Natural and Critical Habitat Assessment (Part 9 of 9)

Environmental Impact Assessment

Project Number: 52111-001 February 2020

Samoa: Alaoa Multi-purpose Dam Project

Volume 2: Alaoa Multipurpose Dam, Upolo, Samoa: Natural and Critical Habitat Assessment (Part 9 of 9)

Prepared by the Electric Power Corporation of Samoa for the Asian Development Bank.

This environmental impact assessment is a document of the borrower. The views expressed herein do not necessarily represent those of ADB's Board of Directors, Management, or staff, and may be preliminary in nature. Your attention is directed to the “terms of use” section on ADB’s website.

In preparing any country program or strategy, financing any project, or by making any designation of or reference to a particular territory or geographic area in this document, the Asian Development Bank does not intend to make any judgments as to the legal or other status of any territory or area.

Alaoa Multipurpose Dam, Upolo, Samoa: Natural and Critical Habitat Assessment

Drafted for the Electric Power Corporation of Samoa by John Pilgrim Limited, with support from the Asian Development Bank

Table of Contents

1 Executive Summary 1 2 Introduction 3 2.1 Purpose and objectives 3 2.2 Approach 3 2.3 Key information gaps 3 3 Biodiversity 4 3.1 Context 4 3.2 Priority biodiversity 4 4 Potential impacts on Critical and Natural Habitat 2 4.1 Potential impacts on terrestrial Critical Habitat 3 4.2 Potential impacts on aquatic Critical Habitat 18 4.3 Potential impacts on Natural Habitat 18 5 Mitigation and conservation measures for impacts on Critical and Natural Habitat 19 5.1 Mitigation and management measures 19 5.2 Residual impacts 21 5.3 No net loss/net gain approach 21 6 Biodiversity monitoring 25 7 References i Appendix A. Critical and Natural Habitat Assessment iv A.1 Areas of analysis iv A.2 Assessment of biodiversity which may qualify the area as Critical Habitat iv A.3 Assessment of Natural Habitat x

1 Executive Summary This document is for the Alaoa multipurpose dam (hereafter “the Project”), c.5 km south of Apia in the Vaisigano River watershed, Upolo, Samoa. It is a supporting document to the Project Environmental Impact Assessment in development (citation to the EIA). The Project is under consideration for financing by the Asian Development Bank (ADB). This draft Natural and Critical Habitat Assessment (NCHA) has been developed to align the Project with ADB biodiversity safeguards (ADB 2009). There is limited information on the status, distribution and ecology of biodiversity in the Project watershed, so this NCHA has taken a precautionary approach. It is a preliminary document and so will be adapted during the Project life in response to new information on the scale or significance of Project impacts or outcomes from mitigation and offsets. The Project footprint overlaps a mosaic of Natural and Modified Habitat, comprising secondary forest – including non-native species – and mixed subsistence farming. More broadly, the Project is on the edge of a large forested landscape. Downstream rivers have been degraded by cumulative impacts from existing weirs, but upstream rivers remain mostly Natural Habitat. A full Critical Habitat Assessment (Appendix A) identified this landscape to be possible or actual Critical Habitat for: one globally Critically Endangered and one Endangered bird (Tooth- billed Pigeon and Mao); two Endangered lizards (Olive Small-scaled Skink and Samoa Skink); three Least Concern, one Data Deficient and one Not Evaluated fish species (Fat-snout Goby, Stenogobius genivittatus, Green Riffle Goby, Stiphodon hydroreibatus, and Schismatogobius tuimanua); an Endangered snail (Thaumatodon hystricelloides); one Critically Endangered and one Endangered palm (Drymophloeus samoensis and Clinostigma samoense); and the Apia Catchments Key Biodiversity Area (Table 1; Section 3). Without mitigation, the Project could have high impacts on some of this Critical Habitat- qualifying biodiversity owing to forest loss and introduction, spread of invasive alien species, and/or prevention of migration of fish above the dam (Section 4). Additional risks are direct degradation of forest and river habitats, displacement of existing agriculture in the Project area, disturbance of birds during construction, hunting of birds by construction workers, and Project-induced access leading to increased longer-term hunting and forest loss/degradation. This NCHA is a supporting document to an Environmental Impact Assessment (citation to the EIA), which will contain standard and general mitigation measures. This NCHA contains mitigation and management measures (Section 5) necessary to reduce residual impacts on Critical Habitat-qualifying biodiversity to levels in line with the ADB Safeguard Policy Statement (ADB 2009). These are anticipated to cost c.US$50,000 (Section 5.1). Particularly key mitigation measures, because of their importance in reducing the most significant impacts, are: • Implement a strict code of conduct forbidding hunting/trapping, and purchase of wildlife, with heavy penalties. Train all personnel on this code of conduct, and its justification (Section 5.1.1); • Install staffed access control on new roads, allowing access to no-one except operational staff, or government officials (Section 5.1.2); • Engage and educate the local community, including providing incentives to conserve priority biodiversity - such as employment in restoration, invasive species control and monitoring (Section 5.1.3); and • Take care to avoid introduction of new invasive species to, and spread of existing invasive species within, the Project area (Section 5.1.4). Other specific mitigation measures comprise: • Prior to finalization of project designs and any clearance, identify, clearly mark and map all mature native trees, to facilitate avoidance and minimization (Section 5.1.5); • Minimize clearance of native vegetation at the Project site and around associated roads and other infrastructure; using already cleared or modified areas for construction wherever possible. Prioritize avoidance of Ficus and Dysoxylum trees (which may provide seasonal food sources

for Tooth-billed Pigeon), and attempt to relocate any of these which cannot be avoided (Section 5.1.6); • Replant native vegetation (including Dysoxylum species) in any temporarily disturbed areas (Section 5.1.7); • Regularly maintain and inspect/certificate all vehicles, equipment and machinery to ensure that noise levels conform to national standards (Section 5.1.8); • Avoid construction during the most sensitive Mao breeding period (June-August inclusive) (Section 5.1.9); • Avoid construction within 150 m of an occupied Tooth-billed Pigeon or Mao nest (Section 5.1.10); • Educate local people on the dangers of deliberate introductions of invasive species (Section 5.1.11). After these mitigation measures, the Project is predicted to reach no net loss for most Critical Habitat-qualifying biodiversity. However, some residual impacts on this priority biodiversity are expected to remain measurable by the Project operations phase, particularly direct loss of terrestrial and aquatic habitat, and degradation of upstream habitats by prevention of aquatic species’ migration past the dam, but also downstream degradation of aquatic habitat and fragmentation of terrestrial habitat owing to the Project roads and reservoir (Section 5.2). Given these residual impacts, and the wider context of substantial cumulative impacts on forests and forest-dwelling species in Samoa, and on rivers and aquatic life in the Vaisigano watershed, the Project is also planning to make a positive contribution that will offset these residual impacts (Section 5.3). This will achieve a net gain for biodiversity in alignment with ADB safeguard requirements for projects in areas of Critical Habitat (ADB 2009). Specifically, it aims to restore up to 240 ha of forest elsewhere in the Vaisigano River watershed (which will also support the Project’s flood control goals) and to control key invasive species in those areas (at a cost of c.US$155,000-320,000/year), to establish appropriate environmental flows from existing weirs in the watershed in order to facilitate aquatic species’ migration and improve river quality (COST ESTIMATE?), and to support translocation of some Mao to American Samoa (at a cost of c.US$250,000). In total, costs of a net gain approach are thus estimated to be c.US$4.2-8.3 million (Section 5.1). To ensure Project mitigation is successfully implemented and impacts avoided or minimized, the Project will undertake a program of monitoring and evaluation (Section 6), which will proceed into the operational life of the Project in cases where there is a risk of long-term residual impacts. In summary, this Project will be compliant with ADB biodiversity safeguards (ADB 2009) because it is not located within a legally protected area and will put in place mitigation (Section 5.1) and offsets (Section 5.3) to address impacts on Natural and Critical Habitat that result in: (i) no measurable adverse impacts on critical habitat that could impair its ability to function; (ii) no reduction in the population of any recognized endangered or critically endangered species; and (iii) overall benefits substantially outweighing the environmental costs. The mitigation and monitoring approaches summarized in this document will be integrated into a set of Biodiversity Management and Monitoring Plans for groups of terrestrial biodiversity (e.g., aquatic species, birds and bats, etc.). The no net loss/net gain approach will be developed into a detailed Biodiversity Offset Plan (covering terrestrial, aquatic, policy and institutional support).

2 Introduction 1.1 2.1 Purpose and objectives This document is a Natural and Critical Habitat Assessment (NCHA) for the Alaoa multipurpose dam (hereafter “the Project”), south of Apia, in Upolo, Samoa. The dam is primarily intended for flood control and water supply, but also includes small-scale hydropower generation to increase Project financial viability. The Project comprises a c.60 m-high dam, 20 ha reservoir (at full flood level), a penstock pipe, small power station, and associated roads. For construction, quarries, an aggregate crushing plant, a batching plant, project site office and stock piles have also been proposed. The Project is under consideration for financing by the Asian Development Bank (ADB). Under the ADB Safeguard Policy Statement (SPS: ADB 2009), this has been identified as a Category A project. This NCHA is a supporting document to an Environmental Impact Assessment in development (citation to the EIA). The ADB SPS requires projects in Natural Habitat to design mitigation measures to achieve at least no net loss of biodiversity. It requires projects in Critical Habitat to demonstrate ‘no measurable adverse impacts, or likelihood of such, on the critical habitat which could impair its high biodiversity value or the ability to function’, no ‘reduction in the population of any recognized endangered or critically endangered species or a loss in area of the habitat concerned such that the persistence of a viable and representative host ecosystem be compromised’, and mitigation of any lesser impacts. This NCHA assesses these risks and presents the Project’s strategy for alignment with the ADB SPS. Following the draft ADB Environmental Safeguards Good Practice Sourcebook (ADB 2012), this NCHA assesses the presence of Critical and Natural Habitat in the Project area (Section 3; Appendix A), evaluates potential impacts on priority biodiversity (Section 4), outlines Project commitments to mitigation and management measures to achieve at least no net loss for Critical and Natural Habitat (Section 5), and outlines an approach to monitoring and evaluation to give assurance of Project performance (Section 6). It is a preliminary document and so actions herein will be adapted during the Project life in response to any new information on the scale or significance of Project impacts or outcomes from mitigation and offsets. 1.2 2.2 Approach This NCHA was developed through a review of existing Project documentation, other existing grey and published literature, and consultations with authors of Project documentation. It aligns with the ADB SPS (ADB 2009) and International Finance Corporation Performance Standard 6 and its accompanying Guidance Note (IFC 2012, 2019). Except where necessary, this document does not repeat extensive information available in other key Project documents, such as the baseline bird and bat, aquatic, or invertebrate surveys. 1.3 2.3 Key information gaps Although there have been detailed – if rapid – surveys for birds and bats (Stirnemann & Taylor- Smith 2019), invertebrates (Wildland 2019) and aquatic species (Entura 2019a) upstream and downstream from the Project area, there is limited recent information on the status, distribution and ecology of plants in this area, or in all biodiversity in the broader area within which the Project is located. Likewise, no fine-scale vegetation maps exist, and so it is currently challenging to distinguish largely native forest (Natural Habitat) from forest largely comprised of invasive species (Modified Habitat). Further, no surveys have yet quantitatively estimated the current quality of terrestrial or aquatic habitats (although aquatic habitat quality has been estimated on the basis of considerable survey work). This NCHA has thus been developed on a precautionary basis, assuming – where there is doubt – that species may be present in the Project area and may be affected by the Project, that all forest is Natural Habitat, and with estimates of terrestrial and aquatic habitat quality estimated on the basis of expert opinion rather than measurable criteria.

3 Biodiversity 1.4 3.1 Context Samoa was originally almost entirely covered in tropical rain forest, but less than 20% of original habitat now remains (Male 2019). Together with American Samoa, the archipelago has high levels of endemism – e.g., around a quarter of flowering plants are endemic, and over 80% of birds represent endemic species or subspecies. Many endemic species are now threatened as a result of habitat loss, which exacerbates the natural action of cyclones and facilitates the spread of alien invasive species. Few protected areas exist, and those that do are severely under-resourced. The Project is on the edge of the largest remaining area of forest in Upolo, Samoa’s second largest remaining forest block. Aquatic ecosystems in the watershed have been extensively modified owing to water regulation and extraction. 1.5 3.2 Priority biodiversity On a precautionary basis, a full Critical Habitat Assessment (Appendix A) identified the landscape within which the Project is situated to be likely or actual Critical Habitat for: one globally Critically Endangered and one Endangered bird; two Endangered lizards; three Least Concern, one Data Deficient and one Not Evaluated fish species; an Endangered snail; one Critically Endangered and one Endangered palm; and one internationally-recognized area (Table 1). Some uncertainty remains in the conclusions of this assessment, given limited information on the fine-scale distribution of many of these species in Upolo. Nonetheless, this uncertainty will not change the overall conclusions of this assessment. Although in some cases conclusions could be refined by further studies, on a precautionary basis the features listed in Table 1 are all be considered priority biodiversity for the Project to avoid, mitigate and – where necessary – offset impacts upon. Following this table are a set of brief profiles for Critical Habitat-qualifying biodiversity, focusing on where and when each is likely to occur in the Project area. More extensive details of why each feature meets Critical Habitat criteria are given in Appendix A. The Project is situated in a mosaic of Natural and Modified Habitat, both terrestrial and freshwater. Remaining forest may be heavily impacted in places, particularly by the spread of invasive species, but mostly retains primary ecological functions and is of value to a number of priority species. Given the prevalence of non-native tree species which are difficult to identify from remotely sensed imagery, on a precautionary basis all forest is currently considered Natural Habitat, and non-forest areas Modified Habitat (Appendix A.3). Data on many individual species’ distributions across the area are sufficiently sparse to preclude detailed mapping of Critical Habitat. On a precautionary basis, it is therefore assumed that all terrestrial Natural Habitat, and any terrestrial Modified Habitat with remaining mature trees, may also qualify as Critical Habitat. Figure 1 summarizes the location of aquatic Critical, Natural and Modified Habitat in the Vaisigano watershed, based on Entura (2019a).

Table 1. Summary of Critical Habitat-qualifying biodiversity in the Project area Biodiversity Biodiversity Critical Habitat Justification Present in Project type criterion qualified Project impacts? 1 2 3 4 5 6 impact area? (Section 4) Bird Tooth-billed Pigeon X Terrestrial Area of Assessment (AoA) supports more than 0.5% of the population, Likely Likely Didunculus strigirostris and five pairs, of this globally Critically Endangered bird. (seasonally) Bird Mao Gymnomyza X Found during Project baseline surveys, including indications of breeding in/near the Yes Yes samoensis Project site. Terrestrial AoA supports more than 0.5% of the population, and five pairs, of this globally Endangered bird. Reptile Olive Small-scaled X On a precautionary basis, it is possible that the terrestrial AoA holds more than 0.5% Possibly Potentially Skink Emoia lawesi of the global population of this globally Endangered lizard. Reptile Samoa Skink Emoia X On a precautionary basis, it is possible that the terrestrial AoA holds more than 0.5% Possibly Potentially samoensis of the global population of this globally Endangered lizard. Fish Schismatogobius X X The aquatic Aoa is likely to hold more than 1%, and possibly 10%, of this recently- Yes Potentially tuimanua described restricted-range fish (not yet evaluated on the IUCN Red List). (downstream) Fish Fat-snout Goby X On a precautionary basis, it is possible that the aquatic AoA holds more than 1% of Yes Yes (Sicyopterus pugnans) the global population of this globally Least Concern fish. Fish Stenogobius X On a precautionary basis, it is possible that the aquatic AoA holds more than 1% of Yes Potentially genivittatus the global population of this globally Least Concern fish. (downstream) Fish Green Riffle Goby X On a precautionary basis, it is possible that the aquatic AoA holds more than 1% of Yes Yes (Stiphodon elegans) the global population of this globally Least Concern fish. Fish Stiphodon X On a precautionary basis, it is possible that the aquatic AoA holds more than 1% of Yes Yes hydroreibatus the global population of this globally Data Deficient fish. Snail Thaumatodon X On a precautionary basis, it is possible that the terrestrial AoA holds more than 0.5% Possibly Unlikely hystricelloides of the global population of this globally Endangered snail. Plant Drymophloeus X On a precautionary basis, it is possible that the terrestrial AoA holds more than 0.5% Possibly Unlikely samoensis of the global population of this globally Critically Endangered palm. Plant Clinostigma X On a precautionary basis, it is possible that the terrestrial AoA holds more than 0.5% Possibly Potentially samoense of the global population of this globally Endangered palm. Internationally Apia Catchments Key X Area of high biodiversity value, internationally recognized as an Important Bird Area Overlapping Yes recognized area Biodiversity Area and Key Biodiversity Area.

Figure 1. Schematic of aquatic Area of Analysis, showing areas of Critical, Natural and Modified Habitat, and any Critical Habitat-qualifying fish species present in each stretch

Tooth-billed Pigeon (Didunculus strigirostris) More information is available here and in Stirnemann & Taylor-Smith (2019). This bird, also known as Manumea, is considered globally Critically Endangered (BirdLife International 2018), owing to habitat loss, habitat degradation and predation by invasive species, cyclone damage (exacerbated by habitat loss and invasive plants), and hunting. It is endemic to Samoa and has been seen near the Project site (Stirnemann & Taylor-Smith 2019). The species moves seasonally in response to food availability, feeding particularly on the fruit of Dysoxylum trees. When these trees are in fruit, pigeons will seek them out – whether the trees are within forest or isolated in otherwise-cleared “plantation” areas (Rebecca Stirnemann pers. comm. 2019). It is thus likely that the species occurs seasonally in the Project area. The species is more likely to nest in high quality forest, but its breeding ecology is poorly known so it is possible that it also nests near the Project.

Mao (Gymnomyza samoensis) More information is available here and in Stirnemann & Taylor-Smith (2019).

This bird is considered globally Endangered (BirdLife International 2016), owing to habitat loss, habitat degradation and predation by invasive species, and cyclone damage (exacerbated by habitat loss and invasive plants). It is endemic to foothill and upland forest on Samoa, and has territories overlapping and surrounding the Project footprint (Stirnemann & Taylor-Smith 2019). The species is territorial, and breeds from April to November inclusive. It feeds on nectar, fruit and insects, but is particularly reliant on large trees for their flowers and epiphytic mistletoe that they support.

Olive Small-scaled Skink (Emoia lawesi) More information is available here. This lizard is considered globally Endangered (Allison & Austin 2010), owing to habitat loss and predation by invasive species. It occurs in forests of Samoa, American Samoa, Niue and Tonga, and is likely to occur in the Project area. The species is poorly-known, but believed to occur mainly on the ground or in lower-level vegetation (herbs and low shrubs).

Samoa Skink (Emoia samoensis) Photos and more information are available here. This lizard occurs in Samoa and American Samoa and is considered globally Endangered (Allison & Austin 2010). It was formerly common in lowland areas, but has been extirpated from many areas as a result of invasion by Yellow Crazy Ants (Paratrechina longicornis). It is an arboreal species, though mainly found within several meters of the ground. The species is presumed to occur in the Project area.

Schismatogobius tuimanua More information is available here and in Entura (2019a). This rare, recently-described goby has not yet been assessed on the IUCN Red List. It is known from Samoa and American Samoa, and considered restricted-range. It was found in the lower reaches of the Vaisigano River during recent baseline surveys (William Elvey in litt. 2019). It is amphidromous, meaning that it migrates from freshwater to the sea. Based on current knowledge, however, this fish is unlikely to occur further upstream, in the Project area – though it may be affected by any downstream impacts.

Fat-snout Goby (Sicyopterus pugnans) More information is available here and in Entura (2019a). This fish is known from Samoa and French Polynesia and is not considered globally threatened (Boseto 2012a). It prefers to inhabit deeper areas of streams over rock substrate. It is amphidromous, meaning that it migrates from freshwater to the sea, and can climb over significant obstacles during this migration. As such, baseline surveys found this species from downstream of the Samasoni weir up to the reaches that are within the proposed inundation zone for the new reservoir (Entura 2019). This species is also likely to occur in the reaches upstream of the proposed reservoir.

Stenogobius genivittatus More information is available here and in Entura (2019a). This fish is known from Samoa, French Polynesia and the Cook Islands, and is not considered globally threatened (Hoese 2012b). It occurs in the lower reaches of rivers and is amphidromous, meaning that it migrates from freshwater to the sea. Owing to current obstacles in the river and this species’ inability to climb, baseline surveys only found this species downstream of the Samasoni weir and downstream of the first significant waterfall (Entura 2019a), distant from the proposed Project.

Green Riffle Goby (Stiphodon elegans)

More information is available here and in Entura (2019a). This fish is known from Samoa, Futuna, French Polynesia and the Cook Islands, and is not considered globally threatened (Boseto 2012b). It occurs in the lower reaches of rivers and is amphidromous, meaning that it migrates from freshwater to the sea. It prefers coarse rocky substrates and slow to medium currents in pools, where it feeds on algae (Entura 2019a). It has a weak climbing ability, but baseline surveys found this species both upstream and downstream of the Samasoni weir (Entura 2019a), including in the 1.3 km stretch of river downstream of the proposed Project dam.

Stiphodon hydroreibatus More information is available here and in Entura (2019a). This fish is known from Samoa, American Samoa and Futuna and is considered globally Data Deficient (Boseto 2012c). It feeds on algae in the lower and mid reaches of rivers, up to at least 200 m altitude, in slow-flowing habitats with pebbles and larger substrate. It is amphidromous, meaning that it migrates from freshwater to the sea, and can climb over significant obstacles during this migration. It was recorded upstream of the Samasoni weir, including to the existing Alaoa dam intake (Entura 2019a), and presumably also occurs downstream of the Samasoni weir at least seasonally.

Thaumatodon hystricelloides Pictures and more information are available in Cowie et al. (2017). This terrestrial snail is tiny (several millimeters across) and now only known from high elevations on Upolo (Cowie et al. 2017), including the Project’s terrestrial AoA. It is considered globally Endangered (Mollusc Specialist Group 1996). The species is poorly-known so it is possible, though probably unlikely, that it occurs close to Project infrastructure.

Drymophloeus samoensis More information is available here. This palm only occurs in montane cloud forest on Upolo and Savai’i and is considered globally Critically Endangered (Whistler & Johnson 1998b). Given its altitudinal preferences, it is unlikely that this species occurs close to Project infrastructure.

Clinostigma samoense More information is available here. This palm is restricted to lowland forests in Upolo and is considered globally Endangered, owing to habitat loss (Whistler & Johnson 1998a). Given its altitudinal preferences, this species may occur in the Project area.

Apia Catchments Key Biodiversity Area More information is available here. The internationally recognized Apia Catchments Important Bird Area (also de facto a Key Biodiversity Area) overlaps the Project. This IBA is of particular importance for Tooth-billed Pigeon and Mao (see above). The boundaries of this IBA appear to be loosely based on a large area of remaining forest.

4 Potential impacts on Critical and Natural Habitat This assessment followed recent good practice impact assessment methodology used for a project involving aquatic and terrestrial impacts (MRDI 2019). Following this methodology, pre-mitigation impacts on Critical Habitat (Table 1) are assessed in Table 2 and discussed in Sections 4.1 and 4.2. Impacts on Natural Habitat are discussed in Section 4.3.

1.6 4.1 Potential impacts on terrestrial Critical Habitat The Project’s terrestrial AoA represents likely or actual Critical Habitat for two birds; two lizards; a snail; two palms; and one internationally-recognized area (Table 1). The magnitude of risks to this Critical Habitat-qualifying biodiversity ranges from Minor-Major, given their rarity, threatened status, conservation importance, and level of public concern about these species and sites (Table 2). The overall significance of potential impacts on Critical Habitat is assessed as Low-High (Table 2). Approximately 24.4 ha of vegetation clearance will be necessary for dam construction, plus additional clearance for roads and other infrastructure (Stirnemann & Taylor-Smith 2019). Vegetation clearance is considered a Medium significance impact for all terrestrial priority biodiversity. Vegetation clearance will also result in a level of forest fragmentation and edge effects, which disturb neighboring habitats through changes in wind, sunlight, temperature and dust (Stirnemann & Taylor-Smith 2019; Wildland 2019). These are significant but relatively small scale and likely to develop in the medium term, so are assessed to be a Low significance impact. Construction activities may result in (temporary) disturbance (Stirnemann & Taylor-Smith 2019), for example to breeding birds. Impacts of displacement of species owing to this disturbance are therefore assessed to be of Low significance. The potential for indirect impacts is also of concern. Without mitigation, there is a risk of hunting of wildlife by construction workers and project roads or vegetation clearance may facilitate increased human access, leading to induced rises in hunting, logging, and forest clearance (Stirnemann & Taylor-Smith 2019). Such impacts can be severe, though will be limited in extent for this Project owing to the limited length of new roads planned. These impacts are considered Low for most biodiversity, but – owing to their greater sensitivity – the potential impact of increased longer-term hunting and forest clearance/degradation owing to induced access, is considered of Medium significance for Tooth-billed Pigeon and Mao. Project infrastructure will displace existing agriculture, e.g. in areas mapped as “plantation” by Stirnemann & Taylor-Smith (2019), resulting in another indirect impact. This agriculture is mainly for subsistence, so is likely to move elsewhere, likely nearby – and thus result in more clearance of forest in the Vaisigano catchment. This was quantified by Stirnemann & Taylor- Smith (2019) as 6.6 ha, plus unquantified additional clearance for roads and other infrastructure. These are long-term impacts, so displacement of agriculture is assessed to be a Medium significance impact for all terrestrial priority biodiversity. A potential indirect project impact on Critical Habitat is the introduction of invasive alien species (IAS). The Global Invasive Species Database (http://www.iucngisd.org/gisd) has records for 78 terrestrial or freshwater IAS in Samoa, of which 46 are plants. IAS can spread rapidly once introduced, significantly modifying habitat for forest-dependent species, and present a very high risk to biodiversity globally. Roads, vegetation clearance, soil disturbance and establishment of non-natural habitats are also likely to encourage invasive alien species to the Project area (Entura 2019a; Stirnemann & Taylor-Smith 2019; Wildland 2019). There is potential for construction machinery, equipment or materials to introduce IAS to forested areas within the Project site, particularly plants – e.g., as seeds within soil on machinery. Invasive alien plants degrade native forest, reducing habitat quality for most native plant and animal species. Invasive alien species can also directly kill native species – e.g., rat and cat predation is a significant threat to both priority bird species identified in the Project area, and species of climbing vine such as fue lautetele (Merremia species) and fue saina (Mikania micrantha) can smother native vegetation (Wildland 2019). On a precautionary basis, the potential impact on terrestrial Critical Habitat of introduction/spread of invasive alien species is considered of High significance.

Table 2. Impact assessment for Critical Habitat-qualifying biodiversity in the Project area (refer to MRDI 2019 for Impact Significance

Rating Methodology)

Environmental Component Aspect Phase Project Impact Sensitivityof Receptors of Level Public Concern Severity or degree of changeto the receptor Magnitude Timeframe Scale Spatial Consequence Probability Significanc P, C Vegetation clearance. L M L MIN LT SMALL M DEFINITE M Edge effects and habitat fragmentation P, C L M L MIN LT SMALL M DEFINITE M resulting from vegetation clearance. Displacement of agriculture, resulting in P, C L M L MIN LT SMALL M POSS M vegetation clearance elsewhere. Apia Catchments Key Vegetation Forest clearance/degradation, owing to Biodiversity Area cover O L M L MIN MT SMALL L POSS L induced access for people via project roads.

Introduction/spread of invasive alien P, C L M M MOD LT INTER H POSS H species.

P, C Vegetation clearance. H H L MOD LT SMALL M DEFINITE M

Edge effects and habitat fragmentation P, C L M L MIN LT SMALL M DEFINITE M resulting from vegetation clearance. Displacement of agriculture, resulting in Habitat P, C L M L MIN LT SMALL M POSS M vegetation clearance elsewhere. Forest clearance/degradation, owing to O L M M MOD LT SMALL M POSSIBLE M Tooth-billed Pigeon induced access for people via project roads. (Didunculus strigirostris) Introduction/spread of invasive alien P, C H H M MAJ LT INTER H POSSIBLE H and Mao (Gymnomyza species. samoensis) Displacement of species due to noise, Distribution P, C presence of machinery and equipment and L M L MIN ST SMALL L POSSIBLE L presence of staff. Introduction/spread of invasive alien species P, C, O H H H MAJ LT INTER H POSSIBLE H (causing predation/smothering). Mortality C Hunting by construction workers. H H L MOD ST SMALL L POSSIBLE L Induced access for hunters via project O H M L MOD MT SMALL M POSSIBLE M roads. Olive Small-scaled Skink P, C Vegetation clearance. H L L MIN LT SMALL M DEFINITE M (Emoia lawesi), Samoa Edge effects and habitat fragmentation P, C L M L MIN LT SMALL M DEFINITE M Skink (Emoia Habitat resulting from vegetation clearance. samoensis), Displacement of agriculture, resulting in P, C L M L MIN LT SMALL M POSS M Thaumatodon vegetation clearance elsewhere.

Environmental Component Aspect Phase Project Impact Sensitivityof Receptors of Level Public Concern Severity or degree of changeto the receptor Magnitude Timeframe Scale Spatial Consequence Probability Significanc hystricelloides, Forest clearance/degradation, owing to O M L L MIN MT SMALL L POSSIBLE L Drymophloeus induced access for people via project roads. samoensis and Introduction/spread of invasive alien Clinostigma samoense P, C H L M MOD LT INTER H POSSIBLE H species.

Introduction/spread of invasive alien species Mortality P, C, O H L H MOD LT INTER H POSSIBLE H (causing predation/smothering).

C, O Loss of habitat in the reservoir. H L L MOD LT SMALL M DEFINITE M

Fat-snout Goby Prevention of species' migration upstream (Sicyopterus pugnans) C, O of the western branch confluence (habitat H L M MOD LT INTER H DEFINITE H Habitat and Stiphodon loss). Degradation by flow regulation and reduced hydroreibatus C, O L L L MIN MT SMALL L POSSIBLE L downstream water quality. Introduction/spread of invasive alien P, C M L L MIN LT INTER M POSSIBLE M species. Prevention of species' migration upstream C, O of the western branch confluence (habitat H L M MOD LT INTER H DEFINITE H loss). Green Riffle Goby Habitat Degradation by flow regulation and reduced (Stiphodon elegans) C, O L L L MIN MT SMALL L POSSIBLE L downstream water quality. Introduction/spread of invasive alien P, C M L L MIN LT INTER M POSSIBLE M species. Degradation by flow regulation and reduced Schismatogobius C, O L L L MIN MT INTER L POSSIBLE L downstream water quality. tuimanua and Habitat Introduction/spread of invasive alien Stenogobius genivittatus P, C M L L MIN LT INTER M POSSIBLE M species. Prevention of species' migration upstream C, O L M L MIN LT SMALL M DEFINITE M of the western branch confluence. Aquatic Natural Habitat Habitat Introduction/spread of invasive alien P, C L L M MIN LT SMALL M POSSIBLE M species.

Notes: Project Phase = P-Preparation, C-Construction, WC-Worksheet Closure, O-Operation; Magnitude = MAJ-Major, MOD-Moderate, MIN- Minor; Timeframe = LT-Long-term, MT-Medium-term, ST-Short-term; Spatial Scale = INTER-Intermediate, SMALL-Small; Probability = DEF- Definite, POSS-Possible, UNLIKE-Unlikely.

1.7 4.2 Potential impacts on aquatic Critical Habitat The Project’s aquatic AoA represents likely or actual Critical Habitat for five fishes (Table 1; Figure 1). The magnitude of risks to this Critical Habitat-qualifying biodiversity ranges from Minor-Moderate, given their rarity, threatened status, conservation importance, and level of public concern about these species and sites (Table 2). Some direct habitat loss will occur, as a result of flooding by the reservoir of c.1.3 km of the middle-east branch of the Vaisigano River (an additional 1 km of the east branch will be flooded, but is already Modified Habitat). Direct loss of river habitats is considered a Medium significance impact to Fat-snout Goby, Green Riffle Goby, and Stiphodon hydroreibatus. The dam design will prevent migration of fish and crustaceans, resulting in the loss of these species in the east and middle-east branches of the Vaisigano River (Entura 2019a). These species are a significant component of these river stretches, and their loss would effectively degrade the quality of the remaining aquatic habitat. This impact will affect the unflooded 12.7 km of the east branch and 11.4 km of the middle-east branch, though only 8.2 km of the east branch might currently be considered Natural Habitat owing to existing offtake for the Fale ole Fee scheme (Entura 2019a). This impact will also necessarily affect a 1.2 km stretch of river directly downstream from the new dam, since migration into this stretch will be discouraged by an in-river structure in order to avoid an ecological sink (Entura 2019a,b; Jean Williams, ADB, in litt. 2019). Given climbing abilities of the migratory fish in this river, this structure may take the form of a high velocity chute (e.g., Hoover et al. 2003). Prevention of species’ migration upstream of the western branch confluence is considered a High significance impact for Fat-snout Goby, Green Riffle Goby and Stiphodon hydroreibatus, the Critical Habitat-qualifying species found this far upstream. Although this is a significant impact, it is considered substantially lower than the potential impact of these species migrating upriver of the western branch confluence into an ecological trap at the base of the Project dam. The operation of the dam’s reservoir will regulate flows and may lower water quality downstream, both of which may degrade aquatic environments to a limited degree (Entura 2019a). Given the limited likely degradation from this Project, and existing cumulative downstream impacts, degradation in downstream river habitat quality through flow regulation and reduced water quality is assessed to be of Low significance. As for terrestrial habitats, a potential indirect project impact on aquatic Natural Habitat is the introduction of invasive alien species (IAS). Establishment of non-natural habitats (such as the reservoir) are likely to encourage invasive alien aquatic species to the Project area (Entura 2019a). Of particular concern are Water Hyacinth (Eichhornia crassipes), tilapia (Oreochromis mossambicus) and mosquito fish (Gambusia affinis) (Entura 2019a). There is potential for construction machinery, equipment or materials to introduce Water Hyacinth, and all three species are frequently deliberately introduced by local people. Establishment of Water Hyacinth in a reservoir can degrade downstream rivers, while both tilapia and mosquito fish can outcompete native species and degrade native ecosystems. Considering existing degradation of aquatic habitats, the potential impact of introduction/spread of invasive alien species is considered of Medium significance.

1.8 4.3 Potential impacts on Natural Habitat All terrestrial Natural Habitat is precautionarily treated as Critical Habitat, in the absence of detailed information on the distribution of key species (Section A.3). As a result, impacts on terrestrial Natural Habitat are currently considered to be the same as those on Critical Habitat (Section 4.1). Two areas of non-Critical aquatic Natural Habitat exist in the Vaisigano watershed: the stretch upstream from the middle branch weir, and the east branch stretch upstream of the Fale ole Fee weir (Figure 1). These stretches of river may experience Medium significance impacts

18 from the Project, owing to prevention of aquatic species’ migration upstream and introduction/spread of invasive alien species (see Section 4.2 for more detail on this issue). 2. 5 Mitigation and conservation measures for impacts on Critical and Natural Habitat 2.1 5.1 Mitigation and management measures This NCHA is a supporting document to an Environmental Impact Assessment in development (citation to the EIA), which will contain standard and general mitigation measures. Table 3 summarizes specific mitigation measures relevant to potential Project impacts on Critical Habitat-qualifying biodiversity (Section 4). Together, all mitigation measures will be included in a set of Biodiversity Management and Monitoring Plans for groups of terrestrial biodiversity (e.g., aquatic species, birds and bats, etc.). The specific mitigation measures identified in Table 3 are explained in Sections 5.1.1-5.1.11, and are anticipated to result in limited additional financial costs (c. US$10,000 of capital costs,

Table 3. Mitigation and management measures for Critical Habitat-qualifying biodiversity and Natural Habitat. Responsibility Environmental Project Aspect Impact Mitigation action Development/ Component phase Control implementation Prior to finalization of project designs and any clearance, identify, clearly Detailed design mark and map all mature native trees, to facilitate avoidance and contractor minimisation. Minimize clearance of native vegetation at the Project site and around associated roads and other infrastructure; using already cleared or Detailed design modified areas for construction wherever possible. Prioritize avoidance P, C Vegetation clearance. and civil works of Ficus and Dysoxylum trees (which may provide seasonal food sources contractors for Tooth-billed Pigeon), and attempt to relocate any of these which cannot be avoided.

Replant native vegetation (including Dysoxylum species) in any Civil works

temporarily disturbed areas. contractor

Edge effects and habitat Minimize clearance of native vegetation at the Project site and around Detailed design P, C fragmentation resulting from associated roads and other infrastructure; using already cleared or and civil works vegetation clearance. modified areas for construction wherever possible. contractors Apia Catchments Key Vegetation Biodiversity Area cover Engage and educate the local community, including providing incentives Displacement of agriculture, to conserve priority biodiversity - such as employment in restoration, P, C resulting in vegetation invasive species control and monitoring - prioritising Project-affected clearance elsewhere. people. Install staffed access control on new roads, allowing access to no-one except operational staff, or government officials, and inspecting Forest loss/degradation, departing vehicles for poached wildlife. O owing to induced access for Engage and educate the local community, including providing incentives people via project roads. to conserve priority biodiversity - such as employment in restoration,

invasive species control and monitoring - prioritising Project-affected people. Take care to avoid introduction of new invasive species to, and spread of existing invasive species within, the Project area through: Introduction/spread of - washing of vehicles, equipment and supplies before entry to the Project Civil works P, C invasive alien species. area; contractor - monitoring for invasive species; and - control/eradication of invasive species where found. Prior to finalization of project designs and any clearance, identify, clearly Tooth-billed Pigeon Detailed design Habitat P, C Vegetation clearance. mark and map all mature native trees, to facilitate avoidance and (Didunculus strigirostris) contractor minimisation.

Responsibility Environmental Project Aspect Impact Mitigation action Development/ Component phase Control implementation and Mao (Gymnomyza Minimize clearance of native vegetation at the Project site and around samoensis) associated roads and other infrastructure; using already cleared or Detailed design modified areas for construction wherever possible. Prioritize avoidance and civil works of Ficus and Dysoxylum trees (which may provide seasonal food sources contractors for Tooth-billed Pigeon), and attempt to relocate any of these which cannot be avoided. Avoid any vegetation clearance within 150 meters of an occupied Tooth- Civil works

billed Pigeon or Mao nest. contractor Replant native vegetation (including Dysoxylum species) in any Civil works

temporarily disturbed areas. contractor

Engage and educate the local community, including providing incentives Displacement of agriculture, to conserve priority biodiversity - such as employment in restoration, P, C resulting in vegetation invasive species control and monitoring - prioritising Project-affected clearance elsewhere. people. Install staffed access control on new roads, allowing access to no-one except operational staff, or government officials, and inspecting departing vehicles for poached wildlife. Forest loss/degradation, O owing to induced access for Engage and educate the local community, including providing incentives people via project roads. to conserve priority biodiversity - such as employment in restoration,

invasive species control and monitoring - prioritising Project-affected people.

Take care to avoid introduction of new invasive species to, and spread of existing invasive species within, the Project area through: Introduction/spread of - washing of vehicles, equipment and supplies before entry to the Project Civil works P, C invasive alien species. area; contractor - monitoring for invasive species; and - control/eradication of invasive species where found. Regularly maintain and inspect/certificate all vehicles, equipment and Civil works

Displacement of species due machinery to ensure that noise levels conform to national standards. contractor to noise, presence of Avoid any construction activity during the most sensitive Mao breeding Civil works Distribution P, C machinery and equipment period (June-August inclusive). contractor and presence of staff. Avoid any construction activity within 150 meters of an occupied Tooth- Civil works

billed Pigeon or Mao nest. contractor

invasive species control and monitoring - prioritising Project-affected people. Prior to finalization of project designs and any clearance, identify, clearly Detailed design mark and map all mature native trees, to facilitate avoidance and contractor minimisation. Minimize clearance of native vegetation at the Project site and around Detailed design P, C Vegetation clearance. associated roads and other infrastructure; using already cleared or and civil works modified areas for construction wherever possible. contractors

Replant native vegetation (including Dysoxylum species) in any Civil works

Olive Small-scaled temporarily disturbed areas. contractor Skink (Emoia lawesi), Samoa Skink (Emoia samoensis), Edge effects and habitat Minimize clearance of native vegetation at the Project site and around Detailed design Thaumatodon Habitat P, C fragmentation resulting from associated roads and other infrastructure; using already cleared or and civil works hystricelloides, vegetation clearance. modified areas for construction wherever possible. contractors Drymophloeus samoensis and Engage and educate the local community, including providing incentives Displacement of agriculture, Clinostigma samoense to conserve priority biodiversity - such as employment in restoration, P, C resulting in vegetation invasive species control and monitoring - prioritising Project-affected clearance elsewhere. people. Install staffed access control on new roads, allowing access to no-one

except operational staff, or government officials. Forest loss/degradation, O owing to induced access for Engage and educate the local community, including providing incentives to conserve priority biodiversity - such as employment in restoration, people via project roads. invasive species control and monitoring - prioritising Project-affected people.

Responsibility Environmental Project Aspect Impact Mitigation action Development/ Component phase Control implementation Take care to avoid introduction of new invasive species to, and spread of existing invasive species within, the Project area through: Introduction/spread of - washing of vehicles, equipment and supplies before entry to the Project Civil works P, C invasive alien species. area; contractor - monitoring for invasive species; and - control/eradication of invasive species where found. Take care to avoid introduction of new invasive species to, and spread of Introduction/spread of existing invasive species within, the Project area through: invasive alien species - washing of vehicles, equipment and supplies before entry to the Project Civil works Mortality P, C, O (causing area; contractor predation/smothering). - monitoring for invasive species; and - control/eradication of invasive species where found. Loss of habitat in the C, O None realistic. n/a n/a reservoir. Prevention of species' migration upstream of the C, O None feasible. n/a n/a western branch confluence (habitat loss). Fat-snout Goby C, O Degradation by flow None feasible. n/a n/a (Sicyopterus pugnans) Habitat regulation and reduced and Stiphodon downstream water quality. hydroreibatus Take care to avoid introduction of new invasive species to, and spread of existing invasive species within, the Project area through: Introduction/spread of - washing of vehicles, equipment and supplies before entry to the Project Civil works P, C invasive alien species. area; contractor - monitoring for invasive species; and - control/eradication of invasive species where found. Prevention of species' migration upstream of the C, O None feasible. n/a n/a western branch confluence (habitat loss). Green Riffle Goby C, O Degradation by flow None feasible. n/a n/a Habitat (Stiphodon elegans) regulation and reduced downstream water quality.

Responsibility Environmental Project Aspect Impact Mitigation action Development/ Component phase Control implementation Take care to avoid introduction of new invasive species to, and spread of existing invasive species within, the Project area through: Introduction/spread of - washing of vehicles, equipment and supplies before entry to the Project Civil works P, C invasive alien species. area; contractor - monitoring for invasive species; and - control/eradication of invasive species where found. C, O Degradation by flow None feasible. n/a n/a regulation and reduced downstream water quality. Schismatogobius tuimanua and Take care to avoid introduction of new invasive species to, and spread of Habitat Stenogobius existing invasive species within, the Project area through: genivittatus Introduction/spread of - washing of vehicles, equipment and supplies before entry to the Project Civil works P, C invasive alien species. area; contractor - monitoring for invasive species; and - control/eradication of invasive species where found. Prevention of species' C, O migration upstream of the None feasible. n/a n/a western branch confluence. Take care to avoid introduction of new invasive species to, and spread of existing invasive species within, the Project area through: Aquatic Natural Habitat Habitat - washing of vehicles, equipment and supplies before entry to the Project Civil works

Introduction/spread of area; contractor P, C invasive alien species. - monitoring for invasive species; and - control/eradication of invasive species where found. Educate local people on the dangers of deliberate introductions of

invasive species.

2.1.1 5.1.1 Implement a strict code of conduct forbidding hunting/trapping, and purchase of wildlife, with heavy penalties. Train all personnel on this code of conduct, and its justification Project construction and operation staff and contractors are a potential risk to priority fauna, particularly birds. Tooth-billed Pigeon has traditionally been a target for hunters (Stirnemann & Taylor-Smith 2019), and any mortality of this species would have severe impacts given its much depleted populations. Other species are also, however, potentially susceptible to harvest in future (e.g., for the reptile trade; Auliya et al. 2016). The Project will thus develop a strict code of conduct forbidding any hunting, trapping, purchase or possession of wildlife, enforced with heavy penalties for individuals and any companies that employ them, and supported by a training program that explains these rules and their justification. This mitigation measure has no significant financial or time cost to operating a good-practice Project. 2.1.2 5.1.2 Install staffed access control on new roads, allowing access to no-one except operational staff, or government officials The Project will establish almost 3 km of new access roads (Section 5.2.1). Without any restrictions, these are likely to stimulate increased access by local people, which may lead to increased levels of forest loss, degradation and hunting in the vicinity of the Project. Management of these induced impacts is the responsibility of the Project, and can be addressed by both enforcement and incentives. Enforcement will consist of physical, staffed barriers to access on any new Project roads, allowing access to no-one except Project staff, contractors, or authorized government officials. This mitigation measure will have small capital costs for establishment of barriers and huts for staffing the barriers (

In order to manage the risk of introducing or spreading invasive species into the forested area within which this Project is proposed, an Invasive Species Management Plan will be developed. This will include at minimum: pressure washing of vehicles, equipment and supplies before entry to Project roads (ideally at one access point before the Project); monitoring for invasive species across the Project area; and control/eradication of invasive species where found in the Project area. Washing need not use substantial amounts of water, and can be replaced by brushing during any periods of low water supply. It is anticipated that costs of a wash station are unlikely to exceed US$5,000 USD. Staffing costs for such wash stations can potentially be cost-effectively combined with those for Project area access barriers (Section 5.1.2). Such preventative measures are generally considerably less costly than measures to control or eradicate invasive species. 2.1.5 5.1.5 Prior to finalization of project designs and any clearance, identify, clearly mark and map all mature native trees, to facilitate avoidance and minimization Understanding of the distribution of native vegetation in the Project area is currently limited (Section A.3). Further, native trees (particularly fruiting trees such as Ficus and Dysoxylum species; Section 5.1.4) in otherwise cleared “plantation” areas are of significant importance to priority birds (Section A.3). As such, it will be important for a botanist to conduct detailed ground surveys prior to finalization of Project designs in order to map native vegetation – particularly mature native trees. These maps will be used to maximize avoidance and minimization of native vegetation clearance in final Project designs. Costs of such botanical surveys are likely to be limited (

Restoration of native species will particularly focus on those of value to priority biodiversity, such as Dysoxylum species that provide fruit for Tooth-billed Pigeon. Stirnemann & Taylor- Smith (2019) provide detailed recommendations (in their Section 6.2) for replanting, which will be incorporated into a Project Restoration Plan. Bonin (2008) estimated costs of restoration and invasive plant control at a degraded site in the Vaisigano watershed to be c.US$700/year. Acknowledging economies of scale, the cost of restoring 1.06 ha over 30 years is here initially estimated to be c.US$30,000. 2.1.8 5.1.8 Regularly maintain and inspect/certificate all vehicles, equipment and machinery to ensure that noise levels conform to international standards Apart from hunting (Section 5.1.1) and vegetation clearance (Section 5.1.6), native fauna are most likely to be disturbed by Project noise. To minimize such disturbance, the Project will adopt an international standard to follow (such as IFC 2007), and regularly inspect and approve all vehicles, equipment and machinery to ensure conformance with this standard. This mitigation measure has no significant financial or time cost to operating a good-practice Project. 2.1.9 5.1.9 Avoid any construction activity during the most sensitive Mao breeding period (June-August inclusive) Of the priority species, disturbance is likely to have the most severe impacts on birds, given their ability to move away from disturbance. This may not be a major impact at some times of year, but can be significant during the breeding season as it can cause birds to abandon nests and produce no young that year. This is of most significance for Mao, which are known to breed in the Project area (Stirnemann & Taylor-Smith 2019). Construction activity, including vegetation clearance, will thus be conducted outside of the most sensitive nesting period for Mao, i.e. June to August (Rebecca Stirnemann in litt. 2019) – ideally avoiding construction activity throughout the breeding season (June to October) where possible (Stirnemann & Taylor-Smith 2019). This mitigation measure has no direct financial costs, but may necessitate some time delays or careful planning to avoid such time delays. 2.1.10 5.1.10 Avoid any construction activity within 150 meters of an occupied Tooth-billed Pigeon or Mao nest The most sensitive areas for disturbance of birds during the breeding season (Section 5.1.9) are active nests. Immediately prior to any vegetation clearance, an experienced expert will thus conduct a survey to ensure Mao breeding is not occurring (Stirnemann & Taylor-Smith 2019). If breeding of this species (or Tooth-billed Pigeon, though less likely) is found, no construction activity – including vegetation clearance – will occur within 150 meters of any areas found or suspected to hold active nests, until the end of the breeding season for that species (Section 5.1.9). This mitigation measure has limited financial costs for surveys (

20 to educate local people on these risks. This mitigation measure has limited financial costs for the Project.

2.2 5.2 Residual impacts Following the impact assessment methodology used in MRDI (2019), residual impacts for Critical Habitat-qualifying (“priority”) biodiversity (Table 1) and Natural Habitat, after the application of Project mitigation (Section 5.1) are assessed in Tables 4 and 5. The ADB SPS requires equivalence in biodiversity compensation. Among other things, this means that the combination of area and quality (“extent × condition”) of each habitat delivered by compensation is equivalent to the combined area and quality of the impacted habitat. The implications of this are explored below for Critical Habitat and Natural Habitat impacts. 2.2.1 5.2.1 Residual impacts on terrestrial Critical Habitat Stirnemann & Taylor-Smith (2019) estimated a residual loss of 24.4 ha of terrestrial Critical Habitat, under the footprint of the Project’s dam wall and reservoir. Additional long-term residual losses are predicted from vegetation clearance for the penstock pipe, small power station and associated roads, plus edge effects related to Project infrastructure. Temporary residual losses are predicted from quarries, an aggregate crushing plant, a batching plant, project site office and stock piles. The residual impacts of loss of terrestrial vegetation are assessed to be of Medium significance. There is also anticipated to be a Low significance residual fragmentation impact for terrestrial species, owing to the Project reservoir and roads. It is challenging to assess habitat quality for Tooth-billed Pigeon (Rebecca Stirnemann pers. comm. 2019) given extremely limited information about its ecology (and thus, for example, what habitat factors determine breeding success), its movements in relation to varying seasonal fruiting of patches of trees of the same species (thus, for example, patches of trees that fruit in June may be of no value if fruit availability in January is limiting), and the varying resilience of different areas to cyclone damage (valleys being much more important refugia in such circumstances). The species appears more tied to fruit availability than overall forest quality; readily visiting isolated fruit trees in otherwise cleared areas. It is likely that invasive alien animals (notably rats and cats) currently play the largest role in limiting populations of Mao, and possibly also Tooth-billed Pigeon, and their density is thus the largest current determinant of habitat quality (Rebecca Stirnemann pers. comm. 2019). Project cleared vegetation for the Project dam and reservoir is estimated to comprise 17.8 ha of secondary forest and 6.6 ha of mixed “plantation” (subsistence home garden) (Stirnemann & Taylor-Smith 2019). The secondary forest is of variable quality, with a mix of native and non- native plant species. When considering impacts it is important to consider not just the area of habitat impacted, but also the quality. It is best practice to combine these as “extent × condition” metrics in a “habitat hectares” or “quality hectares” approach (e.g., Parkes et al. 2003; BBOP 2012). Use of such metrics helps ensure that the combination of area and quality of habitat delivered by compensation is equivalent to the combined area and quality of impacted habitat. Given available data and recognizing the challenges explained above, for the purposes of this assessment secondary forest in the Project vicinity is considered overall approximately 75% of natural quality and “plantation” 60% of natural quality. These quality estimates are based on comparison to a notional “pristine” forest, and are considered here in terms of suitability to priority biodiversity – thus, though substantially non-natural, plantation is rated as 60% quality because it provides many nesting and feeding sites for priority birds. These estimates are based on expert judgement, are preliminary and need further consideration and refinement – ideally using directly-sampled field data. Residual impacts from the Project footprint can thus be envisaged as (17.8 ha (area of secondary forest) × 0.75 (quality of secondary forest) + 6.6 (area of plantation) × 0.6 (quality of plantation) = 17.31 Quality Hectares (QH) of forest.

Based on current Project designs, similar quantitative estimates can be made for all Project infrastructure (Table 4). Most estimates are less precise than those for the Project dam and reservoir, and do not benefit from forest cover maps. At present, other infrastructure is thus precautionarily considered to fall on secondary forest (75% quality) rather than plantation. Several other assumptions are made: (i) access roads will total 2.96 km (including 990 m of temporary roads for construction, which will be inundated by the reservoir) and involve clearance of a c.10 m-wide corridor (Andrew Taylor in litt. 2019); (ii) the penstock pipeline will be c.400 m long (Richard Herweynen in litt. 2019) and involve clearance of a c.5 m-wide corridor; (iii) agriculture in other areas occurs at similar density to that within the dam and reservoir (c.30% of land cover); (iv) edge effects will equate to 50% loss of current forest quality within 10 m of all infrastructure (a precautionary simplification of real effects; Stirnemann & Taylor-Smith 2019); (v) quarry sites and construction access roads fall entirely within the reservoir footprint; (vi) mitigation can largely/entirely remove the risk of agriculture being displaced to new locations, with resulting forest clearance impacts; and (vii) restoration will proceed sufficiently fast that edge effects from temporary construction infrastructure will be negligible.

Table 4. Quantification of Project impacts on terrestrial vegetation Impact Estimated area Estimated Estimated Impact Duration (Hectares) forest quality (Quality Hectares) Dam and reservoir 17.8 75% 13.35 Long-term

6.6 60% 3.96 Long-term

Penstock pipe 0.2 75% 0.15 Long-term

Power station 0.04 75% 0.03 Long-term

Access roads 1.97 75% 1.4775 Long-term

Edge effects 107.2 75% 40.2 Long-term

Construction access roads 0.99 75% 0 Short-term

Quarries 0 75% 0 Short-term

Aggregate crushing plant 0.2 75% 0.15 Short-term

Batching plant 0.06 75% 0.045 Short-term

Project site office 0.1 75% 0.075 Short-term

Stock piles (aggregate and steel pipe) 0.7 75% 0.525 Short-term

Totals

133.81 59.1675 Long-term

1.061 0.795 Short-term

For the sake of this assessment, it is also assumed that all temporary/short-term impacts will be restored, and can reach 25% quality in a reasonable offset timeframe (20-30 years). In this timeframe, in the short-term impact areas, there can thus be assumed to be residual impacts of 0.795 QH (total short-term impact; Table 4) – 1.06 ha (area that can be restored) × 0.25 (quality gain feasible during restoration) = 0.53 Quality Hectares. Overall, the Project can be considered to have long-term terrestrial residual impacts of 59.1675 QH + 0.53 QH = c.59.7

1 0.99 ha of construction roads will be under the inundation zone, so are not double-counted here.

Quality Hectares. Further elaboration of the Project design, refinement of assumptions, and/or habitat mapping across the Project area will be used to refine this preliminary estimate. Residual impacts on terrestrial Natural Habitat are currently considered to be the same as for Critical Habitat, since the information does not currently exist to distinguish these habitat classes on land. 2.2.2 5.2.2 Residual impacts on aquatic Critical Habitat For aquatic Critical Habitat, there are predicted to be three Low-High significance residual impacts. Here, habitat quality impacts have been quantified, in consultation with William Elvey (in litt. 2019). Although habitat quality impacts are based on expert opinion at present, they provide a useful basis for comparison with potential gains (Section 5.3.2). A High significance residual impact is the indirect loss of c.11.4 km of aquatic Critical Habitat in the middle-east branch upstream of the Project reservoir, and c.1.2 km immediately downstream of the Project dam, through prevention/discouragement of fish migration upstream of the western branch confluence (Section 4.2). The species that qualify these stretches of river as Critical Habitat require migratory connectivity, and so will be eliminated by the Project. In the middle-east branch, c.9.7 km is in a natural condition (perhaps 75% quality for the purposes of this assessment). Another 3 km is degraded by abstraction for the existing Alaoa headpond and other downstream flow regulation (so might be considered c.60% quality), of which 1.3 km will be wholly flooded (as discussed above). The 1.2 km immediately downstream of the Project dam is currently c.65% quality at present. Overall, this impact can thus be considered as (9.7×0.75)+((3-1.3)×0.6)+(1.2×0.65) = 9.075 Quality Kilometers of river Critical Habitat. Another Medium significance residual impact is the direct loss of c.1.3 km of river habitat owing to flooding under the Project reservoir (Section 4.2). This is considered broadly natural condition, but impacted by downstream flow regulation (so, for the purposes of this assessment, perhaps 65% quality), and so these impacts can be considered as 1.3×0.65 = 0.845 Quality Kilometers of river Critical Habitat. There is also predicted to be a Low significance residual impact to aquatic Critical Habitat through modification of flows, and potentially reduced water quality, downstream of the Project dam. This impact will affect c.1 km of broadly Natural Habitat (~65% quality) from the Project power station to the Samasoni weir, c.4.2 km of heavily Modified Habitat (considered only 10% quality for the purposes of this assessment) from Samasoni weir to Samasoni Power Station, and c.1 km of Modified Habitat (~50% quality) from the power station to Apia Bay. Further modification of already highly-altered flows is not likely to substantially increase cumulative impacts; speculatively by 10%. This degradation impact may thus be considered to be: (1×0.1)+(4.2×0.1)+(1×0.1) = 0.62 Quality Kilometers of river Critical Habitat. Considering all three impacts discussed above, total Project residual impacts on aquatic Critical Habitat can thus be considered to be 10.54 Quality Kilometers of river Critical Habitat. 2.2.3 5.2.3 Residual impacts on aquatic Natural Habitat Two areas of non-Critical aquatic Natural Habitat exist in the Vaisigano watershed: the stretch upstream from the middle branch weir, and the east branch stretch upstream of the Fale ole Fee weir (Figure 1). The latter is expected to experience residual Project impacts through elimination of migratory species upstream of the dam barrier (Section 4.2). This will degrade c.8.2 km of Natural Habitat in the east branch. This is currently in a degraded condition (~50% quality) and – for the purposes of this assessment – could be considered to be degraded to c.40% quality Modified Habitat. Overall, this degradation impact may thus be considered to be: (8.2×(0.5-0.4)) = 0.82 Quality Kilometers of river Natural Habitat. While this estimate is imprecise and subjective, it would be challenging to improve it significantly without objective monitoring of quality metrics across the Vaisigano watershed.

Table 5. Residual impacts after mitigation for Critical Habitat-qualifying biodiversity Residual impact after implementation of Significance mitigation measures Environmental Project of impact Preparation, Key Residual Aspect Impact Operation Phase Component phase without Construction, Impacts mitigation and Worksite Day 1 Year 10 Closure Phases Long-term loss of c.27 ha of vegetation; P, C Vegetation clearance. M fragmentation by Medium Medium Medium roads and reservoir. Long-term loss of c. Edge effects and habitat fragmentation 107 ha of vegetation; P, C M Apia Catchments Key Vegetation resulting from vegetation clearance. fragmentation by Biodiversity Area cover Medium Medium Medium roads and reservoir. Displacement of agriculture, resulting in P, C L vegetation clearance elsewhere. Negligible Negligible Negligible n/a Forest loss/degradation, owing to induced O L access for people via project roads. Negligible Negligible Negligible n/a Introduction/spread of invasive alien P, C H species. Negligible Negligible Negligible n/a Long-term loss of c.27 P, C Vegetation clearance. M Medium Medium Medium ha of vegetation. Long-term loss of c. Edge effects and habitat fragmentation 107 ha of vegetation; P, C M resulting from vegetation clearance. fragmentation by Medium Medium Medium roads and reservoir. Habitat Displacement of agriculture, resulting in P, C L vegetation clearance elsewhere. Negligible Negligible Negligible n/a Forest loss/degradation, owing to induced Tooth-billed Pigeon O M access for people via project roads. Negligible Negligible Negligible n/a (Didunculus strigirostris) Introduction/spread of invasive alien and Mao (Gymnomyza P, C H species. Negligible Negligible Negligible n/a samoensis) Displacement of species due to noise, Distribution P, C presence of machinery and equipment and L presence of staff. Low Negligible Negligible n/a Introduction/spread of invasive alien P, C, O H species (causing predation/smothering). Negligible Negligible Negligible n/a Mortality of individuals, from poaching by Mortality C L construction workers. Negligible Negligible Negligible n/a Mortality of individuals, owing to induced O M access for hunters via project roads. Negligible Negligible Negligible n/a Olive Small-scaled Skink Habitat P, C Vegetation clearance. M Long-term loss of c.27 (Emoia lawesi), Samoa Medium Medium Medium ha of vegetation;

Residual impact after implementation of Significance mitigation measures Environmental Project of impact Preparation, Key Residual Aspect Impact Operation Phase Component phase without Construction, Impacts mitigation and Worksite Day 1 Year 10 Closure Phases Skink (Emoia samoensis), fragmentation by Thaumatodon roads and reservoir. hystricelloides, Long-term loss of c. Drymophloeus samoensis Edge effects and habitat fragmentation 107 ha of vegetation; P, C M and Clinostigma resulting from vegetation clearance. fragmentation by samoense Medium Medium Medium roads and reservoir. Displacement of agriculture, resulting in P, C L vegetation clearance elsewhere. Negligible Negligible Negligible n/a Forest loss/degradation, owing to induced O L access for people via project roads. Negligible Negligible Negligible n/a Introduction/spread of invasive alien P, C H species. Negligible Negligible Negligible n/a Introduction/spread of invasive alien Mortality P, C, O H species (causing predation/smothering). Negligible Negligible Negligible n/a C, O Loss of habitat in the reservoir. M Long-term loss of c.1.3 Medium Medium Medium km of aquatic habitat. Prevention of species' migration upstream Long-term loss of C, O of the western branch confluence (habitat H c.12.6 km of habitat Fat-snout Goby loss). High High High upstream. (Sicyopterus pugnans) Degradation of c.6.5 Habitat and Stiphodon km of habitat Degradation by flow regulation and downstream by hydroreibatus C, O L L L L reduced downstream water quality. modified flows, and potentially reduced water quality. Introduction/spread of invasive alien P, C M species. Negligible Negligible Negligible n/a Prevention of species' migration upstream C, O of the western branch confluence (habitat H Long-term loss of c.1.2 loss). High High High km of aquatic habitat. Degradation of c.6.5 km of habitat Green Riffle Goby Habitat Degradation by flow regulation and downstream by (Stiphodon elegans) C, O L L L L reduced downstream water quality. modified flows, and potentially reduced water quality. Introduction/spread of invasive alien P, C M species. Negligible Negligible Negligible n/a

2.3 5.3 No net loss/net gain approach The ADB Safeguard Policy Statement requires ‘measures to avoid, minimize, or mitigate potentially adverse impacts and risks’, as outlined in Section 5.1. Nonetheless, some residual impacts cannot be fully mitigated, and – on a precautionary basis – it is recognized that this Project may have significant, though small, residual impacts of forest loss and fragmentation (Section 5.2). In such cases, ADB requires ‘compensatory measures, such as biodiversity offsets, to achieve no net loss or a net gain of the affected biodiversity’. These compensatory measures should ensure that, overall, the high biodiversity value of the Critical Habitat is maintained, along with populations of Endangered and Critically Endangered species. Drawing on international good practice, the choice of an appropriate compensation measure to reach no net loss or net gain should – in particular – be comparable, additional and lasting (e.g., Gardner et al. 2013). “Comparable” means that the compensation measure should produce similar biodiversity gains to residual impacts (in scale, type of biodiversity, etc.), equating – for this Project – to gains in habitat for six terrestrial and five fish species, ideally in or near the Apia Catchments Key Biodiversity Area. “Additional” means that gains produced by the compensation measure would not have happened anyway, in the absence of the Project. “Lasting” means that gains should last as long as residual impacts, in the case of this Project into the long-term. The compensation measure should ideally also be practical, i.e. cost-effective and relatively easy to implement – such as through a contract to one entity, rather than through complex multi-institutional partnerships. This Project’s predicted residual impacts are: direct loss, and fragmentation, of terrestrial Critical Habitat (Section 4.1); direct and indirect loss and degradation of aquatic Critical Habitat (Section 4.2); and degradation of aquatic Natural Habitat (Section 4.3). The ADB Safeguard Policy Statement (SPS) requires compensation (“offset”) measures to address these residual impacts. Compensation for ADB-funded projects is required to focus on similar biodiversity. As such, this Project will need to improve the status of the impacted forest type and the priority species it holds, and improve the status of similar river habitats in the catchment. Approaches to these are explained in Sections 5.3.1-5.3.3. These approaches and others will be detailed further in a Biodiversity Offset Plan (covering terrestrial, aquatic, policy and institutional support). The total cost of the approaches outlined in Sections 5.3.1-5.3.3 is initially estimated at US$155,000-320,000/year for forest restoration and invasive species control, plus US$250,000 for translocation of Mao, pending more detailed planning and budgeting. Abundant experience elsewhere demonstrates that is not appropriate to budget for such costs on an annual basis (e.g., from annual Project revenues). As such, the optimal approach is an up-front trust fund-type mechanism, which can generate annual requirements. This endowment would need to be c.US$4.2-8.3 million. Overall, the Project is compliant for biodiversity with the ADB Safeguard Policy Statement (2009) because, after mitigation, (i) there are no measurable adverse impacts, or likelihood of such, on the critical habitat which could impair its high biodiversity value or the ability to function, and (ii) the project is not anticipated to lead to a reduction in the population of any recognized endangered or critically endangered species or a loss in area of the habitat concerned such that the persistence of a viable and representative host ecosystem be compromised. 2.3.1 5.3.1 Approach to residual impacts on forested Critical Habitat The Project is estimated to have residual impacts of 59.7 QH on forested Critical Habitat (Section 5.2.1). These are best compensated by restoration of forest in other areas of the Vaisigano River watershed, with the expectation that a similar suite of species will be conserved through such restoration (restoration should not, therefore, be carried out at considerably higher altitudes). This restoration will also have the side benefit of supporting the flood control efforts of the Project. This may involve reforestation of cleared areas, or

21 enrichment planting, and will also need to include invasive species control. If restoration efforts proceed without invasive species control, it is believed that priority species (at least of the birds, which are better-known than most others) will continue to decline (Rebecca Stirnemann pers. comm. 2019). Conversely, if invasive species control proceeds without restoration, there will be a limited amount of habitat into which successfully breeding species can expand. Priorities for such restoration will be decided after a survey and mapping exercise that identifies restoration areas that would most benefit priority biodiversity, based on criteria such as establishing corridors between forest fragments or enhancing areas currently known to be of value. Priorities for invasive species control are rats and cats (which directly predate priority species), Yellow Crazy Ants (which appear to eradicate Samoa Skink), key invasive plants such as rubber trees (which crowd out native vegetation), and pigs (which otherwise hamper restoration efforts by destroying new plantings). Overall, restoration and invasive species control efforts would be best undertaken in two or three areas – rather than one – to best hedge against failure of any one site, and to offer more potential benefits from varying seasonality of fruit trees at multiple sites. The area of forest requiring restoration will depend on the quality of priority areas chosen for restoration and the appropriate approach (reforestation, enrichment planting, and/or invasive species control) within them. For example, if the approach chosen is to focus on restoration and invasive species control in highly degraded secondary forest (currently c.25% quality), in order to bring it up to the quality of less degraded secondary forest (c.75% quality), each hectare could contribute a gain of 1 (area) × (0.75 (restoration quality goal) – 0.25 (current quality of highly degraded secondary forest)) = 0.5 Quality Hectares (QH). To compensate for the 59.7 QH of residual impacts, there would thus need to be an offset size of 59.7 QH (residual impact) / 0.5 (quality gain per hectare of offset) = c.120 ha. At the other end of the spectrum, an approach focusing on enrichment planting and invasive species control might possibly improve the quality of less degraded secondary forest (c.75% quality) to near natural quality for priority species (~100% quality). In such a case, each hectare could contribute a gain of 1 (area) × (1 (restoration quality goal) – 0.75 (current quality of less degraded secondary forest)) = 0.25 Quality Hectares (QH). To compensate for the 59.7 QH of residual impacts, there would thus need to be an offset size of 59.7 QH (residual impact) / 0.25 (quality gain per hectare of offset) = c.240 ha. An important consideration is that, to ensure these actions represent a valid “lasting” offset, their gains must endure for as long as Project impacts (i.e., until any such time as Project dam and reservoir are decommissioned and their footprint restored to at least pre-Project quality). The Project will thus plan and budget for these actions to effectively be carried out in perpetuity. Otherwise, biodiversity gains from – for example – only 20 years of restoration and invasive species control would likely all be lost 10 years later. Costs of forest restoration and invasive species control are very context-specific. Fortunately, a relevant publicly-available estimate of such costs is available in Bonin (2008). This includes a proposed budget for restoration of native plants and control of invasive plants across c.78 ha at Mount Vaea, on the outskirts of Apia in the lower reaches of the Vaisigano watershed. A five-year program of research, field trials and implementation is estimated to cost at least US$270,000. Considering two restoration offsets for this Project totaling 120-240 ha, restoration of native plants and control of invasive plants might thus cost in the region of US$80,000-170,000/year, although it is anticipated that such costs would reduce over time. Few nationally-relevant costs have been published for control of invasive species other than plants. Tye & Butler (2013) state a total cost of c.US$400,000 in an attempt to control of rats across Nu’utele and Nu’ula (totaling 133 ha) in 2009. That project aimed to eradicate rats on islands (with increased logistical costs), needed to capture non-target species at risk of eating rat baits, and included a number of additional biodiversity monitoring programs, so is likely to be considerably more expensive than control of invasive fauna in a similar area of the Vaisigano watershed. The majority of published costs elsewhere relate to invasive species eradication on islands, rather than control in mainland areas. For mainland control of invasive

22 fauna, costs depend on methods. Trapping is likely to be the most effective method for most invasive fauna in areas >50 ha (Norbury et al. 2014), costing around US$75/ha/year (converted from NZ$) for areas of around 100 ha. Nonetheless, other options will be explored during detailed planning – e.g., mainland control of invasive predators using aerially distributed toxins can cost

23 station. This 4.2 km stretch is currently highly Modified Habitat (for the purposes of this assessment, perhaps 10% of natural quality), but could be substantially improved by reinstatement of year-round flows (perhaps to 80% of natural quality). As such, this restoration can be considered to contribute (4.2×(0.8-0.1)) = 2.94 Quality Kilometers of river Critical Habitat. Entura (2019b) estimated that restoration of ecological flows from the middle branch weir would not only contribute to improvement of the final 1.5 km of the middle branch (from perhaps 10 to 75% quality), but would also improve the quality of up to 7.9 km of the middle branch upstream of this weir (from perhaps 50 to 90% quality) by allowing access to most migratory species. This can be considered re-establishment of good quality Critical Habitat, and thus would contribute (1.5×(0.75-0.1))+ (7.9×(0.9-0.5)) = 11.41 Quality Kilometers of river Critical Habitat. Restoration of ecological flows downstream will improve the accessibility of the western branch to migratory species (Entura 2019b), thus improving its overall quality to near natural condition. Considering this 12.3 km stretch at present to be broadly Natural but slightly modified (for the purposes of this assessment, perhaps 75% of natural quality), this improvement can be considered to contribute 12.3×(0.95-0.75) = 2.46 Quality Kilometers of river Critical Habitat. Considering all three environmental flow offset benefits discussed above, total benefits to aquatic Critical Habitat can thus be considered to be 16.81 Quality Kilometers of river Critical Habitat, far in excess of the predicted 9.9225 Quality Kilometers of residual Project impacts. All of these quality gains cannot, however, be considered “additional” as national policy states that minimum flows will be released from existing projects, including the current middle branch weir and Samasoni weir, following MWH (2009). The current requirement following MWH (2009) is 0.2 m3/s from the Samasoni weir and 0.07 m3/s from the middle branch weir. Proposals by Entura (2019b) increase flows from the Samasoni weir (to 0.3 m3/s), and are similar from the middle branch weir (0.06 m3/s; updated per William Elvey in litt. 2019), but also add in requirements for pulse events of higher flows which are critical to maintaining geomorphic processes and simulating natural cues in the ecology of aquatic species (e.g., migration, breeding). It is thus challenging to assess what proportion of the proposals by Entura (2019a) are truly additional. If just 65% additionality is assumed, the 16.81 Quality Kilometers of offset gains is sufficient to compensate for the 10.54 Quality Kilometers of residual Project impacts. Further, the Project aims to also provide indirect compensation benefits for aquatic Natural and Critical Habitat by providing policy and institutional support. There is no direct cost of increasing flows from the Samasoni weir from the current requirement to 0.3 m3/s, but there are indirect costs XXXXXXXXXXXXXXXXXXX. Policy and institutional support is estimated to cost c.$USXXXX. 2.3.3 5.3.3 Approach to residual impacts on river Natural Habitat Residual impacts on non-Critical aquatic Natural Habitat are estimated to be 0.82 Quality Kilometers of river (Section 5.2.3). It is anticipated that the middle branch (currently non- Critical Natural Habitat) can be restored to Critical Habitat through restoration of ecological flows (Section 5.3.2). Apart from this, there is no realistic prospect for improvements to river Natural Habitat in the Vaisigano watershed, since the remaining non-Critical Natural Habitat stretch is the east branch stretch isolated above the Fale ole Fee weir. The residual impact on Natural Habitat is small, and the Project aims to compensate indirectly for these impacts by providing policy and institutional support (Section 5.3.2).

3. 6 Biodiversity monitoring The Project will undertake a general program of monitoring during site preparation, construction and worksite closure (citation to the EIA). Within that program, specific monitoring will be undertaken for Critical Habitat-qualifying biodiversity (Table 1) to: • Confirm presence of effective mitigation (Table 3); • Confirm predicted negligible impacts after mitigation by the operations phase for most priority biodiversity (Table 4); and • Verify or adjust quantified estimates of residual Project impacts presented in this document (Sections 5.2.1 and 5.2.2) – from vegetation clearance, edge effects, flooding of river habitat by the reservoir, and prevention of species’ migration upstream – in order to refine understanding of the scale of compensation measures (Section 5.3). The Project will also put in place a long-term monitoring program, to: • Verify or adjust quantified estimates of the success of restoration in temporarily- disturbed sites (Section 5.2.1); • Verify or adjust quantified estimates of the success of restoration and invasive species control in the Vaisigano watershed, as part of the Project’s no net loss/net gain approach (Section 5.3.1); • Verify or adjust quantified estimates of the success of reinstatement of environmental flows in the Vaisigano watershed, as part of the Project’s no net loss/net gain approach (Section 5.3.2); and • Based on the above results, guide adaptive management to ensure the Project achieves at least no net loss for Natural Habitat and net gain for Critical Habitat. This long-term monitoring will need to last for the life of the Project (essentially in perpetuity), in order to ensure that the Project not only achieves net gain for Critical Habitat, but also that this gain is sustained over time (to ensure the offset is “lasting”; Section 5.3). As such, long- term monitoring will be integrated into Project operational plans. A broad approach to both short-term and long-term monitoring for Critical Habitat-qualifying biodiversity is outlined in Table 6. This approach will be developed further into a set of detailed Biodiversity Management and Monitoring Plans for groups of terrestrial biodiversity (e.g., aquatic species, birds and bats, etc.). Table 6 outlines key areas of monitoring necessary to assess changes in the state of potentially Critical Habitat-qualifying ecosystems and species, changes in threats to this biodiversity, and progress of project mitigation/offset actions. Together, these approaches to monitoring ‘state’, ‘pressure’ and ‘response’ for Critical Habitat- qualifying biodiversity will enable the project to assess progress towards No Net Loss. For all aspects of monitoring, it will be necessary to establish higher and/or lower thresholds which outline the expected natural variation within indicators. Should monitoring show indicators above/below these safe boundaries, adaptive management of project mitigation or operation will need to be considered.

Table 6. Key areas of monitoring necessary to assess changes in the state of priority biodiversity, changes in threats, and progress of project mitigation actions

Where is the How is the When is the Environmental Project What parameter is parameter to parameter to parameter to be Institutional Aspect Impact Mitigation action Component phase to be monitored? be be monitored responsibility monitored? monitored? (frequency)? Prior to finalization of project designs Map of all mature and any clearance, native trees in Review of Once, prior to identify, clearly mark Project area Project Area expert- construction/clea and map all mature produced prior to any of Influence produced map rance native trees, to construction or facilitate avoidance vegetation clearance and minimisation. Minimize clearance Unannounced Vegetation clearance of native vegetation Review of inspections at by Project staff and at the Project site Project least quarterly, contractors is as and around Project Area incident during minimal as legally associated roads logbook; visual preparation and and technically and other inspection construction necessary infrastructure; using phases already cleared or modified areas for construction Apia Catchments wherever possible. Vegetation Vegetation Unannounced Key Biodiversity P, C Prioritize avoidance Review of cover clearance. inspections at Area of Ficus and Project Actual area and least quarterly, Dysoxylum trees vegetation quality of vegetation Project Area during (which may provide clearance cleared preparation and seasonal food records; visual construction sources for Tooth- inspection phases billed Pigeon), and attempt to relocate any of these which cannot be avoided. Review of Restoration Plan Once, prior to Project Area Restoration developed restoration Plan Replant native Annual vegetation (including inspections for Dysoxylum species) Visual first five years of in any temporarily Area and quality of inspection by Project Area restoration, then disturbed areas. restored forest qualified every five years expert until restoration targets met

Where is the How is the When is the Environmental Project What parameter is parameter to parameter to parameter to be Institutional Aspect Impact Mitigation action Component phase to be monitored? be be monitored responsibility monitored? monitored? (frequency)? Unannounced Minimize clearance Vegetation clearance Review of inspections at of native vegetation by Project staff and Project least quarterly, at the Project site contractors is as Project Area Edge effects and incident during and around minimal as legally of Influence habitat logbook; visual preparation and associated roads and technically fragmentation inspection construction P, C and other necessary resulting from phases infrastructure; using vegetation Annually during already cleared or clearance. Actual area and Surveys by Project modified areas for quality impact of Project Area specialist sub- construction and construction edge effects contractor for the five wherever possible. following years Resettlement Plan developed prior to construction/clearanc Review of Once, prior to e, including Project Area Resettlement construction/clea consideration of how of Influence Plan rance Engage and educate to compensate local the local community, people who lose including providing access to land incentives to All Project-affected Review of Displacement of conserve priority people engaged and community Unannounced agriculture, resulting biodiversity - such have access to engagement inspections P, C in vegetation as employment in equivalent or greater Project Area records; quarterly during clearance restoration, invasive benefits from Project of Influence review of preparation and elsewhere. species control and activities such as Project construction monitoring - appropriate incident phases prioritising Project- employment logbook affected people. No opening of new Remote Annually during agricultural areas in sensing, Project the Vaisigano Project Area verified by construction and watershed by of Influence ground for the five Project-affected surveys following years people Install staffed Review of Unannounced access control on Forest Controls on use of Project inspections at new roads, allowing loss/degradation, Project roads ensure incident least quarterly, access to no-one O owing to induced no access for Project Area logbook; during except operational access for people loggers/poachers/hu external preparation and staff, or government via project roads. nters reports; visual construction officials, and inspection phases inspecting departing

Resettlement Plan developed prior to construction/clearanc Review of Once, prior to e, including Project Area Resettlement construction/clea consideration of how of Influence Engage and educate Plan rance to compensate local the local community, people who lose including providing access to land incentives to All Project-affected Review of conserve priority people engaged and community Unannounced biodiversity - such have access to engagement inspections as employment in equivalent or greater Project Area records; quarterly during restoration, invasive benefits from Project of Influence review of preparation and species control and activities such as Project construction monitoring - appropriate incident phases prioritising Project- employment logbook affected people. Remote Annually during No logging or sensing, Project opening of new Project Area verified by construction and agricultural areas of Influence ground for the five from Project roads surveys following years Take care to avoid Unannounced introduction of new inspections at Washing of vehicles, Transit site invasive species to, least quarterly equipment and outside and spread of Inspections during supplies before entry Project Area existing invasive preparation and to Project area of Influence species within, the construction Project area phases through: Annually, in Abundance/spread of Introduction/spread - washing of Surveys by summer during invasive alien Project Area P, C of invasive alien vehicles, equipment specialist sub- preparation and species in Project of Influence species. and supplies before contractor construction area entry to the Project phases area; Quarterly, during - monitoring for Control of Records of preparation and invasive species; new/spreading areas invasive construction Project Area and of invasive alien species phases, and of Influence - control/eradication species in Project control; annually of invasive species area inspections afterwards until where found. any Project-

Where is the How is the When is the Environmental Project What parameter is parameter to parameter to parameter to be Institutional Aspect Impact Mitigation action Component phase to be monitored? be be monitored responsibility monitored? monitored? (frequency)? induced spread of invasive species is eliminated Prior to finalization of project designs Map of all mature and any clearance, native trees in Review of Once, prior to identify, clearly mark Project area Project Area expert- construction/clea and map all mature produced prior to any of Influence produced map rance native trees, to construction or facilitate avoidance vegetation clearance and minimisation. Minimize clearance Unannounced Vegetation clearance of native vegetation Review of inspections at by Project staff and at the Project site Project least quarterly, contractors is as and around Project Area incident during minimal as legally associated roads logbook; visual preparation and and technically and other inspection construction necessary infrastructure; using phases already cleared or Tooth-billed modified areas for Pigeon construction (Didunculus Vegetation Habitat P, C wherever possible. strigirostris) and clearance. Unannounced Prioritize avoidance Review of Mao (Gymnomyza inspections at of Ficus and Project samoensis) Actual area and least quarterly, Dysoxylum trees vegetation quality of vegetation Project Area during (which may provide clearance cleared preparation and seasonal food records; visual construction sources for Tooth- inspection phases billed Pigeon), and attempt to relocate any of these which cannot be avoided. Unannounced Avoid any No construction inspections each vegetation clearance activity, including September and Surveys by within 150 meters of vegetation clearance, October, in all Project Area specialist sub- an occupied Tooth- taking place within years of the contractor billed Pigeon or Mao 150 m of a priority preparation and nest. bird nest construction phases

Where is the How is the When is the Environmental Project What parameter is parameter to parameter to parameter to be Institutional Aspect Impact Mitigation action Component phase to be monitored? be be monitored responsibility monitored? monitored? (frequency)? Review of Restoration Plan Once, prior to Project Area Restoration developed restoration Plan Replant native Annual vegetation (including inspections for Dysoxylum species) Visual first five years, in any temporarily Area and quality of inspection by Project Area then every five disturbed areas. restored forest qualified years until expert restoration targets met Unannounced Minimize clearance Vegetation clearance Review of inspections at of native vegetation by Project staff and Project least quarterly, at the Project site contractors is as Project Area Edge effects and incident during and around minimal as legally of Influence habitat logbook; visual preparation and associated roads and technically fragmentation inspection construction P, C and other necessary resulting from phases infrastructure; using vegetation Annually during already cleared or clearance. Actual area and Surveys by Project modified areas for quality impact of Project Area specialist sub- construction and construction edge effects contractor for the five wherever possible. following years Resettlement Plan developed prior to construction/clearanc Review of Once, prior to e, including Project Area Resettlement construction/clea consideration of how of Influence Engage and educate Plan rance to compensate local the local community, people who lose including providing access to land incentives to Displacement of All Project-affected Review of conserve priority agriculture, resulting people engaged and community Unannounced biodiversity - such P, C in vegetation have access to engagement inspections as employment in clearance equivalent or greater Project Area records; quarterly during restoration, invasive elsewhere. benefits from Project of Influence review of preparation and species control and activities such as Project construction monitoring - appropriate incident phases prioritising Project- employment logbook affected people. Remote Annually during No opening of new sensing, Project agricultural areas in Project Area verified by construction and the Vaisigano of Influence ground for the five watershed by surveys following years

Install staffed access control on Review of Unannounced new roads, allowing Controls on use of Project inspections at access to no-one Project roads ensure incident least quarterly, except operational no access for Project Area logbook; during staff, or government loggers/poachers/hu external preparation and officials, and nters reports; visual construction inspecting departing inspection phases vehicles for poached wildlife. Resettlement Plan developed prior to construction/clearanc Review of Once, prior to Forest e, including Project Area Resettlement construction/clea loss/degradation, consideration of how of Influence Engage and educate Plan rance O owing to induced to compensate local the local community, access for people people who lose including providing via project roads. access to land incentives to All Project-affected Review of conserve priority people engaged and community Unannounced biodiversity - such have access to engagement inspections as employment in equivalent or greater Project Area records; quarterly during restoration, invasive benefits from Project of Influence review of preparation and species control and activities such as Project construction monitoring - appropriate incident phases prioritising Project- employment logbook affected people. Remote Annually during No logging or sensing, Project opening of new Project Area verified by construction and agricultural areas of Influence ground for the five from Project roads surveys following years Take care to avoid Unannounced introduction of new inspections at Washing of vehicles, Transit site Introduction/spread invasive species to, least quarterly equipment and outside P, C of invasive alien and spread of Inspections during supplies before entry Project Area species. existing invasive preparation and to Project area of Influence species within, the construction Project area phases

Where is the How is the When is the Environmental Project What parameter is parameter to parameter to parameter to be Institutional Aspect Impact Mitigation action Component phase to be monitored? be be monitored responsibility monitored? monitored? (frequency)? through: Annually, in Abundance/spread of - washing of Surveys by summer during invasive alien Project Area vehicles, equipment specialist sub- preparation and species in Project of Influence and supplies before contractor construction area entry to the Project phases area; Quarterly, during - monitoring for preparation and invasive species; construction and Control of Records of phases, and - control/eradication new/spreading areas invasive annually Project Area of invasive species of invasive alien species afterwards until of Influence where found. species in Project control; any Project- area inspections induced spread of invasive species is eliminated Noise levels of Unannounced Regularly maintain Project vehicles, inspections Review of and equipment and quarterly during Project Area certificates; inspect/certificate all machinery against preparation and inspections vehicles, equipment international construction and machinery to standards phases ensure that noise Annually during levels conform to Surveys by Project Density of Mao in international Project area specialist sub- construction and Project area standards. contractor for the five following years Displacement of Unannounced species due to Avoid any inspections noise, presence of construction activity No construction Distribution P, C twice from June- machinery and during the most activity, including August, in all equipment and sensitive Mao vegetation clearance, Project Area Inspections years of the presence of staff. breeding period taking place in June- preparation and (June-August August, inclusive construction inclusive). phases Unannounced Avoid any No construction inspections each construction activity activity, including September and Surveys by within 150 meters of vegetation clearance, October, in all Project Area specialist sub- an occupied Tooth- taking place within years of the contractor billed Pigeon or Mao 150 m of a priority preparation and nest. bird nest construction phases

Where is the How is the When is the Environmental Project What parameter is parameter to parameter to parameter to be Institutional Aspect Impact Mitigation action Component phase to be monitored? be be monitored responsibility monitored? monitored? (frequency)? Unannounced inspections at Washing of vehicles, Transit site Take care to avoid least quarterly equipment and outside introduction of new Inspections during supplies before entry Project Area invasive species to, preparation and to Project area of Influence and spread of construction existing invasive phases species within, the Annually, in Abundance/spread of Project area Surveys by summer during invasive alien Project Area Introduction/spread through: specialist sub- preparation and species in Project of Influence of invasive alien - washing of contractor construction area P, C, O species (causing vehicles, equipment phases predation/ and supplies before Quarterly, during smothering). entry to the Project preparation and area; construction - monitoring for Control of Records of phases, and invasive species; new/spreading areas invasive annually Project Area and of invasive alien species afterwards until of Influence - control/eradication species in Project control; any Project- of invasive species area inspections induced spread where found. of invasive Mortality species is eliminated Implement a strict code of conduct Review of forbidding training Unannounced Mortality of hunting/trapping, records; inspections individuals, from and purchase of Staff adherence to review of quarterly during C poaching by Project Area wildlife, with heavy best practice Project preparation and construction penalties. Train all incident construction workers. personnel on this logbook; phases code of conduct, inspections and its justification. Install staffed access control on Review of Unannounced new roads, allowing Mortality of Controls on use of Project inspections at access to no-one individuals, owing to Project roads ensure incident least quarterly, except operational O induced access for no access for Project Area logbook; during staff, or government hunters via project loggers/poachers/hu external preparation and officials, and roads. nters reports; visual construction inspecting departing inspection phases vehicles for poached wildlife.

restoration, invasive benefits from Project of Influence review of preparation and species control and activities such as Project construction monitoring - appropriate incident phases prioritising Project- employment logbook affected people. Unannounced No incidences of Review of inspections hunting of Tooth- Project Area Project quarterly during

billed Pigeon or other of Influence incident preparation and priority fauna logbook construction phases Prior to finalization of project designs Map of all mature and any clearance, native trees in Review of Once, prior to identify, clearly mark Project area Project Area expert- construction/clea and map all mature produced prior to any of Influence produced map rance Olive Small-scaled native trees, to construction or Skink (Emoia facilitate avoidance vegetation clearance lawesi), Samoa and minimisation. Skink (Emoia Unannounced Vegetation clearance samoensis), Minimize clearance Review of inspections at Vegetation by Project staff and Thaumatodon Habitat P, C of native vegetation Project least quarterly, clearance. contractors is as hystricelloides, at the Project site Project Area incident during minimal as legally Drymophloeus and around logbook; visual preparation and and technically samoensis and associated roads inspection construction necessary Clinostigma and other phases samoense infrastructure; using Review of Unannounced already cleared or Project Actual area and inspections at modified areas for vegetation quality of vegetation Project Area least quarterly, construction clearance cleared during wherever possible. records; visual preparation and inspection

Where is the How is the When is the Environmental Project What parameter is parameter to parameter to parameter to be Institutional Aspect Impact Mitigation action Component phase to be monitored? be be monitored responsibility monitored? monitored? (frequency)? construction phases Review of Restoration Plan Once, prior to Project Area Restoration developed restoration Plan Replant native Annual vegetation (including inspections for Dysoxylum species) Visual first five years, in any temporarily Area and quality of inspection by Project Area then every five disturbed areas. restored forest qualified years until expert restoration targets met Vegetation clearance by Project staff and contractors is as minimal as legally Unannounced Minimize clearance and technically Review of inspections at of native vegetation necessary; Canopy Project least quarterly, at the Project site connectivity along Project Area Edge effects and incident during and around new roads is of Influence habitat logbook; visual preparation and associated roads identified, options for fragmentation inspection construction P, C and other preservation resulting from phases infrastructure; using identified, and vegetation already cleared or connectivity clearance. modified areas for preserved wherever construction possible wherever possible. Annually during Actual area and Surveys by Project quality impact of Project Area specialist sub- construction and edge effects contractor for the five following years Engage and educate Resettlement Plan the local community, developed prior to construction/clearanc including providing Review of Once, prior to incentives to e, including Project Area Displacement of Resettlement construction/clea conserve priority consideration of how of Influence agriculture, resulting Plan rance biodiversity - such to compensate local P, C in vegetation as employment in people who lose clearance restoration, invasive access to land elsewhere. species control and All Project-affected Review of Unannounced monitoring - people engaged and Project Area community inspections

prioritising Project- have access to of Influence engagement quarterly during affected people. equivalent or greater records; preparation and

Where is the How is the When is the Environmental Project What parameter is parameter to parameter to parameter to be Institutional Aspect Impact Mitigation action Component phase to be monitored? be be monitored responsibility monitored? monitored? (frequency)? benefits from Project review of construction activities such as Project phases appropriate incident employment logbook No opening of new Remote Annually during agricultural areas in sensing, Project the Vaisigano Project Area verified by construction and watershed by of Influence ground for the five Project-affected surveys following years people Install staffed Review of Unannounced access control on Controls on use of Project inspections at new roads, allowing Project roads ensure incident least quarterly, access to no-one no access for Project Area logbook; during except operational loggers/poachers/hu external preparation and staff, or government nters reports; visual construction officials. inspection phases Resettlement Plan developed prior to construction/clearanc Review of Once, prior to e, including Project Area Resettlement construction/clea consideration of how of Influence Forest Engage and educate Plan rance to compensate local loss/degradation, the local community, people who lose O owing to induced including providing access to land access for people incentives to All Project-affected Review of via project roads. conserve priority people engaged and community Unannounced biodiversity - such have access to engagement inspections as employment in equivalent or greater Project Area records; quarterly during restoration, invasive benefits from Project of Influence review of preparation and species control and activities such as Project construction monitoring - appropriate incident phases prioritising Project- employment logbook affected people. Remote Annually during No logging or sensing, Project opening of new Project Area verified by construction and agricultural areas of Influence ground for the five from Project roads surveys following years Take care to avoid Unannounced Washing of vehicles, Transit site Introduction/spread introduction of new inspections at equipment and outside P, C of invasive alien invasive species to, Inspections least quarterly supplies before entry Project Area species. and spread of during to Project area of Influence existing invasive preparation and

Where is the How is the When is the Environmental Project What parameter is parameter to parameter to parameter to be Institutional Aspect Impact Mitigation action Component phase to be monitored? be be monitored responsibility monitored? monitored? (frequency)? species within, the construction Project area phases through: Annually, in Abundance/spread of - washing of Surveys by summer during invasive alien Project Area vehicles, equipment specialist sub- preparation and species in Project of Influence and supplies before contractor construction area entry to the Project phases area; Quarterly, during - monitoring for preparation and invasive species; construction and Control of Records of phases, and - control/eradication new/spreading areas invasive annually Project Area of invasive species of invasive alien species afterwards until of Influence where found. species in Project control; any Project- area inspections induced spread of invasive species is eliminated Unannounced inspections at Washing of vehicles, Transit site Take care to avoid least quarterly equipment and outside introduction of new Inspections during supplies before entry Project Area invasive species to, preparation and to Project area of Influence and spread of construction existing invasive phases species within, the Annually, in Abundance/spread of Project area Surveys by summer during invasive alien Project Area Introduction/spread through: specialist sub- preparation and species in Project of Influence of invasive alien - washing of contractor construction area Mortality P, C, O species (causing vehicles, equipment phases predation/smotherin and supplies before Quarterly, during g). entry to the Project preparation and area; construction - monitoring for Control of Records of phases, and invasive species; new/spreading areas invasive annually Project Area and of invasive alien species afterwards until of Influence - control/eradication species in Project control; any Project- of invasive species area inspections induced spread where found. of invasive species is eliminated Fat-snout Goby Loss of habitat in the Habitat C, O None realistic. n/a n/a n/a n/a (Sicyopterus reservoir.

Where is the How is the When is the Environmental Project What parameter is parameter to parameter to parameter to be Institutional Aspect Impact Mitigation action Component phase to be monitored? be be monitored responsibility monitored? monitored? (frequency)? Degradation by flow regulation and C, O reduced None feasible. n/a n/a n/a n/a downstream water quality. Unannounced inspections at Washing of vehicles, Transit site Take care to avoid least quarterly equipment and outside introduction of new Inspections during supplies before entry Project Area invasive species to, preparation and to Project area of Influence and spread of construction existing invasive phases species within, the Annually, in Abundance/spread of Project area Surveys by summer during invasive alien Project Area through: specialist sub- preparation and species in Project of Influence Introduction/spread - washing of contractor construction area P, C of invasive alien vehicles, equipment phases species. and supplies before Quarterly, during entry to the Project preparation and area; construction - monitoring for Control of Records of phases, and invasive species; new/spreading areas invasive annually Project Area and of invasive alien species afterwards until of Influence - control/eradication species in Project control; any Project- of invasive species area inspections induced spread where found. of invasive species is eliminated Degradation by flow regulation and C, O reduced None feasible. n/a n/a n/a n/a downstream water quality. Take care to avoid Unannounced Schismatogobius introduction of new inspections at tuimanua and Washing of vehicles, Transit site Habitat invasive species to, least quarterly Stenogobius equipment and outside and spread of Inspections during genivittatus Introduction/spread supplies before entry Project Area existing invasive preparation and P, C of invasive alien to Project area of Influence species within, the construction species. Project area phases through: Surveys by Annually, in Abundance/spread of Project Area - washing of specialist sub- summer during invasive alien of Influence vehicles, equipment contractor preparation and

Where is the How is the When is the Environmental Project What parameter is parameter to parameter to parameter to be Institutional Aspect Impact Mitigation action Component phase to be monitored? be be monitored responsibility monitored? monitored? (frequency)? and supplies before species in Project construction entry to the Project area phases area; Quarterly, during - monitoring for preparation and invasive species; construction and Control of Records of phases, and - control/eradication new/spreading areas invasive annually Project Area of invasive species of invasive alien species afterwards until of Influence where found. species in Project control; any Project- area inspections induced spread of invasive species is eliminated Prevention of species' migration C, O upstream of the None feasible. n/a n/a n/a n/a western branch confluence. Unannounced inspections at Washing of vehicles, Transit site Take care to avoid least quarterly equipment and outside introduction of new Inspections during supplies before entry Project Area invasive species to, preparation and to Project area of Influence and spread of construction existing invasive phases species within, the Annually, in Abundance/spread of Aquatic Natural Project area Surveys by summer during Habitat invasive alien Project Area Habitat through: specialist sub- preparation and species in Project of Influence Introduction/spread - washing of contractor construction area P, C of invasive alien vehicles, equipment phases species. and supplies before Quarterly, during entry to the Project preparation and area; construction - monitoring for Control of Records of phases, and invasive species; new/spreading areas invasive annually Project Area and of invasive alien species afterwards until of Influence - control/eradication species in Project control; any Project- of invasive species area inspections induced spread where found. of invasive species is eliminated

Where is the How is the When is the Environmental Project What parameter is parameter to parameter to parameter to be Institutional Aspect Impact Mitigation action Component phase to be monitored? be be monitored responsibility monitored? monitored? (frequency)? All nearby communities Unannounced engaged and Review of inspections understand the legal community quarterly during and practical Project Area Educate local engagement preparation and consequences of people on the records construction introducing invasive dangers of phases species to the deliberate Project reservoir introductions of Unannounced invasive species. Review of inspections No introduction of Project quarterly during invasive species to Project Area incident preparation and the Project reservoir logbook construction phases Restore ≥60.5 Quality Hectares of ≥60.5 Quality Surveys by native forest in at Vaisigano Hectares of native specialist sub- Vegetation least two sites within watershed Annual forest restored contractor clearance; edge the Vaisigano inspections for effects and habitat watershed. first five years of O fragmentation Negligible restoration, then resulting from populations of every five years Control all invasive vegetation invasive species Surveys by until restoration species in the Vaisigano clearance. (particularly rats, cats specialist sub- targets met restoration offset watershed Offset for and pigs) in contractor sites. terrestrial Critical restoration offset Habitat Habitat sites. Permanent flows are Loss of habitat in the Establishment of being maintained of reservoir; prevention At least environmental flows at least 0.3 m3/s from of species' migration Vaisigano Records from annually, during O from the Samasoni the Samasoni weir, upstream of the watershed flow meters operational and middle branch and 0.06 m3/s from power station phase Offset for aquatic weirs. the middle branch (habitat loss). Critical Habitat Habitat weir. Prevention of species' migration Policy and Offset for O upstream of the National institutional support. terrestrial Natural power station Habitat Habitat (habitat loss).

4. 7 References ADB (2009) Safeguard Policy Statement. Asian Development Bank, Manila. ADB (2012) Environmental Safeguards: A Good Practice Sourcebook. Draft Working Document. Asian Development Bank, Manila. Allison, A. & Austin, C.C. (2010) Emoia lawesi. The IUCN Red List of Threatened Species 2010: e.T178528A7564798. http://dx.doi.org/10.2305/IUCN.UK.2010- 4.RLTS.T178528A7564798.en. Allison, A., Hamilton, A., Austin, C.M. & Fisher, R. (2013) Emoia adspersa. The IUCN Red List of Threatened Species 2013: e.T178217A1527142. http://dx.doi.org/10.2305/IUCN.UK.2013-1.RLTS.T178217A1527142.en. Auliya, M., Altherr, S., Ariano-Sanchez, D., Baard, E.H., Brown, C., Brown, R.M., Cantu, J.- C., Gentile, G., Gildenhuys, P., Henningheim, E., Hintzmann, J., Kanari, K., Krvavac, M., Lettink, M., Lippert, J., Luiselli, L., Nilson, G., Nguyen, T.Q., Nijman, V., Parham, J.F., Pasachnik, S.A., Pedrono, M., Rauhaus, A., Córdova, D.R., Sanchez, M.-E., Schepp, U., van Schingen, M., Schneeweiss, N., Segniagbeto, G.H., Somaweera, R., Sy, E.Y., Türkozan, O., Vinke, S., Vinke, T., Vyas, R., Williamson, S. & Ziegler, T. (2016) Trade in live reptiles, its impact on wild populations, and the role of the European market. Biological Conservation 204: 103–119. BBOP (2012) Biodiversity offset design handbook - updated. Business and Biodiversity Offsets Programme (BBOP), Washington, DC, USA. Available at: https://www.forest- trends.org/wp-content/uploads/imported/bbop-biodiversity-odh-final-with-updates-30-6- 2012_final_v1-pdf.pdf BirdLife International (2016) Gymnomyza samoensis. The IUCN Red List of Threatened Species 2016: e.T22704317A93962858. http://dx.doi.org/10.2305/IUCN.UK.2016- 3.RLTS.T22704317A93962858.en. BirdLife International (2018) Didunculus strigirostris (amended version of 2016 assessment). The IUCN Red List of Threatened Species 2018: e.T22691890A129256227. http://dx.doi.org/10.2305/IUCN.UK.2018-2.RLTS.T22691890A129256227.en. BirdLife International (2019a) Endemic Bird Areas factsheet: Samoan Islands. http://datazone.birdlife.org/eba/factsheet/202. BirdLife International (2019b) Important Bird Areas factsheet: Apia Catchments. http://datazone.birdlife.org/site/factsheet/apia-catchments-iba-samoa/text. Bonin, L.M.J. (2008) Ecological restoration project: Mt Vaea Reserve. Consultants Final Report Phase I. Unpublished report to Conservation International Pacific Islands Programme and the Ministry of Natural Resources, Environment and Meteorology. Boseto, D. (2012a) Sicyopterus pugnans. The IUCN Red List of Threatened Species 2012: e.T196368A2450229. http://dx.doi.org/10.2305/IUCN.UK.2012.RLTS.T196368A2450229.en. Boseto, D. (2012b) Stiphodon elegans. The IUCN Red List of Threatened Species 2012: e.T196396A2453196. http://dx.doi.org/10.2305/IUCN.UK.2012.RLTS.T196396A2453196.en. Boseto, D. (2012c) Stiphodon hydroreibatus. The IUCN Red List of Threatened Species 2012: e.T196397A2453341. http://dx.doi.org/10.2305/IUCN.UK.2012.RLTS.T196397A2453341.en. Bristol, R.M., Fraser, I., Groombridge, J.J. & Veríssimo, D. (2014) An economic analysis of species conservation and translocation for island communities: the Seychelles paradise flycatchers as a case study. Journal of Environmental Economics and Policy 3: 237-252. Cowie, R.H., Rundell, R.J. & Yeung, N.W. (2017) Samoan Land Snails and Slugs: An Identification Guide. Department of Marine and Wildlife Resources, American Samoa Government, Pago Pago, American Samoa. DEFRA (2016) Joint action plan to increase the English hen harrier population. Department for Environment, Food & Rural Affairs, Bristol, UK. Entura (2019a) Alaoa Multipurpose Dam Project: Aquatic biodiversity and habitat assessment. Unpublished report to Asian Development Bank. Entura, Cambridge, Tasmania, Australia.

Entura (2019b) Alaoa Multipurpose Dam: Environmental Flow Assessment. Unpublished report to Asian Development Bank. Entura, Cambridge, Tasmania, Australia. Fisher, R., Hamilton, A., Allison, A. & Tallowin, O. (2013) Emoia samoensis. The IUCN Red List of Threatened Species 2013: e.T196618A2467000. http://dx.doi.org/10.2305/IUCN.UK.2013-1.RLTS.T196618A2467000.en. Gardner, T.A., von Hase, A., Brownlie, S., Ekstrom, J.M.M., Pilgrim, J.D., Savy, C.E., Stephens, R.T.T., Treweek, J., Ussher, G T., Ward, G. and ten Kate, K. (2013) Biodiversity offsets and the challenge of achieving no net loss. Conservation Biology 27: 1254-1264. Hoese, D. (2012a) Kuhlia salelea. The IUCN Red List of Threatened Species 2012: e.T196414A2455496. http://dx.doi.org/10.2305/IUCN.UK.2012.RLTS.T196414A2455496.en. Hoese, D. (2012b) Stenogobius genivittatus. The IUCN Red List of Threatened Species 2012: e.T196382A2451568. http://dx.doi.org/10.2305/IUCN.UK.2012.RLTS.T196382A2451568.en. Hoover, J.J., Adams, S.R. & Killgore, K.J. (2003) Can Hydraulic Barriers Stop the Spread of the Round Goby? Aquatic Nuisance Species Research Program Bulletin Volume 3-1. IFC (2007) Environmental, Health, and Safety General Guidelines. International Finance Corporation, Washington DC, USA. IFC (2012) Performance Standard 6: Biodiversity Conservation and Sustainable Management of Living Natural Resources. International Finance Corporation, Washington DC. IFC (2019) Guidance Note 6: Biodiversity Conservation and Sustainable Management of Living Natural Resources. International Finance Corporation, Washington DC. IUCN (2019) The IUCN Red List of Threatened Species. Version 2019-1. Available at: https://www.iucnredlist.org. IUCN SSC (2013) Guidelines for Reintroductions and Other Conservation Translocations. Version 1.0. IUCN Species Survival Commission, Gland, Switzerland. Keith, P., Lord, C. & Larson, H.K. (2017) Review of Schismatogobius (Gobiidae) from Papua New Guinea to Samoa, with description of seven new species. Cybium 41: 45-66. Köhler, F. (2011a) Assiminea similis. The IUCN Red List of Threatened Species 2011: e.T189308A8713908. http://dx.doi.org/10.2305/IUCN.UK.2011-2.RLTS.T189308A8713908.en. Köhler, F. (2011b) Melanoides peregrina. The IUCN Red List of Threatened Species 2011: e.T189614A8755534. http://dx.doi.org/10.2305/IUCN.UK.2011-2.RLTS.T189614A8755534.en. Koneri, R., Saroyo & Tallei, T. E. (2017) Butterfly diversity varies across habitat types in Tangkoko Nature reserve North Sulawesi, Indonesia. Journal of Biodiversity and Environmental Sciences 10: 52-61. Lepidoptera Specialist Group (1996) Euploea algea ssp. schmeltzi. The IUCN Red List of Threatened Species 1996: e.T8351A12907677. http://dx.doi.org/10.2305/IUCN.UK.1996.RLTS.T8351A12907677.en. Lucey, A. (2014) Reintroducing birds of prey cost €1.5 m. Irish Examiner, 9 June 2014. Available at: https://www.irishexaminer.com/ireland/reintroducing-birds-of-prey-cost-15m- 271413.html. MNRE (2006) Recovery plan for the Ma’oma’o or Mao (Gymnomyza samoensis). Samoa’s large forest honeyeater. Ministry of Natural Resources and Environment, Government of Samoa, Apia, Samoa. Mollusc Specialist Group (1996) Thaumatodon hystricelloides. The IUCN Red List of Threatened Species 1996: e.T21717A9313461. http://dx.doi.org/10.2305/IUCN.UK.1996.RLTS.T21717A9313461.en. MRDI (2019) Environmental Impact Assessment. GEO: Batumi Bypass Road Project. Poti- Grigoleti-Kobuleti Bypass: Poti-Grigoleti Road Section (Lot 2, Stage 1). Roads Department of the Ministry of Regional Development and Infrastructure of Georgia, Tblisi. Available at: https://www.adb.org/sites/default/files/project-documents/50064/50064-001-eia-en_3.pdf. MWH (2009) Surface Water Hydrology Technical Assistance: December 2009 Mission. Unpublished report for MNRE; December 2009.

Norbury G., Hutcheon A., Reardon J. & Daigneault, A. (2014) Pest fencing or pest trapping: A bio-economic analysis of cost-effectiveness. Austral Ecology 39: 795–807. Parkes, D., Newell, G. & Cheal, D. (2003) Assessing the quality of native vegetation: the ‘habitat hectares’ approach. Ecological Management and Restoration 4: S29–S38. PIAT (2019) Yellow Crazy Ant Case Studies. Pacific Invasive Ant Toolkit. Available at: http://piat.org.nz/getting-rid-of-ants/management-case-studies/yellow-crazy-ant-management-case- studies. Robertson, P.A., Adriaens, T., Lambin, X., Mill, A., Roy, S., Shuttleworth, C.M. & Sutton‐ Croft, M. (2017) The large‐scale removal of mammalian invasive alien species in Northern Europe. Pest Management Science 73: 273–279. Russell, J.C., Innes, J.G., Brown, P.H. & Byrom, A.E. (2015) Predator-Free New Zealand: Conservation Country. BioScience 65: 520-525. Stirnemann, R. & Taylor-Smith, B. (2019) Proposed Alaoa Dam, Vaisigano River, Upolo, Samoa. Assessment of Ecological Effects: Birds and Bats. Unpublished report to the Asian Development Bank. Tye, A. & Butler, D.J. (2013) Restoration of Nu’utele and Nu’ulua Islands (Aleipata Group), Samoa, through the management of introduced rats and ants. Biodiversity Conservation Lessons Learned Technical Series 13. Conservation International, Apia, Samoa. UNDP (2017) Rare skink, believed on the verge of extinction, found in Niue. https://www.ws.undp.org/content/samoa/en/home/presscenter/pressreleases/2017/08/21/rare- skink-believed-on-the-verge-of-extinction-found-in-niue.html. Whistler, A. & Johnson, D. (1998a) Clinostigma samoense. The IUCN Red List of Threatened Species 1998: e.T38476A10115291. http://dx.doi.org/10.2305/IUCN.UK.1998.RLTS.T38476A10115291.en. Whistler, A. & Johnson, D. (1998b) Drymophloeus samoensis. The IUCN Red List of Threatened Species 1998: e.T38514A10126399. http://dx.doi.org/10.2305/IUCN.UK.1998.RLTS.T38514A10126399.en. Wikramanayake, E., Dinerstein, E., Loucks, C.J., Olson, D.M., Morrison, J., Lamoreux, J., McKnight, M. & Hedao, P. (2002) Terrestrial ecoregions of the Indo-Pacific: a conservation assessment. Island Press, Washington DC, USA. Wildland (2019) Baseline terrestrial invertebrate survey for the Alaoa hydropower dam project, Apia, Samoa. Unpublished report to Entura. Wildland, Te Ngae, Rotorua.

5. Appendix A. Critical and Natural Habitat Assessment The ADB Safeguard Policy Statement (ADB 2009) requires assessment of whether the project is planned in an area that may qualify as Critical Habitat or Natural Habitat. This assessment followed more detailed guidance in International Finance Corporation Performance Standard 6 and its recently-updated accompanying guidance note (IFC 2012, 2019). 5.1 A.1 Areas of analysis Critical Habitat and Natural Habitat assessment ideally takes place across sensible ecological or political units that are sufficiently large to encompass all direct and indirect impacts from the project. These areas of analysis (AoAs) are thus often much broader than the direct project footprint. AoAs may be separate or combined, depending on the ecology of the biodiversity concerned. Given the nature of this Project, it was appropriate to identify two AoAs. Considering the extent of potential impacts on aquatic biodiversity from the Project (Entura 2019b), an aquatic AoA was identified along much of the Vaisigano River, from its outflow into Apia Bay, upstream to the uppermost extents of the east and middle-east branches of the Vaisigano River. The west and middle branches of the Vaisigano River were not included in this aquatic AoA, as they are unlikely to experience any direct negative impacts from the Project. A terrestrial AoA was more challenging to identify. The Vaisigano catchment might be considered appropriate, since it encompasses all areas of potential direct Project impacts. However, the Project is predicted to have population-level impacts on two bird species (Stirnemann & Taylor-Smith 2019), and is situated within a large Key Biodiversity Area that is primarily designated for these species. It thus seems more appropriate, and certainly more precautionary, to use this Apia Catchments KBA as the boundary for the terrestrial AoA for this Project. Identification of both AoAs does not mean that the project has any obligations across them. The aim of this Critical and Natural Habitat Assessment is to identify whether the broad units qualify as Critical Habitat and, if so, for which biodiversity features. This information helps to prioritize impact assessment and to focus mitigation efforts. 5.2 A.2 Assessment of biodiversity which may qualify the area as Critical Habitat Each of the following sections considers candidate Critical Habitat-qualifying biodiversity identified within Entura (2019a), Stirnemann & Taylor-Smith (2019), or other literature as actually or potentially present. In each case, reasons are identified for each biodiversity feature likely meeting or not meeting Critical Habitat. Two categories of biodiversity that might qualify the area as Critical Habitat were only considered briefly here, and will be assessed further by social experts – specifically areas that provide key ecosystem services and areas with biodiversity that has significant social, cultural or economic importance to local communities. These are particularly important categories for consideration in a Samoan context.

A.2.1 Critically Endangered and Endangered species Critically Endangered, Endangered, and (per IFC 2019) Vulnerable species and relevant subspecies were included in an initial screening if they were found during surveys, or there is indication of their presence near the Project site from literature. Threat status is taken from the global IUCN Red List (IUCN 2019). An initial list of 27 such species and subspecies was reduced to nine after a quick screen against quantitative thresholds for Critical Habitat (IFC 2019). The remaining nine are considered in more detail below.

The terrestrial AoA may also be important for the future reintroduction of some highly- threatened species that have been extirpated from Upolo, such as the Endangered Samoan Swallowtail butterfly (Papilio godeffroyi) (Wildland 2019).

Tooth-billed Pigeon (Didunculus strigirostris)

This species, also known as Manumea, is endemic to Samoa and considered globally Critically Endangered (BirdLife International 2018), with less than 250 mature birds believed to be left on Savai’i and Upolo. It has been observed near the Project site (Stirnemann & Taylor-Smith 2019). The Vaisigano catchment and Lake Lanoto’o have been identified as one of only three key sites for the species’ conservation (Stirnemann & Taylor-Smith 2019). The Project terrestrial AoA is based on one of six Key Biodiversity Areas identified for the species, and overlaps >5% of the species’ global Extent of Occurrence (BirdLife International 2018). The species moves seasonally in response to food availability, but the identified priority of the area demonstrates that the Project terrestrial AoA holds >0.5% of the global population of this species, and >5 pairs, at least seasonally. Although it is not clear whether the species breeds in the AoA, this is not directly relevant to Critical Habitat Assessment. As such, Tooth-billed Pigeon qualifies the terrestrial Project area as Critical Habitat.

Mao (Gymnomyza samoensis) This bird species is considered globally Endangered, and is restricted to foothill and montane forest on Savai’i and Upolo (BirdLife International 2016). It has been observed near the Project site (Stirnemann & Taylor-Smith 2019). The Vaisigano catchment is one of six key sites for Mao conservation, one of five sites for Mao conservation on Upolo, and one of five “first priority” sites nationally (Stirnemann & Taylor-Smith 2019). It is one of only three of those key sites with recent records of the species. The Project terrestrial AoA is based on one of five Key Biodiversity Areas identified for the species, and overlaps almost 5% of the species’ global Extent of Occurrence (BirdLife International 2016). Based on this, it is clear that the Project terrestrial AoA holds >0.5% of the global population of this species, and >5 breeding pairs. As such, Mao qualifies the terrestrial Project area as Critical Habitat.

Micronesian Skink (Emoia adspersa) This lizard species is considered globally Endangered, and is known from Savai'i, Upolu and the smaller island Nu'ulua in Samoa, as well as three small islands northeast and northwest of the Samoa group, and one to the southwest (Allison et al. 2013). Its status on some of these small islands is uncertain. It was previously known from Wallis and Futuna and the Cook Islands, but there are no recent records. It is an uncommon coastal forest species, and has been severely impacted on Savai’i by the introduction of Yellow Crazy Ant (Anoplolepis gracilipes), with fragmented remnant subpopulations surviving only in coastal areas and highlands above 500 m altitude. The terrestrial AoA does not include any coastal areas, and is more than 2 km from the coast at all points. As such, it is possible – but unlikely – that the AoA holds a significant proportion of the distribution or population of this species. As such, this species is unlikely to qualify the Project area as Critical Habitat.

Olive Small-scaled Skink (Emoia lawesi) This globally Endangered lizard species occurs in forests of Samoa, American Samoa, Niue and Tonga (Allison & Austin 2010). The terrestrial AoA holds >2% of the global range of this species. It appears to be very rare on Niue, presumably as a result of widespread deforestation (UNDP 2017). Without further information, at least on a precautionary basis, it thus seems likely that the Project terrestrial AoA holds >0.5% of the global population of this species, and >5 breeding animals. As such, it is possible that Olive Small-scaled Skink qualifies the terrestrial Project area as Critical Habitat.

Samoa Skink (Emoia samoensis) This Endangered species is found in forests up to around 1,300 m altitude on both Samoa and American Samoa (Fisher et al. 2013). It was formerly common in lowland areas, but has been extirpated below 500 m in Savai’i as a result of invasion by Yellow Crazy Ants (Paratrechina longicornis). The terrestrial AoA holds >2% of the global range of this species. Without further information, at least on a precautionary basis, it thus seems likely that this AoA holds >0.5%

of the global population of this species, and >5 breeding animals. As such, it is possible that Samoa Skink qualifies the terrestrial Project area as Critical Habitat.

Thaumatodon hystricelloides This snail is considered globally Endangered (Mollusc Specialist Group 1996), and is now only known from high elevations on Upolo (Cowie et al. 2017) – including the Project’s terrestrial AoA (BirdLife International 2019b) and O Le Pupu-Pu’e National Park just to the south-east of (adjoining) this Project’s terrestrial AoA. The AoA represents just over 7% of the land area of Upolo, and holds a disproportionate amount of its higher elevations. It thus seems very likely that the terrestrial AoA holds >0.5% of the global population of this species, and >5 reproducing snails. As such, it is likely that Thaumatodon hystricelloides qualifies the terrestrial Project area as Critical Habitat.

Drymophloeus samoensis This palm species is considered globally Critically Endangered (Whistler & Johnson 1998b). It only occurs in montane cloud forest on Upolo and Savai’i. The terrestrial AoA contains a significant proportion of Upolo’s montane forest. Without further information, it thus seems possible that this AoA holds >0.5% of the global population of this species, and >5 reproducing mature trees. As such, on a precautionary basis, it is possible that Drymophloeus samoensis qualifies the terrestrial Project area as Critical Habitat.

Clinostigma samoense This palm species is considered globally Endangered and is restricted to lowland forests in Upolo (Whistler & Johnson 1998a). It is unclear whether this species occurs in the terrestrial AoA, but it appears likely given that this is one of the largest extents of forest remaining in Upolo. The terrestrial AoA represents just over 7% of the land area of Upolo, and is likely to hold a disproportionate amount of forest. Without further information, it thus seems likely that this AoA holds >0.5% of the global population of this species, and >5 reproducing mature trees. As such, it is likely that Clinostigma samoense qualifies the terrestrial Project area as Critical Habitat.

Euploea algea ssp. schmeltzi Although the whole species has not been assessed for the IUCN Red List, this subspecies of the Long-branded Blue Crow butterfly is considered globally Vulnerable and is restricted to Samoa (Lepidoptera Specialist Group 1996). It was found in the project inundation zone (Wildland 2019), and is likely to occur elsewhere in the terrestrial AoA as E. algea occurs in a range of habitats and is tolerant of forest degradation (Koneri et al. 2017). Assuming an even distribution across the whole of Samoa, the terrestrial AoA would hold c.3% of the global range of this subspecies. There is no reason to suspect that the AoA holds disproportionately high or low populations. The Project only occupies a small percentage of the AoA, and is not predicted to have broad-scale impacts. Without further information, it thus seems unlikely that the Project could have impacts on this butterfly that would impact it to a level that it would become Endangered. As such, Euploea algea ssp. schmeltzi does not qualify the Project area as Critical Habitat.

A.2.2 Endemic or restricted-range species Following the IFC PS6 Guidance Note (IFC 2019), species were considered restricted-range if their global extent of occurrence was 50,000 km2 or less (for terrestrial vertebrates) or, for riverine species, if their global range had less than 500 km linear geographic span. Species were included in an initial screening if they were found during surveys, or there is indication of their presence from literature. An initial list of 50 such species, was reduced to five after a quick screen against quantitative thresholds for Critical Habitat (IFC 2019). Without intra-island information on distribution and abundance, it was assumed that species were evenly

distributed. This meant that the Project’s terrestrial AoA would hold 2-3% of the range of any species endemic to Samoa or the Samoan archipelago, and just over 7% of the range of any species endemic to Upolo. Thus, although a number of restricted-range butterfly and bird species are endemic to Samoa or the broader archipelago (BirdLife International 2019a; Wildland 2019), it is unlikely that the terrestrial AoA holds 10% or more of their range or population, and thus it is unlikely that these restricted-range species qualify this AoA as Critical Habitat. A few more complex species are assessed below.

Salele Flagtail (Kuhlia salelea) This Data Deficient fish species is endemic to Samoa and American Samoa (Hoese 2012a). With a total width of Extent of Occurrence of <100 km and length of <300 km, it is considered a restricted-range species. The Vaisigano watershed represents <5% of its mapped global range (Hoese 2012a) – far less than the 10% threshold guidance given for Critical Habitat by IFC (2019). Given this, Kuhlia salelea does not appear to qualify the Project area as Critical Habitat under Criterion 2.

Schismatogobius tuimanua This fish species is endemic to Samoa and American Samoa (Keith et al. 2017), and found in the lower reaches of the Vaisigano River during recent baseline surveys (William Elvey in litt. 2019). With a total width of Extent of Occurrence of <100 km and length of <300 km, it is considered a restricted-range species. The species has been collected from less than five locations to date, so the Vaisigano River represents >20% of known sites for the species. This rare, recently-described species may well be found in additional sites in future. Until such a time as it is known from more than ten sites (and the Vaisigano River may then not be considered Critical Habitat), on a precautionary basis Schismatogobius tuimanua appears to qualify the Project area as Critical Habitat under Criterion 2.

Stiphodon hydroreibatus This Data Deficient fish species is listed in Entura (2019a) as possibly qualifying the Project area as Critical Habitat as an endemic or restricted-range species. It is known from Samoa, American Samoa and Wallis and Futuna (Boseto 2012c), with an Extent of Occurrence of <100 km width but c.800 km length. As such, based on IFC (2019), it does not qualify as an endemic or restricted-range species. Stiphodon hydroreibatus does not therefore qualify the Project area as Critical Habitat under Criterion 2.

Assiminea similis There is taxonomic uncertainty over whether this snail represents a species, or should be included within A. parvula. If the former, this species should likely be considered globally threatened (Köhler 2011a). Although it was formerly known only from Samoa, American Samoa, Wallis and Futuna, and the Cook Islands, there are only recent records from Upolo. The current known Extent of Occurrence is thus restricted, to c.1,350 km2 (Köhler 2011a). The Project terrestrial AoA represents >6% of the species’ mapped range. However, based on information from A. parvula, this snail is thought to occur on land near to brackish water, thus only in areas outside the terrestrial AoA (Köhler 2011a). Other Assiminea species are amphibious and estuarine (Cowie et al. 2017), so there is a possibility that the species could occur near the coast in the Project aquatic AoA. This is, however, unlikely given degradation and development in that area. Based on the taxonomic uncertainty, <10% of the species’ range overlapping the terrestrial AoA, and low likelihood that suitable habitat exists in the Project area, Assiminea similis does not appear to qualify the Project area as Critical Habitat.

Melanoides peregrina

There is taxonomic uncertainty over whether this freshwater snail represents a valid species. Records have only been attributed to Upolo (Köhler 2011b), which would qualify it as restricted- range (with an Extent of Occurrence width of <50 km and length of <100 km). Assuming it is a valid taxon, and an even distribution across Upolo, the Vaisigano watershed represents c.9 % of its mapped global range – less than the 10% threshold guidance given for Critical Habitat by IFC (2019). There is little information available on this taxon, and nothing that suggests it is likely to occur in the Vaisigano watershed in a higher density than elsewhere in Upolo (in fact, the opposite seems more likely, given the high degradation of rivers in this catchment). Given available information, Melanoides peregrina does not appear to qualify the Project area as Critical Habitat.

A.2.3 Migratory or congregatory species Entura (2019a) lists 15 migratory fish species from Samoa, and 10 migratory crustacean species. These are reviewed rapidly below.

Giant Mottled Eel (Anguilla marmorata), Giant Mottled Eel (Anguilla obscura), Eleotris fusca, Eleotris melanosoma, Rock Flagtail (Kuhlia rupestris), Northern Mud Gudgeon (Ophiocara porocephala) and Red-tailed Goby (Sicyopterus lagocephalus) These fish species are widespread in the Indo-Pacific, and the Project aquatic AoA thus holds considerably less than 1% of each species’ overall distribution. While recognizing that they congregate during migration and breeding, this wide distribution means that the AoA is also unlikely to hold >1% of each species’ population at any point. As such, these species do not qualify the Project area as Critical Habitat.

Polynesian Long-finned Eel (Anguilla megastoma), Ocellated River Goby (Awaous ocellaris), Rainbow Prigi (Hypseleotris cyprinoides/guentheri), These fish species are widespread in the Pacific, and the Project aquatic AoA thus holds considerably less than 1% of each species’ overall distribution. While recognizing that they congregate during migration and breeding, this wide distribution means that the AoA is also unlikely to hold >1% of each species’ population at any point. As such, these species do not qualify the Project area as Critical Habitat.

Schismatogobius tuimanua This fish species is endemic to Samoa and American Samoa, and found in the lower reaches of the Vaisigano River during recent baseline surveys (William Elvey in litt. 2019). Its distribution remains very poorly known, although it is believed to occur only in areas just above tidal influence (Keith et al. 2017). The species has been collected from less than five locations to date, so the Vaisigano River represents >20% of known sites for the species. While this rare, recently-described species may well be found in additional sites in future, it remains likely that the Vaisigano River will represent one of <100 sites for the species, and thus >1% of the species’ range (and, by inference, population). Given this, Schismatogobius tuimanua qualifies the Project area as Critical Habitat under Criterion 3.

Fat-snout Goby (Sicyopterus pugnans) This fish species is known from Samoa and French Polynesia (Entura 2019a). It was recorded during Project baseline surveys in the Vaisigano watershed (Entura 2019a), which represents just over 1% of the species’ overall distribution. On a precautionary basis, in the absence of information about population densities or congregations during migration and breeding, Fat- snout Goby might possibly qualify the Project area as Critical Habitat.

Stenogobius genivittatus

This fish species is known from Samoa, French Polynesia and the Cook Islands (Entura 2019a). It was recorded during Project baseline surveys in the Vaisigano watershed (Entura 2019a), which represents just over 1% of the species’ overall distribution. On a precautionary basis, in the absence of information about population densities or congregations during migration and breeding, Stenogobius genivittatus might possibly qualify the Project area as Critical Habitat.

Green Riffle Goby (Stiphodon elegans) This fish species is known from Samoa, Futuna, French Polynesia and the Cook Islands (Entura 2019a). It was recorded during Project baseline surveys in the Vaisigano watershed (Entura 2019a), which represents just over 1% of the species’ overall distribution. On a precautionary basis, in the absence of information about population densities or congregation during migration and breeding, Green Riffle Goby might possibly qualify the Project area as Critical Habitat.

Stiphodon hydroreibatus This fish species is known from Samoa, American Samoa and Futuna (Entura 2019a). It was recorded during Project baseline surveys in the Vaisigano watershed (Entura 2019a), which represents over 3% of the species’ overall distribution. On a precautionary basis, in the absence of information about population densities or congregation during migration and breeding, Stiphodon hydroreibatus might possibly qualify the Project area as Critical Habitat.

Noumea River Prawn (Macrobrachium aemulum), Koua River Prawn (Macrobrachium australe), Giant Jungle Prawn (Macrobrachium lar) and Mountain River Prawn (Macrobrachium latimanus), These crustacean species are widespread in the Indo-Pacific, and the Project aquatic AoA thus holds considerably less than 1% of each species’ overall distribution. While recognizing that they congregate during migration and breeding, this wide distribution means that the AoA is also unlikely to hold >1% of each species’ population at any point. As such, these species do not qualify the Project area as Critical Habitat.

Green Lace Shrimp (Atyoida pilipes), Bamboo Shrimp (Atyoida spinipes), Berit River Prawn (Macrobrachium bariense), Lollipop Prawn (Macrobrachium gracilirostre), Scissor River Prawn (Macrobrachium latidactylus) and Peaceful Prawn (Macrobrachium placidum) These crustacean species are widespread in the Pacific, and the Project aquatic AoA thus holds considerably less than 1% of each species’ overall distribution. While recognizing that they congregate during migration and breeding, this wide distribution means that the AoA is also unlikely to hold >1% of each species’ population at any point. As such, these species do not qualify the Project area as Critical Habitat.

A.2.4 Unique assemblages of species that are associated with key evolutionary processes As is the case for the majority of Pacific islands, the Samoan Archipelago has been subject to long and extreme isolation that has allowed evolutionary processes to generate unique, endemic flora and fauna. For example, about 28% of the flowering plants are endemic. Beyond this general context, however, there is no reason to believe that the terrestrial or aquatic AoA host particularly unusual or key evolutionary processes. Many of the archipelago’s plants are

restricted to single islands (Wikramanayake et al. 2002), but there is very limited intra-island endemism. Unique assemblages of species associated with key evolutionary processes thus do not qualify the Project area as Critical Habitat. A.2.5 Areas having biodiversity of significant social, economic, or cultural importance to local communities (including ecosystem services) The available documents present very limited information on ecosystem services or other values to local communities. Most information presented relates to provisioning services. Entura (2019a) states that ‘Fishing in the river for eels and prawns is a recreational activity only’ and ‘…fishing for crustaceans appears to be limited to a recreational activity only and the reaches upstream of the proposed dam, while not completely inaccessible, are probably fished very rarely…’. Stirnemann & Taylor-Smith (2019) refer to hunting near to the Project site and note the cultural significance of Tooth-billed Pigeon, as it is the national bird. The limited information presented does not give reason to believe that the Project terrestrial or aquatic AoA are sufficiently important to local people that they represent Critical Habitat under this criterion. However, it is beyond the scope of this assessment to collect additional information on ecosystem services, and then to assess which may qualify the project area as Critical Habitat. A.2.6 Legally protected areas and international recognized areas There are no protected areas near to the Project. The nearest is Mount Vaea Scenic Reserve, approximately 3 km to the north (Stirnemann & Taylor-Smith 2019), while the O le Pupu Pue National Park directly adjoins the Project terrestrial AoA some way to the south of the Project. The internationally recognized Apia Catchments Important Bird Area (de facto also a Key Biodiversity Area) overlaps the Project and is used as its terrestrial AoA (BirdLife International 2019b), with its boundary loosely based on remaining forests in those catchments. This IBA is of particular importance for Tooth-billed Pigeon and Mao. Following IFC (2019), the Apia Catchments Key Biodiversity Area qualifies the Project area as Critical Habitat, since it is an internationally recognized area of high biodiversity value that meets thresholds for Critical Habitat for some species for which it was designated (Section A.2.1). A.2.7 Summary The Project’s terrestrial Area of Analysis qualifies as Critical Habitat, owing to the presence of several Critical Habitat-qualifying threatened species at globally significant levels and the presence of an internationally-recognized area. The Project’s terrestrial Area of Analysis qualifies as Critical Habitat, owing to the presence of several Critical Habitat-qualifying restricted-range and migratory fish species at globally significant levels. 5.3 A.3 Assessment of Natural Habitat Only qualitative information is currently available on the extent of Natural Habitat at the Project site. Wildland (2019) notes that 2-3 ha of patchy forest dominated by indigenous plant species, and with largely intact ecological function, occur on the lower hillslopes and river terraces within the inundation zone, and considers these Natural Habitat. R. Stirnemann (in litt. 2019) notes that even degraded secondary forest remains of value for breeding and feeding to species such as Tooth-billed Pigeon and Mao, and so can be considered Natural Habitat in that context. Wildland (2019) also notes the difficulty of remote identification and quantification of Natural Habitat in Samoa, given the prevalence of non-native tree species which are difficult to identify from remotely sensed imagery. Quantification of terrestrial Natural and Modified Habitat in the Project’s area of influence will require site visits. As such, on a precautionary basis, all forest is currently considered Natural Habitat. Without extensive surveys across the terrestrial AoA, such as those conducted by Stirnemann and Taylor-Smith (2019), it is also not possible to identify all sites which may hold globally- significant populations of Critical Habitat-qualifying species, so it is not possible to map terrestrial Critical Habitat at a fine scale. On a precautionary basis, in the absence of fine-

scale distribution data for biodiversity, all terrestrial Natural Habitat may also qualify as Critical Habitat. Entura (2019a) presents a useful written assessment of Natural and Modified Habitat in the Project area. This is depicted graphically here in Figure 2. Two stretches of Modified Habitat are identified: (i) the lower Vaisigano River from Samasoni weir to its discharge into Apia Bay, owing to the impacts of flow extraction, the absence of an environmental flow and urban impacts; (ii) the middle branch upstream of Samasoni weir to the junction of the middle-east and east branches, due to flow regulation, the presence of small weirs, and riparian impacts from urban development and garden planting; and (iii) the east branch upstream of the junction with the middle-east branch to the Fale ole Fee offtake, due to the offtake resulting in zero flow through this reach for extended periods of the year (Entura 2019a). Other stretches have also been significantly impacted, such as the middle-east branch between the Alaoa offtake weir and power station, but not to the extent that their primary ecological functions have been substantially modified. Therefore, these other stretches are considered Natural Habitat (Figure 2).

Figure 2. Schematic of aquatic Area of Analysis, showing areas of Critical, Natural and Modified Habitat, and any Critical Habitat-qualifying fish species present in each stretch