Nick D. Holmes

Invasive mammal eradication on islands results in substantial conservation gains.

Significance Global conservation actions to prevent or slow extinctions and protect biodiversity are costly. However, few conservation actions have been evaluated for their efficacy globally, hampering the prioritization of conservation actions. Islands are key areas for biodiversity conservation because they are home to more than 15% of terrestrial species and more than one-third of critically endangered species; nearly two-thirds of recent extinctions were of island species. This research quantifies the benefits to native island fauna of removing invasive mammals from islands. Our results highlight the importance of this conservation measure for protecting the worlds most threatened species. More than US

Eradicating multiple invasive species on inhabited islands: The next big step in island restoration?

21 billion is spent annually on biodiversity conservation. Despite their importance for preventing or slowing extinctions and preserving biodiversity, conservation interventions are rarely assessed systematically for their global impact. Islands house a disproportionately higher amount of biodiversity compared with mainlands, much of which is highly threatened with extinction. Indeed, island species make up nearly two-thirds of recent extinctions. Islands therefore are critical targets of conservation. We used an extensive literature and database review paired with expert interviews to estimate the global benefits of an increasingly used conservation action to stem biodiversity loss: eradication of invasive mammals on islands. We found 236 native terrestrial insular faunal species (596 populations) that benefitted through positive demographic and/or distributional responses from 251 eradications of invasive mammals on 181 islands. Seven native species (eight populations) were negatively impacted by invasive mammal eradication. Four threatened species had their International Union for the Conservation of Nature (IUCN) Red List extinction-risk categories reduced as a direct result of invasive mammal eradication, and no species moved to a higher extinction-risk category. We predict that 107 highly threatened birds, mammals, and reptiles on the IUCN Red List—6% of all these highly threatened species—likely have benefitted from invasive mammal eradications on islands. Because monitoring of eradication outcomes is sporadic and limited, the impacts of global eradications are likely greater than we report here. Our results highlight the importance of invasive mammal eradication on islands for protecting the worlds most imperiled fauna.

Prioritizing Islands for the Eradication of Invasive Vertebrates in the United Kingdom Overseas Territories

Invasive species are the greatest threat to island ecosystems, which harbour nearly half the world’s endangered biodiversity. However, eradication is more feasible on islands than on continents. We present a global analysis of 1,224 successful eradications of invasive plants and animals on 808 islands. Most involve single vertebrate species on uninhabited islands, but plant and invertebrate eradications occur more often on inhabited islands. Inhabited islands are often highly modified and support numerous introduced species. Consequently, targeting a single invasive species can be ineffective or counterproductive. The impacts of other pests will continue and, in some cases, be exacerbated. The presence of people also creates regulatory, logistical and socio-political constraints. Real or perceived health risks to inhabitants, pets and livestock may restrict the use of some eradication tools, and communities or individuals sometimes oppose eradication. Despite such challenges, managing invasive species is vital to conserve and restore the unique biodiversity of many inhabited islands, and to maintain or improve the welfare and livelihoods of island residents. We present a brief case study of the Juan Fernández Archipelago, Chile, and discuss the feasibility of eradicating large suites of invasive plants and animals from inhabited islands while managing other invaders for which eradication is not feasible or desirable. Eradications must be planned to account for species interactions. Monitoring and contingency plans must detect and address any ‘surprise effects’. Above all, it is important that the local community derives social, cultural and/or economic benefits, and that people support and are engaged in the restoration effort.

Behaviour and breeding success of gentoo penguins Pygoscelis papua in areas of low and high human activity

Invasive alien species are one of the primary threats to native biodiversity on islands worldwide. Consequently, eradicating invasive species from islands has become a mainstream conservation practice. Deciding which islands have the highest priority for eradication is of strategic importance to allocate limited resources to achieve maximum conservation benefit. Previous island prioritizations focused either on a narrow set of native species or on a small geographic area. We devised a prioritization approach that incorporates all threatened native terrestrial vertebrates and all invasive terrestrial vertebrates occurring on 11 U.K. overseas territories, which comprise over 2000 islands ranging from the sub-Antarctic to the tropics. Our approach includes eradication feasibility and distinguishes between the potential and realistic conservation value of an eradication, which reflects the benefit that would accrue following eradication of either all invasive species or only those species for which eradication techniques currently exist. We identified the top 25 priority islands for invasive species eradication that together would benefit extant populations of 155 native species including 45 globally threatened species. The 5 most valuable islands included the 2 World Heritage islands Gough (South Atlantic) and Henderson (South Pacific) that feature unique seabird colonies, and Anegada, Little Cayman, and Guana Island in the Caribbean that feature a unique reptile fauna. This prioritization can be rapidly repeated if new information or techniques become available, and the approach could be replicated elsewhere in the world.

The Biogeography of Globally Threatened Seabirds and Island Conservation Opportunities

A key factor influencing wildlife responses to human activity is the degree to which animals have been previously exposed to human stimuli. On subantarctic Macquarie Island, gentoo penguins Pygoscelis papua breed in areas of high and low human activity (on and off-station, respectively). We investigated the behaviour and breeding success of gentoo penguins on and off-station, by a) comparing the behavioural responses of guarding gentoos before, during and after exposure to standardised pedestrian approaches, and b) employing an observational study to determine how human activity may have contributed to within-season breeding success in light of other environmental and site variables. Behavioural responses to pedestrian visitation by gentoos off-station were significantly stronger than those of birds breeding on-station. However, no relationship was found between pedestrian activity and breeding success off-station. Breeding success was, however, positively related to colony size, and negatively related to the activity of other penguins, the number of nearby southern elephant seal Mirounga leonina harems and the location of colonies within short grassland. On-station, breeding success was amongst the highest recorded for that season. Habituation, predator exclusion and the relevance of these findings for management are discussed.

Reporting costs for invasive vertebrate eradications

Seabirds are the most threatened group of marine animals; 29% of species are at some risk of extinction. Significant threats to seabirds occur on islands where they breed, but in many cases, effective island conservation can mitigate these threats. To guide island-based seabird conservation actions, we identified all islands with extant or extirpated populations of the 98 globally threatened seabird species, as recognized on the International Union for Conservation of Nature Red List, and quantified the presence of threatening invasive species, protected areas, and human populations. We matched these results with island attributes to highlight feasible island conservation opportunities. We identified 1362 threatened breeding seabird populations on 968 islands. On 803 (83%) of these islands, we identified threatening invasive species (20%), incomplete protected area coverage (23%), or both (40%). Most islands with threatened seabirds are amenable to island-wide conservation action because they are small (57% were <1 km(2) ), uninhabited (74%), and occur in high- or middle-income countries (96%). Collectively these attributes make islands with threatened seabirds a rare opportunity for effective conservation at scale.

Importance of lethal control of invasive predators for island conservation

The eradication of invasive species from islands is a conservation intervention proven to protect biodiversity, with more than 1200 successful vertebrate eradications implemented globally. The demand for eradication projects is increasing and practitioners are planning projects on increasingly larger, more remote and more technically challenging islands. Undertaking strategic planning for conservation requires information on both the cost and benefit of proposed actions, to determine the trade-off in selecting one project over another. To date the cost of eradication projects is disparately reported in the literature, an artefact of different reporting requirements based on where the eradication was undertaken, the scale of the project, the implementing agency and its accountabilities, and inconsistency in reporting all project component costs. Eradication projects have characteristics that allow more refined cost forecasting relative to other conservation initiatives, including a narrow set of major eradication techniques being used, a defined beginning and end point, and distinct project components. Here we present the major cost centres for eradication projects, including a dataset for a suite of rodent, ungulate and predator eradications, using a dataset of 46 eradications primarily from New Zealand, Ecuador and the USA. We found cost increased with island size for all eradication types except ground based rodent eradications. Using these standards to report project costs will improve the ability to evaluate and predict the cost of removing invasive animals from islands to protect native insular biodiversity.

Seabird mortality induced by land-based artificial lights

James C. Russell,∗† Holly P. Jones,‡ Doug P. Armstrong,§ Franck Courchamp,∗∗ Peter J. Kappes,†† Philip J. Seddon,‡‡ Steffen Oppel,§§ Mark J. Rauzon,∗∗∗ Phil E. Cowan,††† Gerard Rocamora,† Piero Genovesi,‡‡‡ Elsa Bonnaud,∗∗ Bradford S. Keitt,§§§ Nick D. Holmes,§§§ and Bernie R. Tershy∗∗∗∗ ∗School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand, email j.russell@auckland.ac.nz †Island Biodiversity & Conservation Center, University of Seychelles, P.O. Box 1348, Anse Royale, Republic of Seychelles ‡Department of Biological Sciences and Institute for the Study of the Environment, Northern Illinois University, DeKalb, IL 60115, U.S.A. §Wildlife Ecology Group, Institute of Natural Resources, Massey University, Private Bag 11 222, Palmerston North 4442, New Zealand ∗∗Ecologie Systematique Evolution, Universite Paris-Sud, CNRS, AgroParisTech, Universite Paris-Saclay, 91400 Orsay, France ††Oregon Cooperative Fish and Wildlife Research Unit, Department of Fisheries and Wildlife, Oregon State University, Corvallis, OR 97331, U.S.A. ‡‡Department of Zoology, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand §§RSPB Centre for Conservation Science, Royal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire SG19 2DL, United Kingdom ∗∗∗Geography Department, Laney College, Oakland, CA 94607, U.S.A. †††Landcare Research, P.O. Box 69040, Lincoln 7640, New Zealand ‡‡‡Institute for Environmental Protection and Research, Via V. Brancati 48, Rome I-00144, Italy §§§Island Conservation, 2161 Delaware Avenue Suite A, Santa Cruz, CA 95060, U.S.A. ∗∗∗∗University of California Santa Cruz, 100 Shaffer Road, Santa Cruz, CA 95060, U.S.A.

Past and estimated future impact of invasive alien mammals on insular threatened vertebrate populations

Artificial lights at night cause high mortality of seabirds, one of the most endangered groups of birds globally. Fledglings of burrow-nesting seabirds, and to a lesser extent adults, are attracted to and then grounded (i.e., forced to land) by lights when they fly at night. We reviewed the current state of knowledge of seabird attraction to light to identify information gaps and propose measures to address the problem. Although species in families such as Alcidae and Anatidae can be grounded by artificial light, the most affected seabirds are petrels and shearwaters (Procellariiformes). At least 56 species of Procellariiformes, more than one-third of them (24) threatened, are subject to grounding by lights. Seabirds grounded by lights have been found worldwide, mainly on oceanic islands but also at some continental locations. Petrel breeding grounds confined to formerly uninhabited islands are particularly at risk from light pollution due to tourism and urban sprawl. Where it is impractical to ban external lights, rescue programs of grounded birds offer the most immediate and employed mitigation to reduce the rate of light-induced mortality and save thousands of birds every year. These programs also provide useful information for seabird management. However, these data are typically fragmentary, biased, and uncertain and can lead to inaccurate impact estimates and poor understanding of the phenomenon of seabird attraction to lights. We believe the most urgently needed actions to mitigate and understand light-induced mortality of seabirds are estimation of mortality and effects on populations; determination of threshold light levels and safe distances from light sources; documentation of the fate of rescued birds; improvement of rescue campaigns, particularly in terms of increasing recovery rates and level of care; and research on seabird-friendly lights to reduce attraction.

Literature Review and Meta-Analysis of Vegetation Responses to Goat and European Rabbit Eradications on Islands

Invasive mammals on islands pose severe, ongoing threats to global biodiversity. However, the severity of threats from different mammals, and the role of interacting biotic and abiotic factors in driving extinctions, remain poorly understood at a global scale. Here we model global extirpation patterns for island populations of threatened and extinct vertebrates. Extirpations are driven by interacting factors including invasive rats, cats, pigs, mustelids and mongooses, native species taxonomic class and volancy, island size, precipitation and human presence. We show that controlling or eradicating the relevant invasive mammals could prevent 41–75% of predicted future extirpations. The magnitude of benefits varies across species and environments; for example, managing invasive mammals on small, dry islands could halve the extirpation risk for highly threatened birds and mammals, while doing so on large, wet islands may have little benefit. Our results provide quantitative estimates of conservation benefits and, when combined with costs in a return-on-investment framework, can guide efficient conservation strategies.