 0.4 0.4 ● 0.4 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● ● 10000 ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.44: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.25 Noogoora bur (Xanthium strumarium)

Proposed RPMS Category: Exclusion Overall impact: Moderate

Table 2.178: Relevant biology

Attribute Description Form Erect, annual herb less than 1m high. Stems have purple blotches, covered in short, upward pointing hairs. Roughly textured, dark green leaves have minute bristles, hairs and prominent veins. Inconspicuous ﬂowers (Jan-Mar) clustered at ends of branches. Hard, brown, woody burs with numerous spikes and hooks each contain two seeds. Habitat Pasture, open areas, roadsides. Prefers warm conditions on disturbed and fertile soil. Regional distribution On cropping land near Te Puke. Competitive ability Highly competitive with an extensive root system and rapid growth rate. Can form dense patches in pastures and crops and exclude all other ground species. Reproductive ability Brown burs each contain two seeds. Dispersal methods Seed dispersed by clinging to wool, fur, clothing and machinery. Also in agricultural seeds and gravel. Air pockets on spines of burs aids dispersal by water. Resistance to control Mechanical control is e↵ective but plants must be treated before any burs are formed to ensure seeding is prevented. Otherwise control must continue for at least 6 years.

Table 2.179: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity - L 1 Threatened species - L 1 Soil resources - L Excludes other ground-cover plants and 1 may leave areas of soil exposed to erosion after it dies back in autumn. Water quality - - Production L H Foliage on young plants and seeds are 1, 2, 3, toxic to stock, particularly pigs and cat- 4 tle. Burs contaminate wool. Competes with pasture species and can carry fungal diseases capable of infecting horticultural plants. International trade - L Can contaminate wool and crops. 1, 3, 4, 5 Human health - M Prickly, poisonous, can cause allergic skin 1, 3, 5, reaction. Pollen may cause hay fever. 6 Recreation - L Has prickly spines, could restrict access in 1, 6 coastal areas. M¯aoriculture - L Could obstruct access to cultural sites in 1 coastal areas (e.g. waahi tapu, urupa). Source: 1: Anon. (2009g), 2: Anon. (2009k), 3: Anon. (2005c), 4: Auckland Regional Council (2009), 5: Anon. (2009m), 6: Fischer et al. (1988)

122 Noogoora bur CBA results

Table 2.180: Noogoora bur CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 13,252,108 0 0 -13,252,108 (5,538,609–44,018,779) (-5,538,609 – -44,018,779) Exclusion Pest 2,763 13,249,345 67,466 13,181,879 (600–4,553) (5,538,009–44,014,226) (5,470,543 – 43,946,760) Control Pest 7,315 13,244,793 39,636 13,205,157 (1,509–12,757) (5,537,100–44,006,022) (5,497,464 – 43,966,386) Advisory Pest 3,389 13,248,719 13,212 13,235,507 (746–5,486) (5,537,863–44,013,293) (5,524,651 – 44,000,081)

Table 2.181: Noogoora bur CBA base assumptions.

Base assumptions Values Current area infested (ha) 7 Total area potentially infested (ha) 10,724 (4,039–17,409) Years from naturalisation to total area 50 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 92.7 (18.54–166.86) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.182: Noogoora bur RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 0.9 (0–1.8)

Table 2.183: Noogoora bur RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 4 (3–5)

Table 2.184: Noogoora bur RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 9 (7–10)

123 Table 2.185: Noogoora bur estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 10,000 3,000 1,000

Noogoora bur conclusions

In the absence of regional control, the projected total regional damage in net present value is -$13,252,108 over the next 50 years (the minimum projected impact is -$5,538,609). Managing Noogoora bur as an Exclusion pest has a projected net benefit to the region of $13,181,879. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Noogoora bur as a Control pest has a projected net benefit to the region of $13,205,157. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Noogoora bur as an Advisory pest has a projected net benefit to the region of $13,235,507. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Noogoora bur, Exclusion, therefore meets the requirements of Section 72(1a) of the Act.

124 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 7 0.4 Potential extent (ha): 10,724

(4,039−−17,409) Proportion extent of maximum 0.2 Time to potential (yr): 50

Current prop. of potential: 0.001 0.0

0 10 20 30 40 50

Years from present

Figure 2.45: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

125 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

●

● ● ● 2500 1.0 1.0 ● ● 1.0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 2000 ● ● 0.8 0.8 ● ● 0.8 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 1500 0.6 ● 0.6 0.6

●

1000 0.4 ● 0.4 0.4 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● ● ● ● 500 ● 0.2 0.2 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 126

2500 1.0 ● 1.0 ● 1.0 ●

Discount rate: 0.08 ● ● ● ● ● 2000 Total multiplier: 1937.89 0.8 0.8 0.8 ● ● ●

(1303−−4602) ● ● ● 1500 0.6 0.6 ● 0.6 ●

● ●

●

● ● 1000 0.4 0.4 ● 0.4 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● ● ● 500 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.46: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.26 Old man’s beard (Clematis vitalba)

Proposed RPMS Category: Control Overall impact: Major

Table 2.186: Relevant biology

Attribute Description Form Deciduous woody vine which grows along the ground or over trees and shrubs. Proliﬁc white ﬂowers. Habitat Scrub, wasteland, among willows, forest remnants, hedgerows, roadsides, river banks, in gardens, disturbed native bush, shelter belts. Prefers well-drained soils. Regional distribution Rotorua and Opotiki area, isolated infestations in other areas. Competitive ability Rapid growth rate. Can completely shade out canopy species, preferring well-drained alluvial soil. Light-demanding in seedling stage. Reproductive ability Produces ¿10,000 seeds per sq m, which remain viable on the vine over winter. Seed has an awn that enables it to bury into the soil for germination. Germination rate ¿80%. Dispersal methods Usually spread by wind over short distances, or water over long distances, can also be spread in road gravel. Resistance to control Dicult to eradicate but mature vines can be treated by cut and paint techniques using clopyralid, glyphosate or metsulfuron. Use of herbicides compromised by plants’ climbing nature. Two biological control agents are available reducing plant vigour and killing seedlings.

Table 2.187: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity L H Forms dense, heavy, permanent masses. 1 Smothers and kills all plants to highest canopy, prevents recruitment. Threatened species - H 1 Soil resources - - 2 Water quality - - 2 Production L M Smothers trees in plantation forests and 2 orchards. Prevents access and creates safety hazard during harvest of plantation trees. International trade - - 2 Human health - - 2 Recreation - M Forms dense, heavy, permanent masses 1 which obstruct access to forest. M¯aoriculture L M See Recreation. 1 Source: 1: Craw (2000), 2: Severinsen (2003)

127 Old man’s beard CBA results

Table 2.188: Old man’s beard CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 472,264 0 0 -472,264 (129,825–1,352,364) (-129,825 – -1,352,364) Exclusion Pest 1,524 470,740 7,252,637 -6,781,897 (386–2,464) (129,439–1,349,900) (-7,123,198 – -5,902,737) Control Pest 4,034 468,230 284,062 184,168 (971–6,905) (128,854–1,345,459) (-155,208 – 1,061,397) Advisory Pest 2,152 470,112 13,212 456,900 (480–3,968) (129,345–1,348,396) (116,133 – 1,335,184)

Table 2.189: Old man’s beard CBA base assumptions.

Base assumptions Values Current area infested (ha) 120 Total area potentially infested (ha) 135,022 (45,007–225,037) Years from naturalisation to total area 125 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 2.98 (0.7–5.27) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.190: Old man’s beard RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 15 (0–30)

Table 2.191: Old man’s beard RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 75 (60–90)

Table 2.192: Old man’s beard RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5

128 Final area infested (ha) 195 (210–180)

Table 2.193: Old man’s beard estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 1,075,000 21,500 1,000

Old man’s beard conclusions

In the absence of regional control, the projected total regional damage in net present value is -$472,264 over the next 50 years (the minimum projected impact is -$129,825). Managing Old man’s beard as an Exclusion pest has a projected net benefit to the region of - $6,781,897. Since this is negative, this means that this management scenario does not meets the requirements of Section 72(1a) of the Act. Managing Old man’s beard as a Control pest has a projected net benefit to the region of $184,168. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Old man’s beard as an Advisory pest has a projected net benefit to the region of $456,900. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Old man’s beard, Control, therefore meets the requirements of Section 72(1a) of the Act.

129 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 120 0.4 Potential extent (ha): 135,022

(45,007−−225,037) Proportion extent of maximum 0.2 Time to potential (yr): 125

Current prop. of potential: 0.002 0.0

0 20 40 60 80 100 120

Years from present

Figure 2.47: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

130 Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory control

350 ● ● 1.0 1.0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 300 ● ● ● ● ● 1.5 ● ● ● ● ● ● ● ● ● 0.8 0.8 ● ● ● ● ● ● ● ● 250 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.6 ● 0.6 200 1.0 ● ● ● ●

●

150 ● ● ● 0.4 0.4 ● ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area 100 ● 0.5 ● ● ● ● ● 0.2 0.2 ● ● 50 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 131

● ● 350 ● 1.0 ● 1.0 ● 1.0 ● ● ●

Discount rate: 0.08 300 ● Total multiplier: 123.27 0.8 0.8 0.8 ● ●

250 ● (105−−176) ● ● ● 200 0.6 0.6 0.6 ●

● ●

●

● 150 ● 0.4 0.4 ● 0.4 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual 100 cost Discounted annual cost Discounted annual ● ● ● ● ● ● 0.2 0.2 ● 0.2 ● ● ● ● 50 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.48: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.27 Pampas (Cortaderia selloana, C. jubata and cultivars)

Proposed RPMS Category: Advisory Overall impact: Moderate

Table 2.194: Relevant biology

Attribute Description Form A tall tussock grass (to 4 m tall) with sharp leaves mostly developing from the base. Purple pampas has a large purple plume whereas in common pampas the flower plume is yellow. Habitat Distributed from subtropical to temperate regions. Prefers disturbed areas like roadside banks, slip faces, and river banks. Common in forestry blocks. Regional distribution Widespread across region. Competitive ability A major problem in forestry areas. The root system of a single plant can occupy as much as 103 cubic m of soil. Reproductive ability Up to 100,000 seeds can be produced per flower head. Dispersal methods Seed dispersed primarily by wind (reputedly 10-25 km) however, gravel, vehicles and animals can also carry seed. Resistance to control Can be controlled using herbicides but is dicult and repeat applications are often necessary. Size of mature plants makes mechanical removal dicult. Sometimes grazed by stock. Benefits Used as hedges, windbreaks on farms

Table 2.195: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity M H Colonises sprayed, burnt, disturbed sites 1 and quickly becomes very dense. Replaces native ground covers, shrubs, ferns. Pro- vides habitat for possums and rats. Threatened species L M 1 Soil resources - - 2 Water quality - - 2 Production M M Problem in young plantation forests, 1 quickly becomes very dense. Build-up of dead leaves, leaf bases and flowering stalks creates a significant fire hazard. International trade L M Seed can contaminate kiwifruit and lead 3 to entire crop being rejected for export. Human health L L Sharp leaves can cut skin. 4 Recreation M M Forms dense patches which restrict access. 1 M¯aoriculture M M See Recreation. 1 Source: 1: Craw (2000), 2: Severinsen (2003), 3: Mather (2009), 4: Department of Conservation (1997a)

132 Pampas CBA results

Table 2.196: Pampas CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 53,984,513 0 0 -53,984,513 (13,745,734–171,093,381) (-13,745,734 – -171,093,381) Exclusion Pest 3,742,891 50,241,622 236,132,363 -185,890,741 (1,375,703–5,690,778) (12,370,031–165,402,603) (-223,762,332 – -70,729,760) Control Pest 9,907,746 44,076,767 13,212,163 30,864,604 (3,461,847–15,945,199) (10,283,887–155,148,182) (-2,928,276 – 141,936,019) Advisory Pest 4,590,574 49,393,939 66,061 49,327,878 (1,712,186–6,857,469) (12,033,548–164,235,912) (11,967,487 – 164,169,851)

Table 2.197: Pampas CBA base assumptions.

Base assumptions Values Current area infested (ha) 6,000 Total area potentially infested (ha) 178,639 (59,558–297,720) Years from naturalisation to total area 75 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 146.48 (49.63–243.33) Any beneﬁts provided by the weed 1 Discount rate 0.08

Table 2.198: Pampas RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 750 (0–1,500)

Table 2.199: Pampas RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 3,750 (3,000–4,500)

Table 2.200: Pampas RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 7,500 (6,000–9,000)

133 Table 2.201: Pampas estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 35,000,000 1,000,000 5,000

Pampas conclusions

In the absence of regional control, the projected total regional damage in net present value is -$53,984,513 over the next 50 years (the minimum projected impact is -$13,745,734). Managing Pampas as an Exclusion pest has a projected net benefit to the region of -$185,890,741. Since this is negative, this means that this management scenario does not meets the requirements of Section 72(1a) of the Act. Managing Pampas as a Control pest has a projected net benefit to the region of $30,864,604. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Pampas as an Advisory pest has a projected net benefit to the region of $49,327,878. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Pampas, Advisory, therefore meets the requirements of Section 72(1a) of the Act.

134 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 6,000 0.4 Potential extent (ha): 178,639

(59,558−−297,720) Proportion extent of maximum 0.2 Time to potential (yr): 75

Current prop. of potential: 0.06 0.0

−20 0 20 40 60

Years from present

Figure 2.49: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

135 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ● 50 ● ● ● ● 1.0 1.0 ● ● 1.0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 40 ● ● ● ● ● 0.8 0.8 ● ● 0.8 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 30 0.6 ● 0.6 0.6

●

20 0.4 ● 0.4 0.4

● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● ● ● ● ● ● ● ● ● ● ● ● 0.2 0.2 0.2 10 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 136 50 1.0 ● 1.0 ● 1.0 ●

Discount rate: 0.08 ● ● ● ● 40 ● Total multiplier: 61.33 0.8 0.8 0.8 ● ● ●

(46−−117) ● ● ● 30 0.6 0.6 ● 0.6 ●

● ●

●

● ● 20 0.4 0.4 ● 0.4 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● ● ● 10 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 ● ● ● ● 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.50: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.28 Privet (Ligustrum lucidum, L. sinense)

Proposed RPMS Category: Advisory Overall impact: Moderate

Table 2.202: Relevant biology

Attribute Description Form Medium sized evergreen tree growing up to 10 m tall (tree privet). Ev- ergreen or semi-deciduous shrub as small tree up to 5 m tall (Chinese privet). Habitat Widely grown as hedging plant, also occurs in lowland and coastal forest, mostly remnants and shrub land. Urban areas, disturbed sites, roadside banks, waste areas. Regional distribution Widespread across region. Competitive ability Tree privet is shade tolerant and competitive on a wide range of soils. Chinese privet is also shade tolerant (probably also shade requiring). Fire intolerant. Reproductive ability Both species produce 100,000-10,000,000 seeds per bush or tree. Dispersal methods Seed dispersed by birds. Resistance to control Adequately controlled by cutting and painting with metsulfuron, but this can possibly damage surrounding areas.

Table 2.203: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity M H Dense stands prevent recruitment. Dis- 1, 2 places vulnerable shrub species. Poi- sonous berries may possibly impact on native fauna, esp. insects. Threatened species L L 1, 2 Soil resources - - 3 Water quality - - 3 Production L L Forms dense stands. 2, 4 International trade - - 3 Human health M M Berries and leaves are poisonous. There is 1, 2 no convincing evidence that pollen a↵ects asthma and hay fever although many people believe this. Recreation L L Forms dense stands which restrict access. 1, 2 M¯aoriculture L M See Recreation. 3 Source: 1: Craw (2000), 2: Environment Bay of Plenty (2005g), 3: Severinsen (2003), 4: Environment Bay of Plenty (2004a)

137 Privet CBA results

Table 2.204: Privet CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 6,055,811 0 0 -6,055,811 (1,405,216–25,388,392) (-1,405,216 – -25,388,392) Exclusion Pest 249,520 5,806,291 472,264,726 -466,458,435 (72,095–395,928) (1,333,121–24,992,464) (-470,931,605 – -447,272,262) Control Pest 660,500 5,395,311 13,212,163 -7,816,852 (181,422–1,109,364) (1,223,794–24,279,028) (-11,988,369 – 11,066,865) Advisory Pest 306,031 5,749,780 132,122 5,617,658 (89,729–477,098) (1,315,487–24,911,294) (1,183,365 – 24,779,172)

Table 2.205: Privet CBA base assumptions.

Base assumptions Values Current area infested (ha) 6,000 Total area potentially infested (ha) 106,584 (36,487–176,682) Years from naturalisation to total area 25 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 9.77 (2.6–16.93) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.206: Privet RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 750 (0–1,500)

Table 2.207: Privet RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 3,750 (3,000–4,500)

Table 2.208: Privet RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 7,500 (6,000–9,000)

138 Table 2.209: Privet estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 70,000,000 1,000,000 10,000

Privet conclusions

In the absence of regional control, the projected total regional damage in net present value is -$6,055,811 over the next 50 years (the minimum projected impact is -$1,405,216). Managing Privet as an Exclusion pest has a projected net benefit to the region of -$466,458,435. Since this is negative, this means that this management scenario does not meets the requirements of Section 72(1a) of the Act. Managing Privet as a Control pest has a projected net benefit to the region of -$7,816,852. Since this is negative, this means that this management scenario does not meet the requirements of Section 72(1a) of the Act. Managing Privet as an Advisory pest has a projected net benefit to the region of $5,617,658. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Privet, Advisory, therefore meets the requirements of Section 72(1a) of the Act.

139 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 6,000 0.4 Potential extent (ha): 106,584

(36,487−−176,682) Proportion extent of maximum 0.2 Time to potential (yr): 25

Current prop. of potential: 0.099 0.0

−10 0 10 20

Years from present

Figure 2.51: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

140 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

●

30 ● ● ● 1.0 1.0 ● ● 1.0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 25 ● ● ● ● ● ● ● 0.8 0.8 ● ● 0.8 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 20 ● ● ● ● ● ● 0.6 ● 0.6 0.6

● 15

0.4 ● 0.4 0.4

● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 10 ● ● ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● ● ● ● ● ● 0.2 0.2 0.2 ● 5 ● ● ● ● ● ● ● 0.0 0.0 0.0 0 0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 141 30 1.0 ● 1.0 ● 1.0 ●

Discount rate: 0.08 ● ● 25 ● ● ● Total multiplier: 84.7 0.8 0.8 0.8 ● ● ●

(55−−212) ● 20 ● ● 0.6 0.6 ● 0.6 ● 15 ● ● ●

● ● 0.4 0.4 ● 0.4 ● ● 10 ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● ● ● 0.2 0.2 ● 0.2 ● ● 5 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 ● ● ● ● 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.52: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.29 Ragwort (Senecio jacobaea)

Proposed RPMS Category: Advisory Overall impact: Moderate

Table 2.210: Relevant biology

Attribute Description Form An erect biennial or perennial herb, usually growing to 45-60 cm. Single or several stems arise from a crown, with dark green leaves. Flowers are bright yellow and clustered at the end of the branches. Habitat Waste places and pasture, also riverbeds, open forest, swamps. Occurs in humid temperate regions with annual rainfall greater than 750 mm. Tolerates frost. Regional distribution Widespread throughout region. Most problematic in dairying districts because of higher rainfall and unpalatable to cattle. Competitive ability Establishment is poor in pasture but good in disturbed soil. Early growth is slow and seedling mortality high. Reproductive ability Can flower all year around. A well developed plant may produce 250,000 seeds per year of which 80% may be viable. Seed can be viable for at least 8 years and germinate when brought to the surface. Dispersal methods Wind is main method of seed spread. New Zealand study showed bulk of seed fell to ground within 5 m of the parent plant and virtually none was blown more than 37 m. Resistance to control Can be controlled grazing, mowing, grubbing, and herbicides, but can become resistant to chemical control as a result of poor application. Grubbing and spraying can produce multi-headed plants. Plants may regenerate after flowering. Ragwort flea beetle is widespread throughout the region and appears to be achieving reasonable control.

Table 2.211: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity - - 1 Threatened species - - 1 Soil resources - - 1 Water quality - - 1 Production M M Forms dense stands in disturbed and 2, 3, 4, grazed areas. Alkaloids present are toxic 5 to horses, cattle, deer. International trade - L Prohibited seed of nil tolerance in Aus- 6 tralia. Human health L L Can cause skin irritation and allergies 7 when handed extensively. Recreation - - 1 M¯aoriculture - - 1 Source: 1: Severinsen (2003), 2: Craw (2000), 3: Roy et al. (2004), 4: Environment Bay of Plenty (2005h), 5: Anon. (2007e), 6: Anon. (2009k), 7: Gourlay (2009)

142 Ragwort CBA results

Table 2.212: Ragwort CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 5,752,613,251 0 0 -5,752,613,251 (3,031,907,182–3,524,596,474) (-3,031,907,182 – -3,524,596,474) Exclusion Pest 285,465,812 5,467,147,439 27,492,554 5,439,654,885 (99,830,471–438,326,138) (2,932,076,711–3,086,270,336) (2,904,584,157 – 3,058,777,782) Control Pest 755,651,959 4,996,961,292 1,076,791 4,995,884,501 (251,215,426–1,228,161,911) (2,780,691,756–2,296,434,563) (2,779,614,965 – 2,295,357,772) Advisory Pest 314,847,652 5,437,765,599 13,212 5,437,752,387 (101,506,066–528,189,237) (2,930,401,116–2,996,407,237) (2,930,387,904 – 2,996,394,025)

Table 2.213: Ragwort CBA base assumptions.

Base assumptions Values Current area infested (ha) 253,856 Total area potentially infested (ha) 62,322 (22,295–102,349) Years from naturalisation to total area 50 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 264.06 (85.13–442.98) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.214: Ragwort RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 31,732 (0–63,464)

Table 2.215: Ragwort RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 158,660 (126,928–190,392)

Table 2.216: Ragwort RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 253,856 (253,856–253,856)

143 Table 2.217: Ragwort estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 4,075,000 81,500 1,000

Ragwort conclusions

In the absence of regional control, the projected total regional damage in net present value is -$5,752,613,251 over the next 50 years (the minimum projected impact is -$3,031,907,182). Managing Ragwort as an Exclusion pest has a projected net benefit to the region of $5,439,654,885. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Ragwort as a Control pest has a projected net benefit to the region of $4,995,884,501. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Ragwort as an Advisory pest has a projected net benefit to the region of $5,437,752,387. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Ragwort, Advisory, therefore meets the requirements of Section 72(1a) of the Act.

144 Calibrated logistic growth curve 1.0 0.8 0.6

Current extent (ha): 253,856 0.4 Potential extent (ha): 62,322

(22,295−−102,349) Proportion extent of maximum 0.2 Time to potential (yr): 50

Current prop. of potential: 6.933 0.0

0 10 20 30 40 50

Years from present

Figure 2.53: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

145 Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory control

● 2.5 ● ● ● ● ● ● ● ● 1.0 1.0 ● ● 1.0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.8 0.8 ● ● 0.8 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 2.0 ● ● ● ● ● ● ● 0.6 ● 0.6 0.6

● ●

0.4 ● 0.4 0.4

● 1.5 ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area

● ● 0.2 0.2 0.2

●

1.0 ● 0.0 0.0 0.0 ● 0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5 ● Years from present Years from present Years from present Years from present ●

● Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control ● 146

● 2.5 1.0 ● 1.0 ● 1.0 ● ●

● Discount rate: 0.08 ● ● ● 2.0 Total multiplier: 85.82 0.8 0.8 0.8 ● ● ● ● ● ● ● (140−−31) ● ● ● ● ● 1.5 ● 0.6 0.6 ● 0.6 ● ●

● ● ●

● ●

● ● ● ● 1.0 ● ● ● 0.4 0.4 0.4 ● ● ● ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual ● cost Discounted annual cost Discounted annual ● ● ● ● ● ● ● ● ● ● 0.5 ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0 ● ● ● ● ● 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.54: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.30 Royal fern (Osmunda regalis)

Proposed RPMS Category: Control Overall impact: Major

Table 2.218: Relevant biology

Attribute Description Form Rhizomatous fern with thick erect trunks to 1.5 m tall. Fronds to 3 m long. Fertile fronds bearing sterile pinnae at the base and much reduced fertile pinnae at the tip of the frond. Habitat Wetlands. Regional distribution Matakana Island, Kaituna Wetland, Matata and Rotorua areas. Competitive ability Can exclude other wetland species. Reproductive ability Produces fertile spores. Dispersal methods Disperses by spores. Resistance to control Unknown.

Table 2.219: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity H H Competes with native species for space in 1, 2 specialised niches, one of very few weeds of bogs. Threatened species H H Impacting on rare ferns on Matakana Is- 1, 2 land (e.g., Cyclosorus sp.). Soil resources - - 3 Water quality - - 3 Production - - 3 International trade - - 3 Human health - - 3 Recreation - - 3 M¯aoriculture - L Could obstruct access to cultural sites 1 (e.g. waahi tapu, urupa). Source: 1: Craw (2000), 2: Stahl (2009), 3: Severinsen (2003)

147 Royal fern CBA results

Table 2.220: Royal fern CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 400,907 0 0 -400,907 (218,700–792,825) (-218,700 – -792,825) Exclusion Pest 31,940 368,967 4,216,649 -3,847,682 (23,097–38,978) (195,603–753,847) (-4,021,046 – -3,462,802) Control Pest 84,547 316,360 165,152 151,208 (58,122–109,215) (160,578–683,610) (-4,574 – 518,458) Advisory Pest 39,173 361,734 13,212 348,522 (28,746–46,970) (189,954–745,855) (176,742 – 732,643)

Table 2.221: Royal fern CBA base assumptions.

Base assumptions Values Current area infested (ha) 400 Total area potentially infested (ha) 19,237 (7,414–31,060) Years from naturalisation to total area 100 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 18.75 (12.5–25) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.222: Royal fern RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 50 (0–100)

Table 2.223: Royal fern RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 250 (200–300)

Table 2.224: Royal fern RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 500 (400–600)

148 Table 2.225: Royal fern estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 625,000 12,500 1,000

Royal fern conclusions

In the absence of regional control, the projected total regional damage in net present value is -$400,907 over the next 50 years (the minimum projected impact is -$218,700). Managing Royal fern as an Exclusion pest has a projected net benefit to the region of -$3,847,682. Since this is negative, this means that this management scenario does not meets the requirements of Section 72(1a) of the Act. Managing Royal fern as a Control pest has a projected net benefit to the region of $151,208. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Royal fern as an Advisory pest has a projected net benefit to the region of $348,522. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Royal fern, Control, therefore meets the requirements of Section 72(1a) of the Act.

149 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 400 0.4 Potential extent (ha): 19,237

(7,414−−31,060) Proportion extent of maximum 0.2 Time to potential (yr): 100

Current prop. of potential: 0.033 0.0

−40 −20 0 20 40 60 80 100

Years from present

Figure 2.55: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

150 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

●

● ● ● 1.0 1.0 ● ● 1.0 ● ● ● ● ● ● ● ● 60 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.8 0.8 ● ● 0.8 50 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 40 0.6 ● 0.6 0.6

● 30 ● ● ● ● ● ● 0.4 0.4 0.4 ● ● ● ● ● ● ● ● ● ● 20 ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● ● ● ● ● ● ● ● ● 0.2 0.2 0.2 ● ● ● ● 10 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 151

1.0 ● 1.0 ● 1.0 ● 60 Discount rate: 0.08 ● ● ● ● ● Total multiplier: 61.1 0.8 0.8 0.8 ● 50 ● ● (49−−95) ● ● ● 40 0.6 0.6 ● 0.6 ●

● ● 30 ● ● ● 0.4 0.4 ● 0.4 ● ● ● 20 ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● ● ● 0.2 0.2 ● 0.2 ● ● ● ● 10 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 ● ● ● ● ● 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.56: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.31 Saltwater paspalum (Paspalum vaginatum)

Proposed RPMS Category: Advisory Overall impact: Moderate

Table 2.226: Relevant biology

Attribute Description Form Perennial grass that forms dense mats along margins of tidal flats or on sandy or gravel beaches. Habitat Margins of estuaries and sandy and gravel beaches. Regional distribution Tauranga Harbour, Ohiwa Harbour and other estuaries in the region. Competitive ability Forms dense mats along margins of tidal flats or on sandy gravel beaches. Reproductive ability Does not set viable seed in NZ. Dispersal methods Spread by fragments floating in the water or by cattle grazing. Deliber- ately planted by humans for erosion control. Resistance to control Unknown. Benefits Prevents erosion in estuaries and along the coast.

Table 2.227: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity H H Forms dense mats along margins of tidal 1, 2 flats or on sandy gravel beaches. Reduces feeding and roosting sites for birds, may alter fish spawning and feeding grounds. Threatened species L H 1 Soil resources - - 1 Water quality L L May change estuarine hydrology by accu- 1 mulating sedliment. Production - - 1 International trade - - 1 Human health - - 1 Recreation L M Forms dense patches which restrict access 1 to estuaries. M¯aoriculture L M Could destroy and obstruct access to 1, 3 kaimoana (shellfish) gathering areas. Source: 1: QEII (2008), 2: Stahl (2009), 3: Hutchison (2009)

152 Saltwater paspalum CBA results

Table 2.228: Saltwater paspalum CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 21,693 0 0 -21,693 (11,466–47,526) (-11,466 – -47,526) Exclusion Pest 3,194 18,499 1,349,328 -1,330,829 (2,310–3,898) (9,156–43,628) (-1,340,172 – -1,305,700) Control Pest 8,929 12,764 264,243 -251,479 (6,093–11,624) (5,373–35,902) (-258,870 – -228,341) Advisory Pest 4,154 17,539 13,212 4,327 (2,401–6,275) (9,065–41,251) (-4,147 – 28,039)

Table 2.229: Saltwater paspalum CBA base assumptions.

Base assumptions Values Current area infested (ha) 100 Total area potentially infested (ha) 1,032 (344–1,720) Years from naturalisation to total area 100 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 7.5 (5–10) Any beneﬁts provided by the weed 1 Discount rate 0.08

Table 2.230: Saltwater paspalum RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 12.5 (0–25)

Table 2.231: Saltwater paspalum RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 85 (75–95)

Table 2.232: Saltwater paspalum RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5

153 Final area infested (ha) 140 (175–105)

Table 2.233: Saltwater paspalum estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 200,000 20,000 1,000

Saltwater paspalum conclusions

In the absence of regional control, the projected total regional damage in net present value is -$21,693 over the next 50 years (the minimum projected impact is -$11,466). Managing Saltwater paspalum as an Exclusion pest has a projected net benefit to the region of -$1,330,829. Since this is negative, this means that this management scenario does not meets the requirements of Section 72(1a) of the Act. Managing Saltwater paspalum as a Control pest has a projected net benefit to the region of - $251,479. Since this is negative, this means that this management scenario does not meet the requirements of Section 72(1a) of the Act. Managing Saltwater paspalum as an Advisory pest has a projected net benefit to the region of $4,327. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Saltwater paspalum, Advisory, therefore meets the requirements of Section 72(1a) of the Act.

154 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 100 0.4 Potential extent (ha): 1,032

(344−−1,720) Proportion extent of maximum 0.2 Time to potential (yr): 100

Current prop. of potential: 0.174 0.0

−50 0 50 100

Years from present

Figure 2.57: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

155 Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory control

● ● ● ● 1.0 1.0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 15 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 1.5 0.8 ● 0.8 ● ●

● ●

● 10 0.6 ● 0.6 ● 1.0 ●

●

0.4 ● 0.4

● ● ● ● ● ● ● ● ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● ● ● ● ● 0.5 5 ● ● ● ● ● ● ● ● ● ● ● ● ● 0.2 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 156

1.0 ● 1.0 ● 1.0 ● 15 ● ● ● ● Discount rate: 0.08 ● ●

Total multiplier: 28.92 0.8 0.8 ● 0.8 ●

● (23−−48) ● ● 10 ● 0.6 0.6 0.6 ●

● ● ●

● ● ● 0.4 0.4 ● 0.4 ● ● ● 5 ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● ● ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.58: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.32 Senegal tea (Gymnocoronis spilanthoides)

Proposed RPMS Category: Exclusion Overall impact: Major

Table 2.234: Relevant biology

Attribute Description Form Mat forming perennial aquatic herb with scrambling, floating stems, which produce roots at nodes. Stems erect when flowering to 1.5 m tall. Habitat Wet marshy soils often spreading out from water margins to form a floating mat. Regional distribution One site at Welcome Bay. Competitive ability Dominates shorter herbaceous vegetation and floating mats shade out submerged species. Reproductive ability Few seeds are produced in New Zealand, however seeds are highly fertile. Dispersal methods Spreads by stem fragmentation, humans and machinery. Seeds dispersed by water movement. Resistance to control Mechanical control unsuccessful as it spreads fragments of the plant. Can be controlled with herbicides.

Table 2.235: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity - H Dominates shorter vegetation and ﬂoating 1, 2, 3 mats shade out submerged species. Threatened species - H 1, 2, 3 Soil resources - - 4 Water quality - H Blocks up waterways. 1, 2, 3 Production - - 3 International trade - - 4 Human health - - 4 Recreation - M Dense mats restrict access to waterways 2, 3 for ﬁshing, swimming, kayaking etc. M¯aoriculture - M See Recreation. 5 Source: 1: Craw (2000), 2: Anon. (2007f), 3: Anon. (2009h), 4: Severinsen (2003), 5: Stahl (2009)

157 Senegal tea CBA results

Since Senegal tea is currently absent from the region, it is dicult to accurately quantify the costs and beneﬁts of current and proposed e↵orts to continue to exclude the species. If the species were to invade this year and spread in the region, without regional control for the next 50 years, the total pest impacts over this period in net present value are calculated to be $106,639 ($47,878– $188,615). This can be compared with the calculated net present value of the proposed annual expenditure on control over this same period of $6,747 (Exclusion pest). Note that this comparison does not take into account whether or not the proposed level of expenditure is adequate to have a high probability of excluding the species over this period. Given the broad experience of the biosecurity sta↵ at Environment Bay of Plenty, we assume that it will be. The following tables provide the parameters used in this cost-beneﬁt analysis.

Table 2.236: Senegal tea CBA base assumptions.

Table 2.237: Senegal tea estimated total annual cost of the proposed RPMS scenario (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Year Total Costs 1.00 1,000

Senegal tea conclusions

158 2.1.33 Spartina (Spartina anglica, S. alterniﬂora, S.

“texttimes ”emphtownsendii) Proposed RPMS Category: Exclusion Overall impact: Major

Table 2.238: Relevant biology

Attribute Description Form Robust erect perennial growing up to 1 m tall. Habitat Mainly in saline wetlands, especially in estuaries where it forms dense mats in inter-tidal zones. Prefers deep, soft mud with a sandy loam texture. Can establish in the tidal ends of streams and rivers. Regional distribution Tauranga Harbour, Ohiwa Harbour and Maketu estuary. Competitive ability Once established forms dense stands, which may spread at a rate of 2% per annum. Reproductive ability S. anglica reproduces by seed. S. alterniflora rarely flowers in New Zealand. S.xtownsendii is a sterile hybrid. Dispersal methods Seed and vegetative fragments carried by water. Planted to aid foreshore protection and stabilize marshes due to its ability to trap sediment. Also to assist reclamation of tidal flats. Resistance to control Well controlled with herbicide. Benefits Prevents erosion at estuary margins.

Table 2.239: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity M H Traps sediment, raising level above high 1, 2, 3 tide mark, destroys intertidal zone and habitat. Adventive grasses succeed spartina, creating dry meadows. Immense biodiversity loss. Threatened species L H 1, 2, 3 Soil resources - - 4 Water quality M H Can reduce large estuaries and shallow 2, 3 harbours to thin drains surrounded by rough pasture. Production - - 2, 3 International trade - - 2, 3 Human health - - 2, 3 Recreation L H Dense stands obstruct access to estuaries 2, 3 and waterways. M¯aoriculture L H Smothers shellﬁsh beds, prevents 4 kaimoana harvesting. Source: 1: Craw (2000), 2: Anon. (2009l), 3: Anon. (2009f), 4: Severinsen (2003)

159 Spartina CBA results

Table 2.240: Spartina CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 6,398 0 0 -6,398 (2,397–20,244) (-2,397 – -20,244) Exclusion Pest 126 6,272 50,600 -44,328 (46–191) (2,351–20,053) (-48,249 – -30,547) Control Pest 333 6,065 33,030 -26,965 (116–535) (2,281–19,709) (-30,749 – -13,321) Advisory Pest 154 6,244 13,212 -6,968 (57–230) (2,340–20,014) (-10,872 – 6,802)

Table 2.241: Spartina CBA base assumptions.

Base assumptions Values Current area infested (ha) 10 Total area potentially infested (ha) 1,061 (355–1,766) Years from naturalisation to total area 75 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 2.95 (1–4.9) Any beneﬁts provided by the weed 1 Discount rate 0.08

Table 2.242: Spartina RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 1.2 (0–2.5)

Table 2.243: Spartina RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 6 (5–8)

Table 2.244: Spartina RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 12 (10–15)

160 Table 2.245: Spartina estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 7,500 2,500 1,000

Spartina conclusions

In the absence of regional control, the projected total regional damage in net present value is -$6,398 over the next 50 years (the minimum projected impact is -$2,397). Managing Spartina as an Exclusion pest has a projected net benefit to the region of -$44,328. Since this is negative, this means that this management scenario does not meets the requirements of Section 72(1a) of the Act. Managing Spartina as a Control pest has a projected net benefit to the region of -$26,965. Since this is negative, this means that this management scenario does not meet the requirements of Section 72(1a) of the Act. Managing Spartina as an Advisory pest has a projected net benefit to the region of -$6,968. Since this is negative, this means that this management scenario does not meet the requirements of Section 72(1a) of the Act. The proposed management scenario for Spartina, Exclusion, therefore fails to meet the requirements of Section 72(1a) of the Act. Spartina is an aggressive plant in estuaries that has been planted for erosion control but grows in thick monocultures excluding other species. The CBA is not cost beneficial because these impacts are not easy to quantify (it only has impacts on values in estuaries, which are hard to put dollar values on). It is also because spartina is an estuary specialist and so will never occur in a large area of the region (because of this, any multiplication of dollars per hectare ×area will produce a low number). It is therefore appropriate to treat the results of this CBA with skepticism. If the Council values the ecological integrity of the region’s estuaries and the ecosystem services they provide at more than $50,600 in total (in current dollars, for the full 50 years, not per year) over the next 50 years, this will still satisfy section 72(1a) of the Act for spartina to be managed as an Exclusion pest, as has been proposed.

161 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 10 0.4 Potential extent (ha): 1,061

(355−−1,766) Proportion extent of maximum 0.2 Time to potential (yr): 75

Current prop. of potential: 0.017 0.0

−20 0 20 40 60

Years from present

Figure 2.59: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

162 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

●

● ● ● 1.0 1.0 ● ● 1.0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 150 ● ● ● ● ● ● ● ● ● ● ● ● ● 0.8 0.8 ● ● 0.8 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 100 0.6 0.6 0.6

●

0.4 ● 0.4 0.4

● ● ● ● ● ● ● ● ● ● ● ● ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area 50 ● ● ● ● ● ● ● ● ● ● ● 0.2 0.2 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 163

1.0 ● 1.0 ● 1.0 ●

Discount rate: 0.08 ● 150 ● ● ● ● Total multiplier: 130.39 0.8 0.8 0.8 ● ● ●

(96−−258) ● ● ● ● 100 0.6 0.6 0.6 ●

● ●

●

● ● 0.4 0.4 ● 0.4 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual 50 cost Discounted annual cost Discounted annual ● ● ● ● ● ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 ● ● ● 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.60: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.34 Strawberry dogwood (Dendrobenthamia capitata)

Proposed RPMS Category: Advisory Overall impact: Moderate

Table 2.246: Relevant biology

Attribute Description Form Bushy evergreen tree to 6 m tall with oval grey-green leaves tapering to a long point, paler underneath, and densely covered in fine hairs. Pale yellow flowers, red strawberry-like bird-dispersed fruit. Habitat Disturbed forest, shrubland, grassland. Regional distribution Competitive ability Reproductive ability Produces viable seed. Dispersal methods Seed dispersed by birds. Resistance to control Unknown. Benefits Fruits are edible and used as a food source by native birds e.g. tui.

Table 2.247: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity L M-H In USA, other dogwoods grow into dense 1, 2, 3 thickets in grasslands which crowd out de- sired grasses, sedges and herbs, and alter wildlife habitat. In Australia it shades and crowds out understorey species in tall open forest. Threatened species L M 1, 2, 3 Soil resources - - Water quality - - Production L L Forms dense stands. 2, 3 International trade - - Human health - - Recreation - L Dense stands restrict access. 1, 2 M¯aoriculture - L See Recreation. 1, 2 Source: 1: Williams & Newﬁeld (2002), 2: Anon. (2009b), 3: Anon. (2007d)

164 Strawberry dogwood CBA results

Table 2.248: Strawberry dogwood CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 6,706,675 0 0 -6,706,675 (1,440,478–31,672,939) (-1,440,478 – -31,672,939) Exclusion Pest 2,537 6,704,138 16,866,597 -10,162,459 (646–4,099) (1,439,832–31,668,840) (-15,426,765 – 14,802,243) Control Pest 6,715 6,699,960 660,608 6,039,352 (1,625–11,485) (1,438,853–31,661,454) (778,245 – 31,000,846) Advisory Pest 3,111 6,703,564 13,212 6,690,352 (804–4,939) (1,439,674–31,668,000) (1,426,462 – 31,654,788)

Table 2.249: Strawberry dogwood CBA base assumptions.

Base assumptions Values Current area infested (ha) 90 Total area potentially infested (ha) 142,263 (47,904–236,623) Years from naturalisation to total area 25 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 6.62 (1.55–11.68) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.250: Strawberry dogwood RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 11.2 (0–22.5)

Table 2.251: Strawberry dogwood RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 56 (45–68)

Table 2.252: Strawberry dogwood RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5

165 Final area infested (ha) 112 (90–135)

Table 2.253: Strawberry dogwood estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 2,500,000 50,000 1,000

Strawberry dogwood conclusions

In the absence of regional control, the projected total regional damage in net present value is -$6,706,675 over the next 50 years (the minimum projected impact is -$1,440,478). Managing Strawberry dogwood as an Exclusion pest has a projected net benefit to the region of -$10,162,459. Since this is negative, this means that this management scenario does not meets the requirements of Section 72(1a) of the Act. Managing Strawberry dogwood as a Control pest has a projected net benefit to the region of $6,039,352. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Strawberry dogwood as an Advisory pest has a projected net benefit to the region of $6,690,352. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Strawberry dogwood, Advisory, therefore meets the requirements of Section 72(1a) of the Act.

166 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 90 0.4 Potential extent (ha): 142,263

(47,904−−236,623) Proportion extent of maximum 0.2 Time to potential (yr): 25

Current prop. of potential: 0.001 0.0

0 5 10 15 20 25

Years from present

Figure 2.61: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

167 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

●

● ● ● 1.0 1.0 ● ● 1.0 ● ● ● ● 2500 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.8 0.8 ● ● 0.8 ● ● 2000 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.6 ● 0.6 0.6 1500

●

● 1000 0.4 0.4 0.4 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ●

● ● 0.2 0.2 0.2 500 ●

● ●

● ● ● ● ● 0 ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 168

1.0 ● 1.0 ● 1.0 ● 2500 Discount rate: 0.08 ● ● ● ● Total multiplier: 4515.61 ● 0.8 0.8 ● 0.8 ● 2000 ● (2830−−12711) ● ● ● 0.6 0.6 ● 0.6 1500 ●

● ●

●

● ● 0.4 0.4 ● 0.4 1000 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● ● ● 0.2 0.2 ● 0.2 500 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.62: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.35 Variegated thistle (Silybum marianum)

Proposed RPMS Category: Control Overall impact: Moderate

Table 2.254: Relevant biology

Attribute Description Form Annual or biennial thistle growing up to 2 m high. Leaves are very prickly. Stem is hollow without spines. Flowers are large (7 cm in diameter) and red/purple in colour, only one flower per stem. Habitat Roadsides, pastures, gardens, wasteland. Grows best on high fertility soils. Regional distribution Limited distribution in Opotiki region. Competitive ability Very aggressive, forming dense impenetrable stands. Reproductive ability Flowers produce large numbers of seeds which may remain viable for years. Dispersal methods By wind or inclusion in hay bales. Resistance to control Spread of germination times increases diculty of control but is susceptible to several herbicides especially in seedling and rosette stage. Benefits Edible (young leaves, peeled young stems, roots, bases of flower heads) and used as medicinal plant (liver complaints).

Table 2.255: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity - - 1 Threatened species - - 1 Soil resources - - 1 Water quality - - 1 Production L M Forms dense patches, esp. on high fertil- 2, 3 ity soils. Prickles may damage stock and can cause nitrate poisoning in cattle and sheep. International trade - - 1 Human health - - 1 Recreation - M Dense patches of large, spiky plants are 2, 3 nasty to work through. M¯aoriculture - - 1 Source: 1: Severinsen (2003), 2: Roy et al. (2004), 3: Environment Bay of Plenty (2005i)

169 Variegated thistle CBA results

Table 2.256: Variegated thistle CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 5,879,862 0 0 -5,879,862 (1,133,833–28,187,995) (-1,133,833 – -28,187,995) Exclusion Pest 3,273 5,876,589 1,686,660 4,189,929 (702–5,465) (1,133,131–28,182,530) (-553,529 – 26,495,870) Control Pest 7,409 5,872,453 66,061 5,806,392 (1,528–12,920) (1,132,305–28,175,075) (1,066,244 – 28,109,014) Advisory Pest 3,433 5,876,429 13,212 5,863,217 (756–5,556) (1,133,077–28,182,439) (1,119,865 – 28,169,227)

Table 2.257: Variegated thistle CBA base assumptions.

Base assumptions Values Current area infested (ha) 10 Total area potentially infested (ha) 58,669 (20,583–96,756) Years from naturalisation to total area 75 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 65.72 (13.14–118.3) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.258: Variegated thistle RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 3.8 (2.5–5)

Table 2.259: Variegated thistle RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 6 (5–8)

Table 2.260: Variegated thistle RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5

170 Final area infested (ha) 12 (10–15)

Table 2.261: Variegated thistle estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 250,000 5,000 1,000

Variegated thistle conclusions

In the absence of regional control, the projected total regional damage in net present value is -$5,879,862 over the next 50 years (the minimum projected impact is -$1,133,833). Managing Variegated thistle as an Exclusion pest has a projected net benefit to the region of $4,189,929. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Variegated thistle as a Control pest has a projected net benefit to the region of $5,806,392. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Variegated thistle as an Advisory pest has a projected net benefit to the region of $5,863,217. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Variegated thistle, Control, therefore meets the requirements of Section 72(1a) of the Act.

171 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 10 0.4 Potential extent (ha): 58,669

(20,583−−96,756) Proportion extent of maximum 0.2 Time to potential (yr): 75

Current prop. of potential: <0.01 0.0

0 20 40 60

Years from present

Figure 2.63: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

172 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

●

● ● ● 1.0 1.0 ● ● 1.0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● 8000 ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.8 0.8 ● ● 0.8 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 6000 ● ● ● ● ● ●

0.6 ● 0.6 0.6

●

4000 ●

0.4 ● 0.4 0.4 ● ● ● ● ● ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● ● ● ● 2000 ● ● 0.2 0.2 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 173

1.0 ● 1.0 ● 1.0 ●

Discount rate: 0.08 ● 8000 ● ● ● ● Total multiplier: 2279.12 ● 0.8 0.8 ● 0.8 ●

● (1382−−6495) ● 6000 ●

● 0.6 ● 0.6 0.6 ●

● ● ●

4000 ● ● 0.4 0.4 ● 0.4 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual ● cost Discounted annual ● ● ● ● ● 2000 ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.64: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.36 Water poppy (Hydrocleys nymphoides)

Proposed RPMS Category: Exclusion Overall impact: Moderate

Table 2.262: Relevant biology

Attribute Description Form Stoloniferous with tufts of thick, shining leaves and a distinctive solitary yellow ﬂower. Habitat Grows well in warm, well lit, nutrient rich habitats. Aggressively colonises ponds, streams, farm dams and lake margins where it can spread to depths of 2 m. Regional distribution Believed to be eradicated from one site at Te Puke and one site at Ro- torua. Competitive ability Completely replaces with surface blanket vegetation. Reproductive ability No viable seed produced in New Zealand. Dispersal methods Solely vegetative. Plantlets produced along stolons, which detach and ﬂoat to surface and eventually take root. Mostly spread by humans as pond plant. Resistance to control Mechanical control likely to promote spread of plant. Can be controlled with herbicides.

Table 2.263: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity - H Forms dense patches in wetlands, ponds, 1 out-competes other vegetation. Threatened species - M 1 Soil resources - - 2 Water quality - L Mats choke waterways and impede 1 drainage. Production - - 2 International trade - - 2 Human health - - 2 Recreation - M Dense mats restrict access to waterways 1 for ﬁshing, swimming, kayaking etc. M¯aoriculture - M See Recreation. 3 Source: 1: Auckland Regional Council (2010b), 2: Severinsen (2003), 3: Stahl (2009)

174 Water poppy CBA results

Since Water poppy is currently absent from the region, it is dicult to accurately quantify the costs and beneﬁts of current and proposed e↵orts to continue to exclude the species. If the species were to invade this year and spread in the region, without regional control for the next 50 years, the total pest impacts over this period in net present value are calculated to be $106,639 ($47,878– $188,615). This can be compared with the calculated net present value of the proposed annual expenditure on control over this same period of $6,747 (Exclusion pest). Note that this comparison does not take into account whether or not the proposed level of expenditure is adequate to have a high probability of excluding the species over this period. Given the broad experience of the biosecurity sta↵ at Environment Bay of Plenty, we assume that it will be. The following tables provide the parameters used in this cost-beneﬁt analysis.

Table 2.264: Water poppy CBA base assumptions.

Table 2.265: Water poppy estimated total annual cost of the proposed RPMS scenario (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Year Total Costs 1.00 1,000

Water poppy conclusions

175 2.1.37 White-edged nightshade (Solanum marginatum)

Proposed RPMS Category: Exclusion Overall impact: Major

Table 2.266: Relevant biology

Attribute Description Form Much branched perennial shrub to small tree to 5 m tall. Prickles 1.5 cm only on stems and leaves. White felted twigs, white marginal zones on upper surface of mature leaves. Habitat Mainly in scrub, poor rough country, roadsides, wastelands and bush margins in warm, sunny situations. Regional distribution Isolated on Matakana Island and Mt Maunganui. Competitive ability Forms dense impenetrable thickets. Can invade poor open pasture and other open areas. Reproductive ability Produces moderate amounts of seeds. Flowers within 5-7 months of germination. Dispersal methods Seeds spread by soil movement and livestock. Resistance to control Regrows strongly after mechanical damage. Susceptible to picloram.

Table 2.267: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity L M Forms dense stands, displaces native 1, 2 species. Threatened species - L 2 Soil resources - - 1 Water quality - - 3 Production L H Shades out and displaces pasture species. 2, 4 Toxic to stock. International trade - - 3 Human health - L Poisonous. 3 Recreation - M Has prickly spines, dense impenetrable 3 stands are dicult to get through. M¯aoriculture L M On Matakana Island. 1 Source: 1: Stahl (2009), 2: Anon. (2007g), 3: Severinsen (2003), 4: Environment Bay of Plenty (2004a)

176 White-edged nightshade CBA results

Table 2.268: White-edged nightshade CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 37,143,299 0 0 -37,143,299 (14,675,917–149,407,198) (-14,675,917 – -149,407,198) Exclusion Pest 2,151 37,141,148 10,120 37,131,028 (457–3,627) (14,675,460–149,403,571) (14,665,340 – 149,393,451) Control Pest 4,518 37,138,781 13,212 37,125,569 (920–7,990) (14,674,997–149,399,208) (14,661,785 – 149,385,996) Advisory Pest 1,990 37,141,309 6,606 37,134,703 (362–3,904) (14,675,555–149,403,294) (14,668,949 – 149,396,688)

Table 2.269: White-edged nightshade CBA base assumptions.

Base assumptions Values Current area infested (ha) 6 Total area potentially infested (ha) 130,154 (43,408–216,901) Years from naturalisation to total area 50 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 62.88 (12.58–113.18) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.270: White-edged nightshade RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 3.8 (3–4.5)

Table 2.271: White-edged nightshade RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 5 (5–6)

Table 2.272: White-edged nightshade RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5

177 Final area infested (ha) 8 (9–6)

Table 2.273: White-edged nightshade estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Sub- sequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 1,500 1,000 500

White-edged nightshade conclusions

In the absence of regional control, the projected total regional damage in net present value is -$37,143,299 over the next 50 years (the minimum projected impact is -$14,675,917). Managing White-edged nightshade as an Exclusion pest has a projected net benefit to the region of $37,131,028. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing White-edged nightshade as a Control pest has a projected net benefit to the region of $37,125,569. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing White-edged nightshade as an Advisory pest has a projected net benefit to the region of $37,134,703. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for White-edged nightshade, Exclusion, therefore meets the requirements of Section 72(1a) of the Act.

178 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 6 0.4 Potential extent (ha): 130,154

(43,408−−216,901) Proportion extent of maximum 0.2 Time to potential (yr): 50

Current prop. of potential: <0.01 0.0

0 10 20 30 40 50

Years from present

Figure 2.65: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

179 Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory control

● ● ● ● ● ● ● ● 1.0 1.0 ● ● ● ● 1.5 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 30000 ● ● 0.8 0.8 ● ● ●

● ● ● 1.0 ● ● 0.6 0.6 20000

0.4 0.4

● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.5 ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● 10000 ● ● ● ● 0.2 0.2 ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 180

1.0 ● 1.0 ● 1.0 ●

● Discount rate: 0.08 ● ● ● 30000 ● ● ● Total multiplier: 22307.16 0.8 0.8 ● 0.8

● ● (13386−−66884) ● ● ● 0.6 0.6 0.6 ● ●

20000 ●

● ●

● ● ● 0.4 ● 0.4 ● 0.4 ● ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● 10000 ● ● ● ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.66: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.38 Wild ginger (yellow and kahili) (Hedychium gardnerianum, H. ﬂavescens)

Proposed RPMS Category: Control Overall impact: Major

Table 2.274: Relevant biology

Attribute Description Form Both gingers have large green leaves with spikes and scented ﬂowers and can grow up to 2-3 m tall, with massive branching surface rhizomes. Flowers of kahili ginger are yellow with red stamens. Yellow ginger has creamy ﬂowers. Habitat Thrives in warm damp areas, very shade tolerant. Regional distribution Found in most parts of region. Competitive ability Both gingers spread rapidly from large rhizomes which form thick mats up to 1 m deep in the soil. Can suppress 90% of native vegetation. Reproductive ability Kahili ginger produces up to 100 seeds per head. Yellow ginger does not produce seed. Dispersal methods Kahili ginger produces seed which is spread by birds. Spread also by dumping garden waste. Resistance to control Can be controlled using herbicides. Removal by hand dicult due to size of rhizomes.

Table 2.275: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity M H Forms dense patches and out-competes al- 1, 2 most all native species, prevents forest regeneration. Threatened species L H 1, 2 Soil resources - L Shallow-rooted, deep rhizome beds be- 1 come heavy with rain and slip on steep sites and streambanks, causing erosion. Water quality - - 3 Production L L Established in pine blocks. 4, 5 International trade - - 3 Human health - - 3 Recreation L M Dense patches restrict access. 3 M¯aoriculture L M Obstructs access to cultural sites (e.g. 3 waahi tapu, urupa). Source: 1: Craw (2000), 2: Williams et al. (2003), 3: Severinsen (2003), 4: Department of Conservation (1997b), 5: Mather (2009)

181 Wild ginger (yellow and kahili) CBA results

Table 2.276: Wild ginger (yellow and kahili) CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 1,388,662 0 0 -1,388,662 (331,515–4,181,345) (-331,515 – -4,181,345) Exclusion Pest 44,659 1,344,003 15,854,602 -14,510,599 (10,622–72,788) (320,893–4,108,557) (-15,533,709 – -11,746,045) Control Pest 118,216 1,270,446 620,972 649,474 (26,730–203,947) (304,785–3,977,398) (-316,187 – 3,356,426) Advisory Pest 54,773 1,333,889 13,212 1,320,677 (13,220–87,710) (318,295–4,093,635) (305,083 – 4,080,423)

Table 2.277: Wild ginger (yellow and kahili) CBA base assumptions.

Base assumptions Values Current area infested (ha) 700 Total area potentially infested (ha) 100,702 (34,134–167,271) Years from naturalisation to total area 75 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 14.98 (3.28–26.68) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.278: Wild ginger (yellow and kahili) RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 87.5 (0–175)

Table 2.279: Wild ginger (yellow and kahili) RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 438 (350–525)

Table 2.280: Wild ginger (yellow and kahili) RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5

182 Final area infested (ha) 875 (700–1,050)

Table 2.281: Wild ginger (yellow and kahili) estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 2,350,000 47,000 1,000

Wild ginger (yellow and kahili) conclusions

In the absence of regional control, the projected total regional damage in net present value is -$1,388,662 over the next 50 years (the minimum projected impact is -$331,515). Managing Wild ginger (yellow and kahili) as an Exclusion pest has a projected net benefit to the region of -$14,510,599. Since this is negative, this means that this management scenario does not meets the requirements of Section 72(1a) of the Act. Managing Wild ginger (yellow and kahili) as a Control pest has a projected net benefit to the region of $649,474. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Wild ginger (yellow and kahili) as an Advisory pest has a projected net benefit to the region of $1,320,677. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Wild ginger (yellow and kahili), Control, therefore meets the requirements of Section 72(1a) of the Act.

183 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 700 0.4 Potential extent (ha): 100,702

(34,134−−167,271) Proportion extent of maximum 0.2 Time to potential (yr): 75

Current prop. of potential: 0.012 0.0

−20 0 20 40 60

Years from present

Figure 2.67: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

184 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

●

● ● ● 1.0 1.0 ● ● 1.0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 200 ● ● ● ● ● ● ● ● ● ● ● 0.8 0.8 ● ● 0.8 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 150 ● ● ● ● 0.6 ● 0.6 0.6

●

100 0.4 ● 0.4 0.4

● ● ● ● ● ● ● ● ● ● ● ● ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● ● ● ● ● ● ● ● 50 ● ● 0.2 0.2 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 185

1.0 ● 1.0 ● 1.0 ●

Discount rate: 0.08 ● 200 ● ● ● ● Total multiplier: 158.03 0.8 0.8 0.8 ● ● ●

(116−−313) ● ● 150 ● 0.6 0.6 ● 0.6 ●

● ●

●

● 100 ● 0.4 0.4 ● 0.4 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● ● 50 ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 ● 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.68: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.39 Wild kiwifruit (Actinidia spp.)

Proposed RPMS Category: Control Overall impact: Major

Table 2.282: Relevant biology

Attribute Description Form Vigorous perennial vine up to 15 m. Climbing or straggling. Habitat Exotic and native forest, particularly on the margins and in light gaps, regenerating forest, riparian margins, and scrub. Usually close to kiwifruit orchards or where excess fruit has been dumped or fed to stock. Regional distribution Te Puke and Katikati areas, isolated elsewhere. Competitive ability Can smother or strangle host plants. Very vigorous grower. Reproductive ability Each fruit contains numerous small seeds. Dispersal methods Birds and stock can spread seed. Fruit also distributed by dumping or used as stock food for cattle and deer. Resistance to control Can be cut and treated with herbicide or sprayed during spring and summer. Beneﬁts Edible fruit. Reject export fruit used as livestock feed.

Table 2.283: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity L H Smothers canopy trees with dense vines 1 and causes collapse. Threatened species - M 1 Soil resources - - 2 Water quality - - 2 Production L M Smothers trees in plantation forests and 3, 4 orchards. Prevents access and creates safety hazard during harvest of plantation trees. International trade - - 2 Human health - - 2 Recreation - M Dense walls of vines restrict access to for- 2 est. M¯aoriculture - L See Recreation. 2 Source: 1: Gianotti (2002), 2: Severinsen (2003), 3: Environment Bay of Plenty (2004a), 4: Environment Bay of Plenty (2005e)

186 Wild kiwifruit CBA results

Table 2.284: Wild kiwifruit CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 1,417,966 0 0 -1,417,966 (364,748–6,652,469) (-364,748 – -6,652,469) Exclusion Pest 2,940 1,415,026 10,119,958 -8,704,932 (638–4,845) (364,110–6,647,624) (-9,755,848 – -3,472,334) Control Pest 7,783 1,410,183 396,365 1,013,818 (1,604–13,574) (363,144–6,638,895) (-33,221 – 6,242,530) Advisory Pest 3,606 1,414,360 13,212 1,401,148 (793–5,838) (363,955–6,646,631) (350,743 – 6,633,419)

Table 2.285: Wild kiwifruit CBA base assumptions.

Base assumptions Values Current area infested (ha) 50 Total area potentially infested (ha) 143,637 (48,341–238,933) Years from naturalisation to total area 100 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 13.81 (2.76–24.86) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.286: Wild kiwifruit RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 6.2 (0–12.5)

Table 2.287: Wild kiwifruit RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 31 (25–38)

Table 2.288: Wild kiwifruit RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 62 (50–75)

187 Table 2.289: Wild kiwifruit estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 1,500,000 30,000 1,000

Wild kiwifruit conclusions

In the absence of regional control, the projected total regional damage in net present value is -$1,417,966 over the next 50 years (the minimum projected impact is -$364,748). Managing Wild kiwifruit as an Exclusion pest has a projected net benefit to the region of - $8,704,932. Since this is negative, this means that this management scenario does not meets the requirements of Section 72(1a) of the Act. Managing Wild kiwifruit as a Control pest has a projected net benefit to the region of $1,013,818. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Wild kiwifruit as an Advisory pest has a projected net benefit to the region of $1,401,148. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Wild kiwifruit, Control, therefore meets the requirements of Section 72(1a) of the Act.

188 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 50 0.4 Potential extent (ha): 143,637

(48,341−−238,933) Proportion extent of maximum 0.2 Time to potential (yr): 100

Current prop. of potential: 0.001 0.0

0 20 40 60 80 100

Years from present

Figure 2.69: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

189 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

●

● ● ● 1.0 1.0 ● ● 1.0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 2000 ● ● ● ● ● ● ● 0.8 0.8 ● ● 0.8 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 1500 ● ● 0.6 ● 0.6 0.6

●

1000 0.4 ● 0.4 0.4

● ● ● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● ● ● ● 500 ● ● 0.2 0.2 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 190

1.0 ● 1.0 ● 1.0 ●

Discount rate: 0.08 ● ● ● ● 2000 ● Total multiplier: 390.96 0.8 0.8 0.8 ● ● ●

(308−−1089) ● ● 1500 ● 0.6 0.6 ● 0.6 ●

● ●

●

● 1000 ● 0.4 0.4 ● 0.4 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual cost Discounted annual cost Discounted annual ● ● ● ● ● 500 ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.70: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.40 Wild purple loosestrife (Lythrum salicaria)

Proposed RPMS Category: Exclusion Overall impact: Moderate

Table 2.290: Relevant biology

Attribute Description Form Hairy, perennial herb. Stems erect and pink towards the base. Leaves have a hairy underside. Flowers are terminal, densely hairy and a rose- purple colour. Blackish seeds. Habitat Occasionally cultivated, damp places along stream banks, ditches and lakesides. Occasionally in dry wasteland. Regional distribution Few naturalised locations are known. Competitive ability Signiﬁcant, especially in wetland areas. Reproductive ability Seed viability not known in New Zealand, but has spread extensively in North America. Dispersal methods Dumped garden refuse and by seed. Resistance to control May be dicult to control in wetland situations.

Table 2.291: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity - H Forms dense stands in wetlands, out- 1 competes native species. Threatened species - M 1 Soil resources - - 1 Water quality - M Can clog up waterways and impede 2 drainage. Production - - 1 International trade - - 1 Human health - - 1 Recreation - M Blocks up and obstructs access to water- 1 ways. M¯aoriculture - M See Recreation. 1 Source: 1: Severinsen (2003), 2: Anon. (2006d)

191 Wild purple loosestrife CBA results

Since Wild purple loosestrife is currently absent from the region, it is dicult to accurately quantify the costs and beneﬁts of current and proposed e↵orts to continue to exclude the species. If the species were to invade this year and spread in the region, without regional control for the next 50 years, the total pest impacts over this period in net present value are calculated to be $57,781 ($25,417–$103,250). This can be compared with the calculated net present value of the proposed annual expenditure on control over this same period of $6,747 (Exclusion pest). Note that this comparison does not take into account whether or not the proposed level of expenditure is adequate to have a high probability of excluding the species over this period. Given the broad experience of the biosecurity sta↵ at Environment Bay of Plenty, we assume that it will be. The following tables provide the parameters used in this cost-beneﬁt analysis.

Table 2.292: Wild purple loosestrife CBA base assumptions.

Base assumptions Values Current area infested (ha) 0 Total area potentially infested (ha) 103,009 (34,775–171,242) Years from naturalisation to total area 75 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 1 (1–1) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.293: Wild purple loosestrife estimated total annual cost of the proposed RPMS scenario (includes inspection, control, monitoring, enforcement, administration etc.). Sub- sequent years are assumed to have the same value as the last year listed.

Exclusion Pest Year Total Costs 1.00 1,000

Wild purple loosestrife conclusions

192 2.1.41 Woolly nightshade (Solanum mauritianum)

Proposed RPMS Category: Control (deﬁned areas) Overall impact: Major

Table 2.294: Relevant biology

Attribute Description Form A perennial shrub or small tree of up to 4 m high. Leaves are grey green, ovate and densely covered with furry hairs. Violet ﬂowers and a dull yellow berry. Habitat Able to establish in a wide variety of climates and soil types. Habitat limitations not well known in New Zealand. Regional distribution Widespread throughout coastal areas. Competitive ability Can eliminate other species in dense stands. E↵ects on native bush not well known. Some believe that it will be shaded out over time, while others think it will continue to dominate. Reproductive ability Large numbers of seeds produced with 95% viability. 3 year-old plants recorded bearing 10,000 seeds. Dispersal methods Most seeds fall close to parent. Some spread by birds. Resistance to control Control by herbicides, cut and stump treatment, ring-barking, basal treatment and hand pulling.

Table 2.295: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity M H Forms dense, often pure stands. Inhibits 1 recruitment of native species, slows regeneration rate. Threatened species L H 1 Soil resources - - 2 Water quality - - 2 Production L L Forms dense stands on rough pasture, 1, 3 thought to be toxic to stock. International trade - - 2 Human health L M Can cause skin irritation and respiratory 1 problems in some people. Recreation L L Forms dense stands which obstruct access. 1 M¯aoriculture - L See Recreation. 1 Source: 1: Environment Bay of Plenty (2005k), 2: Severinsen (2003), 3: Environment Bay of Plenty (2004a)

193 Woolly nightshade CBA results

Table 2.296: Woolly nightshade CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 6,577,470 0 0 -6,577,470 (1,726,004–11,428,937) (-1,726,004 – -11,428,937) Exclusion Pest 166,770 6,410,700 33,733,195 -27,322,495 (37,616–273,542) (1,688,388–11,155,395) (-32,044,807 – -22,577,800) Control Pest 441,454 6,136,016 1,321,216 4,814,800 (94,658–766,448) (1,631,346–10,662,489) (310,130 – 9,341,273) Advisory Pest 204,540 6,372,930 13,212 6,359,718 (46,817–329,622) (1,679,187–11,099,315) (1,665,975 – 11,086,103)

Table 2.297: Woolly nightshade CBA base assumptions.

Base assumptions Values Current area infested (ha) 1,500 Total area potentially infested (ha) 34,500 (34,500–34,500) Years from naturalisation to total area 25 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 26.11 (5.43–46.79) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.298: Woolly nightshade RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 187.5 (0–375)

Table 2.299: Woolly nightshade RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 938 (750–1,125)

Table 2.300: Woolly nightshade RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5

194 Final area infested (ha) 1,875 (1,500–2,250)

Table 2.301: Woolly nightshade estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 5,000,000 100,000 1,000

Woolly nightshade conclusions

In the absence of regional control, the projected total regional damage in net present value is -$6,577,470 over the next 50 years (the minimum projected impact is -$1,726,004). Managing Woolly nightshade as an Exclusion pest has a projected net benefit to the region of -$27,322,495. Since this is negative, this means that this management scenario does not meets the requirements of Section 72(1a) of the Act. Managing Woolly nightshade as a Control pest has a projected net benefit to the region of $4,814,800. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Woolly nightshade as an Advisory pest has a projected net benefit to the region of $6,359,718. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Woolly nightshade, Control (defined areas), therefore meets the requirements of Section 72(1a) of the Act.

195 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 1,500 0.4 Potential extent (ha): 34,500

Time to potential (yr): 25 Proportion extent of maximum 0.2 Current prop. of potential: 0.043

0.0

−10 −5 0 5 10 15 20 25

Years from present

Figure 2.71: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

196 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

●

● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 1.0 1.0 ● 1.0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 20 ● ● ● ● ● ● ● ● ● ● ● ● 0.8 0.8 ● ● 0.8 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 15 ● ● 0.6 ● 0.6 0.6 ●

●

● 10 0.4 ● 0.4 0.4

● ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area

● ● 0.2 0.2 0.2 5 ●

● ●

● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 197

1.0 ● 1.0 ● 1.0 ●

Discount rate: 0.08 ● ● 20 ● ● ● Total multiplier: 171.45 0.8 0.8 0.8 ● ● ●

(171−−171) ● ● 15 ● 0.6 0.6 ● 0.6 ●

● ●

●

● 10 ● 0.4 0.4 ● 0.4 ● ● ● ● ● ● ● ● ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual ● cost Discounted annual cost Discounted annual ● ● ● ● ● ● ● ● ● ● ● 5 ● ● ● ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 0.0 0.0 ● ● ● ● ● 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.72: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.42 Yellow ﬂag iris (Iris pseudacorus)

Proposed RPMS Category: Control Overall impact: Major

Table 2.302: Relevant biology

Attribute Description Form Leafy perennial semi-aquatic iris growing up to 2 m. Produces large yellowish ﬂowers. Rhizomes form dense ﬂoating mats. Above ground portions die back if frosted. Habitat Water plant, growing around margins of ponds, swamps, rivers, waterways, drains. Tolerant of a wide range of situations including salinity, frost and complete submergence. Regional distribution Isolated infestations throughout region. Competitive ability Vegetative growth from rhizomes, tall dense growth habit. Has possible potential to displace virtually all species from the water’s edge margin. Relatively slow rate of spread but now sets viable seed. Reproductive ability Produces viable seed. Dispersal methods Seeds dispersed by water and wind, sometimes by humans for gardens. Resistance to control Can be adequately controlled with metsulfuron and glyphosate, however this may damage surrounding plants.

Table 2.303: Impact evaluation

Category Current Potential Comment Source impact impact Species diversity L M Dense patches and rhizome mats displace 1 native plants, esp. vulnerable marginal species. Poisonous seeds may have impact on birdlife. Threatened species L M 1 Soil resources - - 2 Water quality L M Can cause ﬂooding and changes in water 1 levels in swamps. Production - L Excludes pasture species. Causes gastro- 3 enteritis in cattle. International trade - - 2 Human health - - 2 Recreation L H Dense stands obstruct access to estuaries 2 and waterways. M¯aoriculture L M See Recreation. 2 Source: 1: Craw (2000), 2: Severinsen (2003), 3: Environment Bay of Plenty (2005l)

198 Yellow ﬂag iris CBA results

Table 2.304: Yellow ﬂag iris CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values.

Scenario Pest impacts Control beneﬁt Expenditure Net beneﬁt No RPMS 71,566 0 0 -71,566 (13,528–356,940) (-13,528 – -356,940) Exclusion Pest 11 71,555 927,663 -856,108 (2–19) (13,526–356,921) (-914,137 – -570,742) Control Pest 30 71,536 36,333 35,203 (6–52) (13,522–356,888) (-22,811 – 320,555) Advisory Pest 14 71,552 13,212 58,340 (3–22) (13,525–356,918) (313 – 343,706)

Table 2.305: Yellow ﬂag iris CBA base assumptions.

Base assumptions Values Current area infested (ha) 5 Total area potentially infested (ha) 101,447 (34,289–168,604) Years from naturalisation to total area 100 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 0.53 (0.1–0.96) Any beneﬁts provided by the weed 0 Discount rate 0.08

Table 2.306: Yellow ﬂag iris RPMS Exclusion Pest assumptions.

Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 0.6 (0–1.2)

Table 2.307: Yellow ﬂag iris RPMS Control Pest assumptions.

Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 3 (2–4)

Table 2.308: Yellow ﬂag iris RPMS Advisory Pest assumptions.

Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 6 (5–8)

199 Table 2.309: Yellow ﬂag iris estimated total annual cost of di↵erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed.

Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 1.00 137,500 2,750 1,000

Yellow ﬂag iris conclusions

In the absence of regional control, the projected total regional damage in net present value is -$71,566 over the next 50 years (the minimum projected impact is -$13,528). Managing Yellow flag iris as an Exclusion pest has a projected net benefit to the region of -$856,108. Since this is negative, this means that this management scenario does not meets the requirements of Section 72(1a) of the Act. Managing Yellow flag iris as a Control pest has a projected net benefit to the region of $35,203. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Yellow flag iris as an Advisory pest has a projected net benefit to the region of $58,340. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Yellow flag iris, Control, therefore meets the requirements of Section 72(1a) of the Act.

200 Calibrated logistic growth curve, no RPMS control

1.0

0.8

0.6

Current extent (ha): 5 0.4 Potential extent (ha): 101,447

(34,289−−168,604) Proportion extent of maximum 0.2 Time to potential (yr): 100

Current prop. of potential: <0.01 0.0

0 20 40 60 80 100

Years from present

Figure 2.73: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report.

201 ●

● Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory● control ●

●

● ● ● 1.0 1.0 ● ● 1.0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 15000 ● ● ● ● ● ● ● ● ● ● ● ● ● 0.8 0.8 ● ● 0.8 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 10000 0.6 ● 0.6 0.6

●

0.4 ● 0.4 0.4

● ● ● 5000 ● Proportion of initial area Proportion of initial area Proportion of initial area Proportion of initial area ● ● ● ● ● ● 0.2 0.2 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years from present Years from present Years from present

Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 202

1.0 ● 1.0 ● 1.0 ●

Discount rate: 0.08 ● 15000 ● ● ● ● Total multiplier: 2596.88 0.8 0.8 0.8 ● ● ●

(1563−−7681) ● ● ● 10000 0.6 0.6 ● 0.6 ●

● ●

●

● ● 0.4 0.4 ● 0.4 ● ● ● ● Discounted annual cost Discounted annual Discounted annual cost Discounted annual 5000 cost Discounted annual cost Discounted annual ● ● ● ● ● ● 0.2 0.2 ● 0.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.0 0.0

0 10 20 30 40 50 0 2 4 6 8 0 10 20 30 40 50 0 1 2 3 4 5

Years from present Years of control Years of control Years of control

(a) (b) (c) (d)

Figure 2.74: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 2.1.43 Pest plant beneﬁciaries and exacerbators

The tables on the following pages identify those in the Bay of Plenty community most likely to beneﬁt from pest control (“beneﬁciaries”) and those most likely to exacerbate pest spread or impacts (“exacerbators”).

203 Table 2.310: Beneﬁciaries for pest plants

Plant RPMS category Pastoral Horticulture Forestry Urban Regional community African feather grass Control Major Minor Major Apple of Sodom Control Major Minor Asiatic knotweed Control Major Boneseed Control Major Chilean rhubarb Control Major Climbing spindleberry Control Minor Major Coast tea tree Control Major Darwin’s barberry Control Minor Major Egeria densa Control (defined lakes) Major Green goddess lily Control Major Major Hornwort Control (defined lakes) Major Italian buckthorn Control Minor Major Lagarosiphon Control (defined lakes) Major Lantana Control Minor Major Lodgepole pine Control Minor Minor Major 204 Old man’s beard Control Minor Major Royal fern Control Major Variegated thistle Control Major Minor Wild ginger (yellow and kahili) Control Minor Major Wild kiwifruit Control Minor Major Major Woolly nightshade Control (defined areas) Minor Minor Major Major Major Yellow flag iris Control Major Table 2.311: Exacerbators for pest plants

Plant RPMS category Pastoral Horticulture Forestry Urban Regional community African feather grass Control Minor Minor Apple of Sodom Control Minor Asiatic knotweed Control Minor Minor Boneseed Control Minor Chilean rhubarb Control Major Minor Climbing spindleberry Control Minor Coast tea tree Control Major Major Darwin’s barberry Control Minor Egeria densa Control (defined lakes) Major Green goddess lily Control Major Major Hornwort Control (defined lakes) Major Italian buckthorn Control Major Major Lagarosiphon Control (defined lakes) Major Lantana Control Minor Lodgepole pine Control Minor Major 205 Old man’s beard Control Minor Major Royal fern Control Variegated thistle Control Minor Wild ginger (yellow and kahili) Control Major Major Wild kiwifruit Control Minor Major Minor Woolly nightshade Control (defined areas) Minor Minor Minor Major Yellow flag iris Control Minor Major