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Invasive species pose an enormous threat in the Pacific: not only do they strongly affect biodiversity, but they also potentially affect the economic, social, and cultural wellbeing of Pacific peoples. Invasive species can potentially be managed and that their impacts can potentially be avoided, eliminated, or reduced. However, neither the costs nor the numerous benefits of management are well understood in the Pacific. Thus, the goals of this project were: A) to account for both the costs and benefits of managing invasive species; B) to prepare empirically grounded advocacy materials to help increase investment in the management of invasive species; C) to help governments prioritise investment in managing these species; and D) to build capability for undertaking economic assessments in the future. To accomplish these goals, we undertook cost-benefit analyses (CBAs) of managing five species that are well established on Viti Levu, Fiji: spathodea campanulata (African tulip tree), herpestus javanicus (small Asian mongoose), papuana uninodis (taro beetle), pycnonotus cafer (red-vented bulbul), and merremia peltata (merremia vine). Next, we conducted a comprehensive training programme on the CBA for invasive species management for professionals from the Pacific. Third, we collaborated with Pacific organisations to develop a uniform guide to conducting CBAs with numerous examples from the region. We also designed a flexible Microsoft Excel-based tool for conducting CBAs, enabling professionals who did not attend the training course to nevertheless undertake rigorous CBAs on invasive spsecies management. Finally, we developed advocacy material and publicised findings from this project to promote investment in invasive species management. This report details these activities in turn. It also includes numerous appendices that include the tools, guidance documents, and advocacy materials developed under this project.

Invasive alien mammals are the major driver of biodiversity loss and ecosystem degradation on islands. Over the past three decades, invasive mammal eradication from islands has become one of society's most powerful tools for preventing extinction of insular endemics and restoring insular ecosystems. As practitioners tackle larger islands for restoration, three factors will heavily influence success and outcomes: the degree of local support, the ability to mitigate for non-target impacts, and the ability to eradicate non-native species more cost-effectively. Investments in removing invasive species, however, must be weighed against the risk of reintroduction. One way to reduce reintroduction risks is to eradicate the target invasive species from an entire archipelago, and thus eliminate readily available sources. We illustrate the costs and benefits of this approach with the efforts to remove invasive goats from the Galápagos Islands. Project Isabela, the world's largest island restoration effort to date, removed > 140,000 goats from > 500,000 ha for a cost of US$10.5 million. Leveraging the capacity built during Project Isabela, and given that goat reintroductions have been common over the past decade, we implemented an archipelago-wide goat eradication strategy. Feral goats remain on three islands in the archipelago, and removal efforts are underway. Efforts on the Galápagos Islands demonstrate that for some species, island size is no longer the limiting factor with respect to eradication. Rather, bureaucratic processes, financing, political will, and stakeholder approval appear to be the new challenges. Eradication efforts have delivered a suite of biodiversity benefits that are in the process of revealing themselves. The costs of rectifying intentional reintroductions are high in terms of financial and human resources. Reducing the archipelago-wide goat density to low levels is a technical approach to reducing reintroduction risk in the short-term, and is being complemented with a longer-term social approach focused on education and governance.

New Zealand, an archipelago of more than 2000 islands, has a terrestrial fauna especially depauperate in native land mammals. Kiore (Rattus exulans) was the first of four rodent species introduced by people. A project to eradicate invasive rats from Kapiti Island in 1996, represented a turning point in the technology, complexity and scale at which managers of natural heritage on New Zealand islands could operate. This paper includes case studies of some significant projects targeting rodents, sometimes with other introduced mammals, undertaken in the 12 years following Kapiti. Details of the methods, costs, results and outcomes are provided for Kapiti, Whenua Hou, Tuhua, Campbell, Raoul, Hauturu, Taukihepa, and Pomona islands, collectively representing a total of over 23,000 ha of habitat cleared of introduced mammals. Research and trials undertaken in the Kapiti project provided the basis for future environmental risk assessments, allowing other projects to focus on knowledge gaps. New trends in invasive species eradication in New Zealand include more challenging multi-species eradication projects, some of which are undertaken by self- funded community groups. To summarise the lessons of the New Zealand experience: a programmatic approach is recommended which will fit each eradication within a context or framework of goals for those islands; address biosecurity issues at the outset; build capability to attempt the most challenging and rewarding projects; facilitate investment in monitoring and manage expectations of stakeholders to ensure their ongoing support. Success breeds success but is never guaranteed.