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Results Forum News 35 article: Developing a plan for Pacific rat eradication on Henderson Island Purpose A Plan for Pacific Rat eradication on Henderson Island is agreed among experts and stakeholders. Invasive alien species are the main current threat to the biodiversity of the UK OT's. Rats Rattus spp.are the most widespread island invaders in the world, and are responsible for more extinctions in historic times than any other species except humans. Henderson Island is a 37 km2 raised atoll in the South Pacific. It is one of the least anthropogenically modified islands of its size in the world, being uninhabited, and supporting undisturbed native vegetation communities and remarkably few invasive alien species. Consequently, it is a natural World Heritage Site, one of two in the UK OT's. The island is known to support several tens of endemic invertebrate species, nine endemic higher plant species and four endemic land-bird species. There are 15 globally threatened flowering plant taxa, and six bird taxa. It is therefore an Alliance for Zero Extinction Site, one of seven such in the UK OT's. The one major problem currently affecting Henderson's biodiversity is the presence of invasive alien Pacific Rats Rattus exulans, which are abundant throughout the island. Evidence from fieldwork in 1991 and 2003 shows that rats depredate the chicks of Pterodroma petrels to such an extent that their productivity must be extremely low. Preliminary population modelling indicates that the birds cannot sustain such levels of depredation, and that their populations are probably in long-term decline (see Varnham review). Henderson is one of the world headquarters for this group of species: the endangered endemic Henderson Petrel, Kermadec Petrel, Herald Petrel and Murphy's Petrel all occur in populations exceeding 1,000 pairs. The globally endangered Phoenix Petrel also occurred early in the twentieth century, but appears to have been extirpated, presumably by rats. Prior to the arrival of Polynesians and the introduction of rats, populations of seabirds on Henderson were at least an order of magnitude higher than they are currently.Elsewhere in its range, the Pacific Rat is known to have considerable effects on plant communities, by reducing recruitment of some plant species, and to reduce populations of some large invertebrates. It is highly likely that such effects are occurring on Henderson, but they have not been studied. Among the UK OT's, the major islands on which rodents are thought to have devastated globally important biodiversity, and where eradication is a plausible option (due to lack of a large human population) are Tristan da Cunha, Gough, and Henderson. OTEP-funded feasibility studies are in production for the former two, and an Operational Plan is in production for Tristan. It therefore makes sense to conduct such a project for Henderson within the same time-frame. This will give decision-makers the ability to weigh the costs and benefits of these three ambitious island restoration concepts together, and allow practitioners the options to prioritise and follow up funding opportunities effectively. In particular, it seems likely that Henderson would be somewhat cheaper (because smaller) and more straightforward (because it holds rats not mice, and is uninhabited) than the other two. Experience with the Tristan and Gough projects, and discussion with leading eradication experts, indicates that an expensive and difficult site visit by an eradication consultant would not be necessary to produce an authoritative feasibility study for Henderson: it will be sufficient for an expert on the island to meet at length with an eradication expert, as proposed here. For such large restoration programmes, the process of producing a Feasibility Study, followed by an Operational Plan (where the feasibility study is positive) prior to commencing fundraising and (where appropriate) a call for tenders is an established and successful template. It ensures that the programme has full support, is carefully and authoritatively justified, and does not take place without due planning. RSPB is the UK partner of BirdLife International. BirdLife International's Pacific program has been running for two years now, and is focusing on restoring islands in Polynesia and Melanesia. This Henderson project will be able to make strong links to these regional initiatives, sharing experience with similar environments and species, and possibly in the long-term, combining efforts in eradication programmes, to produce economies of scale (e.g. in bait shipments, helicopter hire). The Henderson project will also benefit from the rapid increase in interest in Pacific island restoration among the conservation and donor community. Outputs - 50 colour hard copies of a Feasibility Study, endorsed by independent experts, describing:
- The technical feasibility of eradicating rats from Henderson
- The impact of eradicating rats from Henderson on the island's biodiversity value
- Preferred methods, main challenges (including non-target impacts), logistical options and necessary prior steps to an eradication
- First-pass estimate of the costs of an eradication. - Operational Plan for the eradication of Pacific Rats from Henderson Island published, describing the nature of and requirements for:
- Pre-eradication actions, project team, baits, ship support, helicopters, bait-sowing operations, planning, logistical operations, health & environmental issues, contingencies, post-operation actions, risk assessment, workplan & timeframe, and budget. - Scientific paper submitted, describing the effects of rats on petrel species on Henderson Island.
Main Activities See Annex II, Workplan - Evaluate the conservation benefit of eradicating Pacific Rats from Henderson.
A Review of the Impacts of Pacific Rats on the biota of Henderson, and the conservation benefits of an eradication, will be produced as a desk-study led by Dr Brooke and Dr Hilton. As part of this, a scientific paper describing the impacts of rats on Henderson's seabirds, and the effects of removing rats on their status will be written, in collaboration with Dr Norman Ratcliffe, an RSPB population biologist. - Evaluate the feasibility of eradicating rats from Henderson.
The main Feasibility Assessment will be developed at a ca.5-day meeting between Dr Mike Brooke, the leading expert on the island's biota, environment and logistics, and a recognised eradication expert (to be identified). - Combine (1) and (2) to produce a feasibility study and cost: benefit analysis.
The Review of the Impacts and the Feasibility Assessment will be synthesised into a single Feasibility Study document, which will be circulated for comment among stakeholders, and peer-reviewed by the Invasive Species Specialist Group / Island Eradication Advisory Group. When endorsement has been received, and any requested modifications made, the Feasibility Study will be published as a single document in hard copy and pdf. - If the feasibility study is positive, produce an Operational Plan for the eradication of Pacific Rats from Henderson.
The Operational Plan will be produced following the Feasibility Study, and will be similarly circulated for comment, peer-reviewed, and published.
Stakeholder Analysis - Pitcairn Island government and community:
The Conservation Officer and Mayor of Pitcairn has been consulted about the project proposal, and has expressed his strong support and enthusiasm for the idea. - The Henderson Island Management Committee:
This Committee is responsible for implementing the FCO-agreed Henderson Management Plan and co-ordinating conservation management of the island. The Committee has been consulted about the project proposal, and has written to express its support. - Other biodiversity conservation agencies/people with an interest in the island & its species:
We have contacted Dr Steve Waldren, University of Dublin and Noeleen Smyth, BEC Consultants who have conducted recent plant conservation work and led the production of the Pitcairn Environment Management Plan. They have emailed their support for the project.We have also discussed the project with the BirdLife International Pacific Regional Office and the BirdLife International Seabird Campaign, both of whom have expressed their strong support.
These stakeholders will form the basis for a communication and consultation group as the project is implemented, and will be asked to comment and endorse the final Feasibility Study.Critical Assumptions Risk : Suitable consultant cannot be found.
Probability : Very Low
Impact: Very High
Management: Good personal contacts between Dr Hilton & invasive species specialists in New Zealand Wider Significance Prior to a rat eradication taking place, and in order to put together a successful funding bid and call for tenders, an authoritative, peer-reviewed feasibility study and Operational Plan by acknowledged experts is a critical step. This is the standard pattern adopted in most major island restoration projects. This project will deliver these steps, and therefore facilitate the development of an eradication programme. Removing rats from Henderson Island would complete the single major activity required to restore the World Heritage Site to an almost pristine state. It would prevent extirpation of several globally important seabird populations, and result in their immediate recovery. It would be by far the major rodent eradication to take place outside New Zealand to date, and would signal UK and the OTs' intentions to undertake ambitious, high-profile restorations of their globally important islands. It would make a major contribution to the UK meeting its obligations under the CBD and World Heritage Conventions. Other Information Funded by FCO/DIFD Overseas Territories Environment Programme, 2007, project number, PIT401 Multilateral Environmental Agreements Henderson is a natural World Heritage Site, one of two such in the UK OT's. The other, Gough, also has as its major conservation issue the presence of introduced rodents. As part of the World Heritage inscription, a Management Plan must be adopted. The Henderson Management Plan has as an objective "to control or eradicate, where necessary and feasible, alien species that are already at Henderson Island." and notes that priority should be given to those species with greatest impact. The project will help Pitcairn in meeting Article 8 (in-situ conservation) of the Convention on Biological Diversity, although this MEA has not yet been extended to Pitcairn. Actions to address invasive alien species are a 'cross-cutting issue' for the CBD and island biodiversity is one of seven 'thematic programmes'. A rat eradication on Henderson Island would reverse the loss of biodiversity on Henderson, and thus assist with meeting the 2010 biodiversity target. The project will assist Pitcairn in meeting requirements under the Environment Charter. Pitcairn's commitments include 'ensure the protection and restoration of key habitats, species, and landscape features' and 'attempt the control and eradication of invasive species'. The UK government commitments include to 'promote' sharing of experience and expertise between Pitcairn, other Overseas Territories, and small island states and communities which share similar environmental problems. and "use UK, regional and local expertise to give advice and improve knowledge of technical and scientific issues". The draft "Pitcairn Islands Environment Management Plan" has as an objective: Funding sought to examine feasibility of increasing and continuing rat eradication efforts on Henderson.
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