Section 4: Focus on Canterbury

Coastal dune biodiversity — challenges for management

Philip Grove Environment Canterbury PO Box 345, Christchurch, [email protected]

ABSTRACT The natural character and physical form of Christchurch’s coastal dune systems have been greatly changed since European settlement, with consequent loss of native biodiversity. Under the Christchurch Beaches and Coastal Parks Management Plan, management of the Christchurch coastline is the responsibility of the City’s Parks and Waterways Unit1 and managed under the ‘Coast Care’ programme.

One of the main objectives of the Parks and Waterways Unit’s coastal management plan is to preserve, and where possible re-establish, the indigenous ecology of the Christchurch coastal environment, with an emphasis on indigenous wildlife habitats. The challenges to meeting this objective include the often- conflicting demands of urban development and public access for recreation.

This paper provides an overview of coastal dune biodiversity in Christchurch, looks at some of the opportunities for protecting and enhancing this biodiversity, and examines the challenges posed by people, their pets and their vehicles. The question is, to what extent are we, the public, prepared to change or constrain the way we access, use and manage coastal dune systems, so that there can still be a place for the original inhabitants, the native flora and fauna? The focus is on Christchurch, with brief reference to neighbouring coastal dune systems north and south of the City boundaries.

BACKGROUND — THE SOFT SAND DUNE BEACHES OF PEGASUS BAY AND KAITORETE SPIT Extensive soft sand dune systems occur on the Te Waihora / Lake Ellesmere from the Pacifi c Canterbury coastline at two distinct areas; north Ocean. The Spit, despite its offi cial name, is and south of Banks Peninsula at Pegasus Bay actually a barrier as it is connected at both and Kaitorete Spit. Pegasus Bay, extending ends. It is approximately 27 km long and tapers from Godley Head at the northern entrance of from a width of 5 km at its eastern end to 250 Lyttelton Harbour to Teviotdale, just north of the m at its western end. An extensive sand dune Waipara River, covers approximately 50 km of system backs the beach for most of the length the North Canterbury coastline. Pegasus Bay is of the spit. West and south of Kaitorete Spit, characterised by sandy beaches and associated there is a transition to the cobble beaches that dune systems for most of its length from characterise the mid- and South Canterbury Taylors Mistake in the south to approximately coastline. Leithfi eld in the north. North of Leithfi eld, beach sediments grade to mixed sand and This paper focuses on the dune systems of gravel, and sand dunes are not present (Cope the Christchurch City coastline, which occupy et al. 1998). The southern dune system is at the southern half of Pegasus Bay from Taylors Kaitorete Spit, and is located between Banks Mistake to the mouth of the Waimakariri River. Peninsula and the Rakaia River, and separates Reference will also be made to the neighbouring

1 Editor’s note: now known as the Greenspace Unit.

208 Greening the City. ISBN 0-959-77566-8 © Royal New Zealand Institute of Horticulture (Inc.) 2005 Section 4: Focus on Canterbury dune systems of north Pegasus Bay and formed access tracks so as to minimise damage Kaitorete Spit, with their contrasting patterns of to the dunes and vegetation. vegetation and land use. The coastal dune systems of North Pegasus The Christchurch coastline has the most Bay (i.e., north of the Waimakariri River mouth) highly modifi ed and actively managed dune are relatively undeveloped, in the sense that systems of these three coastal areas. With there is still for the most part a semi-natural the concentration of population in the adjoining foredune-backdunes sequence. However, like city comes a concentration of associated the Christchurch beaches, the North Pegasus environmental effects and development Bay dunes are dominated by exotic plant species, pressures. Along much of the Christchurch principally marram grass and lupin shrubs coastline, the width of the dune system has (Lupinus arboreus). Farmland and plantation been constrained by urban development to a forests adjoin the North Pegasus Bay dunes, and single artifi cially stabilised foredune, rather than there is localised spread of self-sown pines into the natural sequence of mobile foredune and the dune systems. A major and as yet unresolved more stable backdunes (Fig. 1). Management issue for the North Pegasus Bay dunes is damage of the beach and dunes is the responsibility of to the dune systems and disturbance of wildlife by the Christchurch City Council’s (CCC) Parks recreational vehicles (Fig. 2). and Waterways Unit. Under the Christchurch Beaches and Coastal Parks Management Plan The Kaitorete Spit dunes are for the most part (CCC 1995), present coastal management reserve land managed by the Department of seeks to: Conservation, although in places the dunes do extend back onto adjacent farmland. These • Provide coastal protection, using the dunes are unique in that they support what foredunes and beaches as a buffer between is probably the most extensive example of the sea and the urban areas and coastal indigenous dune vegetation in New Zealand parks. This can involve construction of sand (Courtney 1983). The dominant species fences, mechanical reshaping of dunes and is the native sand-binding sedge pīngao the planting of exotic dune-stabilising species, (Desmoschoenus spiralis), with a range of principally marram grass (Ammophila associated native sand dune herb, grass arenaria) and South African iceplant and shrub species also present. Pīngao was (Carpobrotus edulis) once widespread on New Zealand’s coastal • Carry out planting of native coastal species dunes, but has now largely been replaced by • Create/enhance habitat for native wildlife introduced marram grass. Management issues • Provide recreation opportunities for city for this nationally important conservation area residents and visitors (CCC 2000). are, again, damage by recreational vehicles, and the control of exotic plant and These management aims are not always species. compatible and are listed in order of importance (CCC 2000). Thus management activities VEGETATION HISTORY OF THE deemed necessary for coastal protection CHRISTCHURCH COASTAL DUNES purposes will take precedence over those Vegetation cover and dune form has changed designed to enhance wildlife habitat or dramatically in the 150 years since European recreation opportunities. Public vehicle access settlement. The earliest indications of historical to the Christchurch beaches is prohibited, vegetation cover are given by paintings, however except for the northernmost stretch of beach it is unknown exactly what cover existed before from Bottle Lake Forest Park to the Waimakariri European settlement. Botanical accounts from River where a permit system operates. As the late 19th and early 20th Century indicate there is heavy pedestrian use of the dunes and that, as at Kaitorete today (Fig. 3), pīngao was beaches, the Parks and Waterways Unit have the dominant species of the foredunes. The been working to direct pedestrian traffi c along native sand-binding spinifex grass (Spinifex

209 Section 4: Focus on Canterbury sericeus) was also present on the Christchurch A native dune vegetation planting programme foredunes and is believed to have reached its has been in operation since the mid-1990s. natural southern limit here (CCC 2000). Pīngao- An increasing number of pīngao plantings covered foredunes are characteristically wide have been established on foredune sections and gently-sloping, with considerable areas of of the Christchurch coast and spinifex has bare sand present around the pīngao plants. been successfully re-established at Taylors Backdune vegetation was apparently a mix Mistake. However, restoration of the pīngao of fl ax (Phormium tenax) in damp hollows population is limited by the availability of nursery surrounded by dense, low-statured mānuka stock, browsing by rabbits, competition from (Leptospermum scoparium) scrub that also marram grass and occasional disturbance contained a good deal of matagouri (Discaria of planting sites in storm events. Planting of toumatou) (Fig. 4; CCC 2000). native backdune species such as fl ax, ngaio (Myoporum laetum), taupata (Coprosma repens), Modifi cation started at a very early stage of cabbage trees (Cordyline australis) and akeake European settlement, as coastal areas were (Dodonaea viscosa) have to date proven more included in the early Canterbury sheep runs. A widely successful and sustainable. The Parks combination of grazing and burning would have and Waterways Unit have developed planting affected palatable native spinifex and pīngao, techniques to help these species establish in the while burning was used to clear mānuka scrub. harsh Christchurch coastal environment. By the late 1800s these practices had resulted in dune instability beyond the cycle of accretion Semi-natural dune systems on the Christchurch and erosion that would normally occur. Large coastline persist at Brooklands Spit and volumes of sand were blown inland over the Southshore Spit, where the dunes do not developing city and farmland. The rapid immediately adjoin developed urban areas. destruction of pīngao dunes by fi re and grazing These sites still have considerable value as resulted in a lowering and loss of dune form wildlife habitat. Exotic vegetation dominates at along much of southern Pegasus Bay. Without both sites, but there has been extensive native their stabilising vegetation, wandering dunes planting and habitat restoration carried out at developed and migrated up to 4 km inland Southshore Spit. The remaining dune systems (CCC 2000). of the Christchurch coastline are artifi cially constrained by urban development and because Plantings of exotic marram and lupin for dune of this and high human use offer limited stabilisation began in the 1870s, accelerated potential for wildlife, especially birds. over the 1890s, and has continued up to the present. In 1909, a City Council policy of NATIVE WILDLIFE OF THE CHRISTCHURCH afforestation was adopted in order to check COASTAL DUNES the advance of the dunes. Before pines could Invertebrates be planted, dune stabilisation and higher soil The katipō spider (Latrodectus katipo) is nutrient levels were required. Primary plantings endemic to New Zealand coastal dunes and of marram and lupin achieved these aims. In is present on the Christchurch coast (Fig. 5). little over 100 years, the natural coastal dune Web sites are generally located at the base of vegetation of pīngao and other plants has marram grass or pīngao and under driftwood been progressively removed and replaced by within a few hundred metres of the high tide exotics, principally marram and lupins (CCC mark. Research conducted at South Brighton 2000). The marram dunes of Christchurch and beach in the 1960s found that katipō were most north Pegasus Bay are now steeper and more abundant in sparse to medium densities of densely-vegetated than was the case when marram grass on steeply sloping ground facing pīngao was the dominant cover. This change north to west, quite specifi c habitat requirements in vegetation cover and dune form (e.g., Clifton (CCC 2000). Over the last 10 years, katipō 1979) has had implications for the value of the abundance has declined dramatically in dune systems as habitat for native wildlife. many areas around New Zealand and the

210 Section 4: Focus on Canterbury

Christchurch coast is no exception. An earlier Birds 1969 survey recorded katipō spider densities as Before European settlement the Christchurch high as 1.1 spiders per square metre at South coastal dunes hosted large breeding colonies Brighton Beach. A similar survey of the area of gulls and terns, as well as providing in the 1990s found only three spiders at South nesting sites for wading birds such as banded Brighton Beach. In the period between the two dotterel (Charadrius bicinctus) and variable surveys, the sand dunes have been extensively oystercatcher (Haematopus unicolor; Fig. 6), modifi ed by the Christchurch City Council for and white-fl ippered penguins (Eudyptula minor coastal protection purposes, with the installation albosignata). This is refl ected in the Māori of windbreak fencing, and the planting of sand- name for Southshore Spit — te karoro karoro binding succulents. Recent research has — translated as ‘cry of seagulls’. For the most shown that dune modifi cation, in combination part, these breeding colonies disappeared with the absence of driftwood and the increase within a few decades of European settlement. of dense marram on the Canterbury cost is Disturbance of these ground-nesting birds linked to low katipō numbers (CCC 2000). by humans and dogs, reduction in habitat arising from the spread of exotic vegetation, Although there is little information on other and predation by introduced mammals were indigenous coastal dune invertebrates, it is all causal factors. These factors have all expected that the native planting on the back worsened with increased population, easier dunes should increase available habitat and access for vehicles, beach erosion and an food supply for these species. almost total smothering of suitable nesting sites by vegetation. Lizards At least one, and possibly two, species of native At present, the south side of the Waimakariri ( maccani and O. nigriplantare River still remains an important roosting site polychroma) occur in the Christchurch coastal for terns, gulls, cormorants and waders. In environment but identifi cation is diffi cult. Skink recent years there has been limited nesting of populations probably increased in association threatened banded dotterel above the high tide with forest clearance and wetland drainage mark on Brooklands Spit (Fig. 7). However, associated with the early development of the reappearance of nesting dotterel here Christchurch, but with ongoing urbanisation skink remains tenuous because the area of suitable populations are again likely to be in decline. habitat is restricted to the narrow zone of bare sand and driftwood between the high tide mark Both common gecko (Hoplodactylus maculatus) and the toe of the marram-covered foredunes, and jewelled gecko (Naultinus gemmeus) and is vulnerable to passing vehicles. The tip were recorded from New Brighton before of Southshore Spit is a nationally important 1955. Neither species appears to be present roosting site for waders, cormorants, gulls in the area now, although both species are and terns (Fig. 8) and often supports many present on the Port Hills. Replanting of native thousands of birds. Some suitable nesting species in the coastal zone is likely to enhance habitat does remain here but there has been lizard habitat. Small-leaved shrubs such as no nesting since the 1960s due to constant Coprosma species, porcupine scrub (Melicytus disturbance by people and dogs. alpinus), pōhuehue () and fl ax all provide food for lizards. At the same The Christchurch coastline between Brookland time however, continuing urbanisation of rural and Southshore spits offers no nesting or land on the outskirts of the city is destroying roosting areas (lack of habitat and human lizard habitat (CCC 2000). Predators such disturbance) although birds will visit to feed on as domestic cats take a heavy toll on lizards the sand fl ats at low tide and in the surf. The and without effective control will continue to remnant dune systems at Sumner and Taylors limit numbers even where habitat protection or Mistake beaches have similarly limited value as restoration takes place. bird habitat.

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THE CHALLENGE above the high tide mark than can be found The challenge now for the managers of the elsewhere on the Christchurch coast. Christchurch coastal dunes is how to more fully give effect to the objective of the coastal plan The exotic shrub weed boneseed that calls for: (Chrysanthemoides monilifera) is abundant at Southshore Spit forming dense patches ‘the preservation, and where possible re- in places. However, this infestation does establishment, of the indigenous ecology not appear intractable and a programme of of the Christchurch coastal environment, progressive eradication and replacement with with an emphasis on indigenous wildlife native species should be attempted here. habitats’. As mentioned earlier, Southshore Spit is a Two sections of the Christchurch coastline nationally important bird roosting site and offer the best potential for preservation and re- retains some suitable habitat for ground establishment of the indigenous ecology — the nesting birds. Progressive removal of marram tip of Southshore Spit and Brooklands Spit. grass and other weeds would improve Because these sections of coast do not back the available nesting habitat, particularly onto developed urban areas or farmland, it is if accompanied by control of mammalian less imperative to manage the dunes primarily predators. However, successful nesting will for coastal protection. The geography of both not occur while disturbance from people and these coastal dune areas also suggests they dogs continues here, regardless of other efforts could lend themselves to ‘mainland island’ type to enhance bird habitat. For the same reason, conservation management with an integrated the area’s full potential as roosting habitat programme of habitat restoration and intensive cannot be realised. During a recent revision of control of exotic pest species which could City Council dog control policy and regulations, also involve the construction of predator- excluding dogs from Southshore Spit for proof fences. Perhaps the best-known purposes of wildlife protection was suggested. mainland island example within an urban Such a change to current access regulations area of New Zealand is the Karori Wildlife was strongly opposed in public submissions sanctuary in Wellington. Another example and has not gone ahead. This suggests that under development is Tawharanui Peninsula, any restrictions on human access for the managed by Auckland Regional Council, which same reason would also be strongly opposed, includes areas of coastal dune habitat. although the idea has not been formally tested in the public arena. SOUTHSHORE SPIT The current spit shape is very different from its Animal pests, including rabbits and predators original surveyed boundary, indicating the highly such as cats, ferrets and rodents all threaten mobile nature of this dune system at the mouth the Spit’s indigenous biota. Southshore Spit of the Avon-Heathcote Estuary. This mobility supports a large rabbit population that takes has precluded development; the area still a particularly heavy toll on pīngao plantings. supports a relatively natural dune system and Rabbit poisoning has been carried out in the is managed as a recreation reserve. Remnants past, but there is reinvasion from the adjacent of native vegetation in the dune hollows have beach area and private properties. Poisoning of been supplemented by extensive replanting of rabbits and predators here remains problematic native foredune and backdune species. Wide because of the risk to children and dogs visiting sand fl ats are exposed on the beach at low tide the reserve (CCC 2000). but the area of backshore open sand is limited at high tide. Old photographs reveal that the Southshore Spit has massive potential for backshore area was formerly quite extensive, enhancement and restoration of Christchurch’s nevertheless Southshore Spit still retains more coastal dune biodiversity, but this potential sites of open or sparsely vegetated dunes is limited by the apparent unwillingness

212 Section 4: Focus on Canterbury of the public to alter a tradition of largely because there is considerably less pedestrian unrestricted access for themselves and their traffi c than elsewhere on the Christchurch pets. Effective pest control is also limited by coast. However, the dotterel eggs and chicks the present access regime and public attitudes are highly vulnerable to passing vehicles. to poisoning and trapping. At Southshore Spit, Signs have been erected advising the public the principal challenge for management is to of the presence of nesting dotterel and with sell the concept of a coastal dune mainland markers directing traffi c away from nests island within the Christchurch urban area to the during the season. public and politicians. A comprehensive habitat restoration programme BROOKLANDS SPIT is necessary to re-establish the indigenous Brooklands Spit, the northernmost section of coastal dune ecology of Brooklands Spit. This the Christchurch City coastline, is isolated from will necessitate the progressive removal of urban and farm land by public land at Bottle exotic marram, lupins and pines, and their Lake Forest Park and Spenser Park Beach, replacement with more open native vegetation as well as Brooklands Lagoon. The spit is (pīngao and associated species) that can vested in the Canterbury Regional Council, still effectively bind the sand dunes. The re- refl ecting past river works by the old Catchment establishment of this native dune vegetation will Board. However, most beach management greatly increase the nesting habitat for dotterels is by Christchurch City in association with and other bird species such as white-fronted management of Spenser Park and Bottle Lake terns, Caspian terns, variable oystercatcher, beaches. The spit separates the sea from white-fl ippered penguins (could also use Brooklands Lagoon. The importance of this nesting boxes) and black-billed gulls that estuarine area for Christchurch’s wildlife is previously nested on the Christchurch coastal second only to the Avon-Heathcote Estuary. dunes. Intensive predator trapping and pest control will need to be part of the programme; The spit’s isolation means it has relatively low erecting a fence at the southern end of the levels of human use. Approved vehicles are Spit may well be the most effective means of allowed to drive along this section of beach achieving sustained control. The geography of seaward of the dunes, under a permit system. Brooklands Spit is favourable for integrated pest Almost all traffi c along the beach is to access management while the area’s isolation lessens the south side of the Waimakariri River mouth the problems associated with pest control on for fi shing. Brookland Spit dune vegetation is Southshore Spit. now dominated by exotic plant species — dense marram grassland with scattered lupins, and Better management of people, dogs and pine trees — and as such is not suitable habitat vehicles will also be required. Changes for native dune wildlife. No native planting to the access policy such as no dogs has been carried out here. Extensive tracts of and, for permitted vehicles, to travel only indigenous wetland vegetation occur along the below the high tide mark could be made inland (lagoon) edge of the spit, however. conditions of entry. A restored indigenous dune system at Brooklands Spit would form At times fl ocks of terns, gulls, waders and a natural ecological sequence with other cormorants will roost on the open sand fl ats valuable areas of native habitat, Brooklands near the mouth of the Waimakariri River but, Lagoon and the Waimakariri River, on the as at Southshore, these roosting colonies are northern boundary of Christchurch City. The continually disturbed by people, dogs and management challenge here is twofold: fi rst, vehicles. In recent years, several pairs of as at Southshore, gaining public support for banded dotterel have nested along Brooklands restrictions on public access in order to better Spit in the narrow strip of suitable habitat protect wildlife; second, to obtain resourcing between the high tide mark and the dunes. for a comprehensive programme of habitat The dotterel are probably able to nest here restoration and pest control.

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ACKNOWLEDGEMENTS REFERENCES The excellent Christchurch City Council Christchurch City Council (CCC) 1995: publication Resource Information for the Christchurch beaches and coastal parks Christchurch Coastal Zone, in which a number management plan. Christchurch City Council. of contributors collated an enormous range of (Unnumbered). information, provided much of the information Christchurch City Council (CCC) 2000: for this paper. Andrew Crossland from the Resource information for the Christchurch City Council’s Parks and Waterways Unit gave coastal zone. Parks and Waterways Unit, freely of his time and ideas in useful discussion, Christchurch City Council. 171 p. and offered photographs of birds and coastal Clifton, N. 1979: Effect of Ammophila arenaria habitats. Rodney Chambers, also of the Parks and Desmoschoenus spiralis on foredune and Waterways Unit, provided feedback on an profi le at Ellesmere Spit. Unpublished report, early draft. The katipō spider photograph is Department of Geography, University of courtesy of James Griffi ths. Justin Cope and Canterbury. 14 p. Brodie Young, Environment Canterbury coastal Cope, J.; Flatman, M.; Howes, A.; Young, scientists, also provided photographs and B. 1998: A summary of monitoring and answered technical questions. investigations on the Pegasus Bay coastline, 1993–97. Canterbury Regional Council Technical Report No. U98/30. 49 p. Courtney, S. P. 1983: Aspects of the ecology of Desmoschoenus spiralis (A.Rich.) Hook.f. Unpublished MSc thesis, University of Canterbury, Christchurch, New Zealand. 237 p.

214 Section 4: Focus on Canterbury

Fig. 1 Dune system adjoining the Christchurch urban area managed primarily for coastal protection. Note the constrained width of the dune, the sand-trap fences and planting for dune stabilisation. (Photo: B. Young).

Fig. 2 Steep-sided, densely-vegetated marram Fig. 3 Pīngao dunes at Kaitorete Spit. Pīngao dunes typical of northern Christchurch beaches was previously the dominant foredune species at and north Pegasus Bay. Any native bird nesting is Christchurch and north Pegasus Bay. The dune confi ned to the narrow zone of open sand between form is typically lower and wider than is the case for the high tide fl otsam and base of the foredunes, marram dunes. There also remain extensive areas where nests are vulnerable to passing vehicles. of bare sand between the pīngao clumps, where (Photo: B. Young). native birds can nest. (Photo: B. Young).

215 Section 4: Focus on Canterbury

Fig. 4 Dense low-statured mānuka and harakeke/ Fig. 5 Katipō spider, endemic to New Zealand coastal fl ax scrub vegetation was widespread across the dunes and previously abundant on the Christchurch Christchurch coast backdunes before European beaches. A documented massive population decline settlement. None exists here today; this example is on the Christchurch coast is attributed to habitat loss/ from Farewell Spit, at the north-west tip of the South modifi cation. (Photo: J. Griffi ths). Island. (Photo: A. Crossland).

Fig. 6 Variable oystercatchers have begun nesting Fig. 7 Banded dotterel, a threatened species, have again in north Pegasus Bay in recent years. They recently begun nesting on Brooklands Spit. (Photo: could also return to the Christchurch coast given A. Crossland). some habitat restoration and protection from human disturbance. (Photo: A. Crossland).

Fig. 8 White-fronted terns roosting at Southshore Spit. These and other species of gull, tern and wading birds used to nest on the Christchurch coast in large numbers. (Photo: A. Crossland).

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