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Maximising conservation impact by prioritising islands for biosecurity
Available Online

Bambini, L.

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Dawson, J.

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Havery, S.

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John, L.

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Oppel, S.

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Radford, E.

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Varnham, K.

2019
Invasive alien species are one of the primary threats to native biodiversity on islands worldwide, and their expansion continues due to global trade and travel. Preventing the arrival and establishment of highly successful invasive species through rigorous biosecurity is known to be more economic than the removal of these species once they have established. However, many islands around the world lack biosecurity regulations or practical measures and establishing biosecurity will require social and financial investments. Guiding these investments towards islands where native biodiversity is at highest risk from potential invasions is of strategic importance to maximise conservation benefit with limited resources. Here we implement an established prioritisation approach, previously used to identify which islands will have the greatest conservation gains from the eradication of invasive species, to identify which islands would benefit the most from establishing or improving biosecurity. We demonstrate this approach for 318 islands in the Caribbean UK Overseas Territories and Bermuda where we considered all threatened native terrestrial vertebrates that are vulnerable to the most harmful invasive vertebrates (black and brown rats, cats, small Indian mongoose, green iguana). The approach calculates the increase in conservation threat score resulting from anticipated negative effects of potential invaders on native biodiversity, and highlighted Sombrero (Anguilla) and Cayman Brac (Cayman Islands) as important islands where threatened reptile species would likely be eliminated if rats, feral cats or mongoose invaded. Feasibility and cost implications should now be investigated more closely on the highlighted islands. The prioritisation presented here can be expanded to more islands and more invasive/native taxa (herbivores, plants and invertebrates), but requires a classification of the severity of potential impacts between invasive and native species for which currently little information exists. Besides highlighting opportunities for biosecurity, this approach also highlights where knowledge gaps about population sizes of and threats to reptiles with restricted ranges exist.
A little goes a long way when controlling invasive plants for biodiversity conservation
Available Online

Dudley, T.

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Knapp, D.

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Knapp, J.

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Stahlheber, K.

2019
Invasive species, particularly animals, are being eradicated from islands at ever more ambitious scales. In order to protect island biodiversity and the essential ecosystem functions that it provides, however, plant invasions should be given more management attention. While many advances have been made, plant eradication is inherently more difficult than animal eradication due to persistent seed banks, and eradication may not be possible for more extensive populations. While maintenance control has been successful, critics question the sustainability and priority of these efforts, and targets vary widely. Developing consistent and informed targets requires an understanding of how biodiversity varies with invader cover, yet little is known about this topic. Our research suggests that limited control efforts may be highly beneficial. We conducted a meta-analysis of 54 studies to investigate the effects of plant invasions on invertebrate diversity, incorporating invader cover and residence time as potential causal mechanisms. We also contrasted restored plots with otherwise native plots. We found that invertebrate species richness was 31% lower in exotic plots than in native plots, and that there is a threshold at around 70% invader cover after which the negative effects are significant across all studies. Furthermore, these negative effects tended to decrease with time, and invertebrate richness was even greater in restored plots. The implication is that by removing 30% or less of invasive plant cover and restoring natives, we can achieve many of our conservation goals. We argue that by maintaining invasive patches at or below 70% exotic cover at a site in the near term, we can buy time for both the islands’ insect herbivores to adapt to use the invader, and for managers to continue improving plant eradication technologies. By retaining native diversity in this way, we can help to increase the resistance and resilience of these systems to global change and other stressors.
Achieving large scale, long-term invasive American mink control in northern Scotland despite short term funding
Available Online

Horrill, J.

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Lambin, X.

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Raynor, R.

2019
The American mink (Neovison vison) has invaded most of the United Kingdom following escapes from furfarms over decades. Its escalating impact on riparian and coastal biodiversity, including seabirds and water voles, is well documented. Starting in north-east Scotland in 2004, long-term, multi-institution mink control efforts have harnessed the enthusiasm of volunteer conservationists to push back the mink invasion over a vast area. Rather than the outcome of a single project with secured long-term funding, this achievement resulted from four successive joined up projects each with short-term funding. The beginnings of the project (2004–2006), under the auspices of the north-east Scotland Biodiversity Partnership were small scale (30 km2) and centred upon a lowland remnant water vole meta-population. Mink control efforts were scaled-up to 6,000 km2 of mostly marginal mink habitat as part of the Cairngorms Water Vole Conservation Project (2006–2009) centred on the newly established Cairngorms National Park. The project, led by the University of Aberdeen, was funded by a charity, a UK Research council and Scottish Natural Heritage and involved the national park authority, and three local fisheries trusts. The approach was to deploy a “rolling carpet” of mink control based on the use of mink rafts operated by volunteers and that facilitated mink detection and removal. Substantial funding was then secured for a successor project, the Scottish Mink Initiative (2010–2014) involving, all previous partners plus 14 local fisheries trusts coordinated by the Rivers and Fisheries Trusts of Scotland. Mink were pushed back over a vast area (29,000 km2) and their spread in coastal areas of north-west Scotland was countered. After a period with minimal bridge funding, coordinated mink control efforts resumed, thanks to the newly funded Scottish Invasive Species Initiative (2017–2021) seeking to extend the approach used with mink to other riparian invasives. Mink remain scarce or absent and water voles are recovering spectacularly. Coordinated mink control delivered tangible conservation benefits and improved understanding of the socio-ecological system despite the challenges of short-term funding.
Going to scale: reviewing where we’ve been and where we need to go in invasive vertebrate eradications
Available Online

Hagen, E.

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Holmes, N.

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Howald, G.

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Keitt, B.

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Poiani, K.

2019
We are on the edge of the sixth mass extinction on Earth. Islands represent ca. 5% of the earth’s land area yet are home to 61% of extinctions in the past 500 years, and currently support 39% of critically endangered species. Invasive species are a leading cause of extinction and endangerment on islands. Invasive vertebrates, particularly mammals, are among some of the most damaging invasive species on islands. Eradicating invasive mammals is an increasingly utilised conservation tool. Nevertheless, conservation intervention needs greatly outstrip the island restoration community’s capacity. There are thousands of islands where invasive vertebrates are driving species toward extinction. So, how can the effort be matched to the scale of the problem? One approach is to improve outreach and communications to increase the resources available for projects. There are great stories; but these need to be told compellingly and repeatedly. Increasing social acceptance and support for invasive species eradications will reduce project costs associated with stakeholder engagement. Broadening the funding base can be accomplished by building stronger cost benefit valuations as well as engaging funders of climate change, marine conservation, human wellbeing, and food security. Furthermore, it is important to build upon existing partnerships to create or grow coalitions that can access these resources as part of broader, holistic efforts to address multiple conservation issues.
Tackling invasive non-native species in the UK Overseas Territories
Available Online

Key, G.

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Moore, N.

2019
The 16 UK Overseas Territories (OTs) together account for 94% of the UK’s unique biodiversity and make a significant contribution to global biodiversity. Being predominantly islands, the OTs are very vulnerable to the introduction of potentially harmful invasive non-native species, and pressures are increasing with the continual growth of international trade and impact of climate change. Biosecurity is acknowledged as the most cost-effective means of addressing invasive species threats for small islands, and yet the OTs face many challenges in the implementation of biosecurity controls. In 2016 a UK Government funded project “Tackling Invasive Non-Native Species in the UK Overseas Territories” was initiated to improve the biosecurity of the OTs against non-native species in order to improve their environmental resilience and food security through technical assistance and capacity building. A gap analysis carried out in early 2017 assessed the strengths and weaknesses for all 16 OTs along the biosecurity continuum in three areas: (1) prevention (2) early warning and rapid response, and (3) long-term management. Overall, capacity is weakest in the area of prevention and greatest in that of long-term management. Border activities, where implemented, are primarily linked to agricultural production and animal health. Few OTs have carried out horizon scanning or comprehensive pathway analysis or have the capacity to carry out pest risk analysis. Greatest capacity is seen in the relatively well-resourced Antarctic and sub-Antarctic territories, and in St Helena Island which was the subject of a 4-year project in anticipation of air access. Legislation is generally weak, and few OTs have developed territorial biosecurity policies or strategies. Officers responsible for biosecurity often have a range of functions in addition to their biosecurity roles, lack access to specialist expertise and diagnostic facilities, and may also lack access to appropriate training. This compromises their ability to deliver effective biosecurity. This situation is common to many small island states.
No detection of brodifacoum residues in the marine and terrestrial food web three years after rat eradication at Palmyra Atoll, Central Pacific
Available Online

Holmes, N.

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Howald, G.

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Shiels, A.

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Wegmann, A.

2019
Invasive alien species represent one of the greatest threats to native plants and animals on islands. Rats (Rattus spp.) have invaded most of the world’s oceanic islands, causing lasting or irreversible damage to ecosystems and biodiversity. To counter this threat, techniques to eradicate invasive rats from islands have been developed and applied across the globe. Eradication of alien rats from large or complex island ecosystems has only been successful with the use of bait containing a rodenticide. While effective at eradicating rats from islands, rodenticide can persist in the ecosystem longer than the time required to eradicate the target rat population and can potentially harm non-target species. However, the persistence of rodenticides in ecosystems following rat eradication campaigns is poorly understood, though predictions can be made based on the chemical properties of the rodenticide and the environment it is applied in. Brodifacoum, a relatively persistent second-generation anticoagulant, was used to successfully eradicate rats from Palmyra Atoll. With this study, we evaluated the persistence of brodifacoum residues in terrestrial and marine species at Palmyra Atoll (Northern Line Islands) three years after rat eradication. We collected 44 pooled samples containing 121 individuals of the following: mullet (Moolgarda engeli), cockroaches (Periplaneta sp.), geckos (Lepidodactylus lugubris), hermit crabs (Coenobita perlatus), and fiddler crabs (Uca tetragonon). Despite detection of brodifacoum residue in all five of the species sampled in this study 60 days after the application of bait to Palmyra Atoll in 2011, brodifacoum residue was not found in any of the pooled samples collected three years after bait application. Our study demonstrates how brodifacoum residues are unlikely to persist in the marine and terrestrial food web, in a wet tropical environment, three years after rat eradication.