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Forum Climate change, sea-level rise, and conservation: keeping island biodiversity afloat Franck Courchamp1, Benjamin D. Hoffmann2, James C. Russell3, Camille Leclerc1, and Céline Bellard1 1 Ecologie, Systématique et Evolution, UMR CNRS 8079, University of Paris Sud, Orsay Cedex 91405, France CSIRO, Ecosystem Sciences, PMB 44, Winnellie, NT 0822, Australia 3 University of Auckland, School of Biological Sciences and Department of Statistics, Private Bag 92019, Auckland 1142, New Zealand 2 Island conservation programs have been spectacularly successful over the past five decades, yet they generally do not account for impacts of climate change. Here, we argue that the full spectrum of climate change, especially sea-level rise and loss of suitable climatic conditions, should be rapidly integrated into island biodiversity research and management. Island conservation in the longer term Conservation of biodiversity on islands is important globally because islands are home to more than 20% of the terrestrial plant and vertebrate species in the world, within less than 5% of the global terrestrial area. Endemism on islands is a magnitude higher than on continents [1]; ten of the 35 biodiversity hotspots in the world are entirely, or largely consist of, islands [2]. Yet this diversity is threatened: over half of all recent extinctions have occurred on islands, which currently harbor over one-third of all terrestrial species facing imminent extinction [3] (Figure 1). In response to the biodiversity crisis, island conservation has been an active field of research and action. Hundreds of invasive species eradications and endangered species translocations have been successfully completed [4–6]. However, despite climate change being an increasing research focus generally, its impacts on island biodiversity are only just beginning to be investigated. For example, invasive species eradications on islands have been prioritized largely by threats to native biodiversity, eradication feasibility, economic cost, and reinvasion potential, but have never considered the threat of sea-level rise. Yet, the probability and extent of island submersion would provide a relevant metric for the longevity of long-term benefits of such eradications. The impact of sea-level rise on islands Recent research suggests that impacts on islands from sealevel rise will be substantial [2,7–9]. Current scenarios for Corresponding author: Courchamp, F. ([email protected]). Keywords: sea-level rise; climate change; climatic niche shift; island conservation; prioritization. 0169-5347/$ – see front matter ß 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.tree.2014.01.001 sea-level rise vary from 0.26 to 2.3 m by 2100, whereas a rise of 2 or 3 m might happen in the following centuries (see [2,10] and references therein). Moreover, greater tidal ranges, in particular centennial tides, will lead to periodic floods that will destroy nonsaline habitats. Increased frequency and amplitude of seawater floods are also expected to be more common with global climate change. Sea-level rise will also increase coastal erosion (e.g., in the range of 50–200 times that of sea-level rise) and saline water intrusion [9]. Furthermore, shoreline retreat will also lead to massive displacement of anthropogenic activities from coasts [9], which will lead to additional habitat loss further inland. Despite clear and imminent risks, the consequences of sea-level rise for island biodiversity remain one of the least studied of all climate-change issues, both locally and globally, which is surprising when one considers both the number of islands concerned (over 180 000 worldwide) and the potential impact. Even with the most optimistic scenario, many low-lying islands will simply be entirely submerged, threatening most of their biodiversity and many benefits from recent conservation actions. A recent analysis focusing on 4500 islands in ten biodiversity hotspots suggested that 6–19% of these islands could be entirely submerged with a 1–6 m sea-level rise, threatening over 300 endemic species with extinction [2]. Given that they represent the largest proportion of the existing islands, most (69%) of the threatened islands are continental. Yet, unsurprisingly, coral atolls, which are believed to comprise almost 15% of all islands, are disproportionately threatened (27%). A similar study in the Pacific and South East Asia predicted that 15–62% of 12 900 islands could be completely inundated [8]. More globally, a recent study of over 1200 islands from all oceans found comparable results, suggesting a possibility of 6–12% of islands worldwide being entirely submerged [7]. This would amount to a total loss of 10 000–20 000 of the 180 000 islands worldwide, with many more suffering partial losses. The change of climates on islands Climatic shift is another issue that is particularly pertinent to island conservation. Following climate change, the area of climatic parameters that is suitable for any given species is expected to change spatially, within this century [11]. These shifts will occur predominantly upward Trends in Ecology & Evolution, March 2014, Vol. 29, No. 3 127 Forum Trends in Ecology & Evolution March 2014, Vol. 29, No. 3 Already exnct 100% 90% 49 121 27 24 8 16 80% 70% 60% 50% 40% 30% 20% 10% 0% Facing imminent exncon 100% 90% 80 128 95 51 89 328 80% 70% 60% 50% 40% 30% 20% 10% 0% TRENDS in Ecology & Evolution Figure 1. Proportion of extinct and threatened species on islands (dark gray) and the mainland (light gray). Numbers are species and represent mammals ( ), birds ( ), and reptiles and amphibians ( ), showing that terrestrial vertebrate biodiversity is generally more threatened on islands. Data from [3]. (in altitude) and poleward (in latitude). On small islands, this shift may project suitable climates hundreds of kilometers beyond island limits. Consequently, small islands are likely to have a complete change of climatic parameters over their entire surface and many species on those islands will potentially face unsuitable climatic conditions. Whereas continental species can avoid extinction by migrating to follow the climate shift, many insular species cannot. Thus, because such species will be unable to disperse from their original island, they would have to adapt rapidly or will become extinct. Where not already done so, climate change should immediately be integrated into research and management programs for island biodiversity. Here, we highlight two approaches for doing just that, which will identify solutions that will help safeguard biodiversity and protect conservation investments against future global climate change. Account for sea-level rise when prioritizing island restoration Over 900 successful eradications of alien invasive vertebrates have been conducted on islands worldwide (http:// eradicationsdb.fos.auckland.ac.nz). In most cases, such as 128 the Surprise Island project, restoration was conducted without a consideration of climate change (Box 1), resulting in some suboptimal choices for long-term conservation benefits. In January 2010, rat eradication led by one of us (J.C.R.) on the 28-ha island of Honuea (in Tetiaroa, an atoll in the Windward group of the Society Islands of French Polynesia) failed because it was completely flooded by tropical cyclone Oli the day after final baiting occurred throughout the island. Increased frequency and amplitude of cyclones following climate change are indeed increasingly likely to flood low-lying islands and interfere with conservation programs. Of 604 islands where invasive vertebrates have been eradicated and for which elevation data are available [2,12], 26 are predicted to be completely inundated with a 1 m increase in sea level, and many more will be impacted by partial habitat loss (Figure 2). Researchers are increasingly developing prioritization frameworks to help guide decision-making on which islands should be targeted for restoration via invasive species removal. Quite simply, the anticipated level of island submersion should become one of the primary factors to consider for restoration prioritization, so that conservation gain is further optimized, and over longer time horizons. To do so, geographic data, such as island area and elevation profile, and a variety of inundation models at local, regional, and global scales [13], will need to be explicitly incorporated into prioritization frameworks. Consequently, islands with greater elevations may become a priority for invasive species eradication, which will require further research to increase the scale of island eradications, because islands with greater elevations are also often larger. Such islands will also suffer complex exposure to climate change. Consider translocations to save island species from climate change For many island species that cannot adapt or migrate to a suitable nearby island, practitioners will eventually be faced with a decision to either let them go extinct by doing nothing or to attempt to save them by actively moving them to suitable habitat. Species translocations have long been a powerful conservation tool, especially for island conservation, but are controversial, because they can also lead to biological invasions. Many translocations were originally to islands, to alleviate impacts of alien invasive species [6]; however, in the future, translocations may have to be from islands to mitigate climate loss [5]. Thus, the assisted migration of threatened species from islands will require a framework that considers not only the probability of success and lack of impacts in the new introduced range [14], but also the more intractable value issues that emerge when deciding how to manage species [15], such as which species to move, when, and to where. Concluding remarks: securing long-term conservation benefits Currently, the removal of invasive species from islands is one of the most powerful tools for preventing extinctions and restoring ecosystems. To safeguard the biodiversity benefits secured through these restoration programs and to maximize future benefits, implications of climate change Forum Trends in Ecology & Evolution March 2014, Vol. 29, No. 3 Box 1. The restoration of Surprise Island In the coming decades, thousands of low-lying coral atolls around the world will be vulnerable to sea-level rise, predominantly due to expansion of ocean water and mass loss of mountains glaciers and ice sheets. Tropical atolls of some island nations are already experiencing inundation. Importantly, sea-level rise is predicted to be heterogeneous: due to spatial heterogeneity of surface temperatures and other complex, interacting sets of factors, sea levels in some oceanic areas will rise more than in others. Thus, the persistence of atoll islands will depend strongly on location, local conditions, and geomorphology. Therefore, on some of these islands, the conservation benefits of important restoration efforts may be lost in the long term. Surprise Island (Figure I), located in the Entrecasteaux reef off New Caledonia, provides one example of island conservation research and action that did not integrate climate change. Only a few meters above sea level, the small and remote island was the focus of a research program that ended in 2009 with the eradication of introduced rats (Rattus rattus), mice (Mus musculus), and an invasive plant (Cassytha filiformis). The eradication of alien invasive species from Surprise Island was a positive conservation action. It has undoubtedly helped protect the local species for the coming decades, possibly preventing some of them from local extinction. In addition, it provided a wealth of knowledge necessary for island conservation that can be applied to other islands. Notably, research investigating species interactions helped mitigate unexpected ecological chain reactions during eradications, which has been observed during other eradication programs. Research and conservation actions were a result of substantial investment in resources, lasting over a decade. Despite careful planning and long-term commitment, it did not occur to those of us involved in this program (F.C.) that expected sea-level rise would threaten the benefits from our conservation actions. Many other alien species eradication programs have taken place on islands that are doomed in the long term by sea-level rise. Of course, most of these eradication efforts occurred before current understanding of climate change and an ability to measure its impacts. Also, on some of these islands, a rapid conservation response was required despite the long-term threat of climate change. Nonetheless, future conservation programs must take the full breadth of climate change into account, by prioritizing islands according to threats from sea-level rise and climate shifts, and by considering translocation of island species that will be lost to climate change. TRENDS in Ecology & Evolution Figure I. Surprise Island (24 ha), 230 km north of New Caledonia. must become a priority for research and conservation agendas. Research should focus on better understanding and predicting the impacts of sea-level rise and climatic shifts at both the organismal and ecosystem levels on islands. Researchers and practitioners should rapidly integrate these effects of climate change into the planning and prioritizations that are currently taking place. They also should begin to assess island species that are most likely to be at risk from future climate change and the options for preventing their extinction. Key: 0% 0–20% 20–40% 40–60% 60–80% 80–100% 100% TRENDS in Ecology & Evolution Figure 2. Predicted area submersion on islands with an invasive vertebrate eradication program. The size and color of points represent the percentage of surface immersion. With a 1-m sea-level rise, 4% (26) of the 604 islands with an eradication program would be entirely under water and many more would lose a large part of their habitat. Islands and their elevations come from the Database of Island Invasive Species Eradications [4], which is combined with the island sea-level rise model from [2]. 129 Forum Acknowledgments We thank Nick Holmes for access to the Island Invasive Species Eradications Database and C. Josh Donlan for discussions and input on the draft manuscript. Two anonymous referees provided helpful feedback on the manuscript. F.C., C.L., and C.B. were supported by the Agence Nationale de la Recherche. B.D.H. and J.C.R. thank the Ecologie, Systématique et Evolution laboratory at the University of Paris Sud for hospitality. J.C.R. was supported by a sabbatical grant-in-aid from the University of Auckland. References 1 Kier, G. et al. (2009) A global assessment of endemism and species richness across island and mainland regions. Proc. Natl. Acad. Sci. U.S.A. 23, 9322–9327 2 Bellard, C. et al. (2013) Impact of sea level rise on the 10 insular biodiversity hotspots. Global Ecol. Biogeogr. 23, 203–212 3 Ricketts, T.H. et al. (2005) Pinpointing and preventing imminent extinctions. Proc. Natl. Acad. Sci. U.S.A. 102, 18497–18501 4 Veitch, C.R. et al. (2011) Island Invasives: Eradication and Management, IUCN 5 Thomas, C.D. (2011) Translocation of species, climate change, and the end of trying to recreate past ecological communities. Trends Ecol. Evol. 26, 216–221 130 Trends in Ecology & Evolution March 2014, Vol. 29, No. 3 6 Armstrong, D.P. and Seddon, P.J. (2008) Directions in reintroduction biology. Trends Ecol. Evol. 23, 20–25 7 Bellard, C. et al. (2013) Impact of sea level rise on the french islands worldwide. Nat. Conserv. 5, 75–86 8 Wetzel, F.T. et al. (2013) Vulnerability of terrestrial island vertebrates to projected sea-level rise. Global Change Biol. 19, 2058–2070 9 Wetzel, F.T. et al. (2012) Future climate change driven sea-level rise: secondary consequences from human displacement for island biodiversity. Global Change Biol. 18, 2707–2719 10 Levermann, A. et al. (2013) The multimillennial sea-level commitment of global warming. Proc. Natl. Acad. Sci. U.S.A. 110, 13745–13750 11 Mora, C. et al. (2013) The projected timing of climate departure from recent variability. Nature 502, 183–187 12 Bellard, C. et al. (2012) Impacts of climate change on the future of biodiversity. Ecol. Lett. 15, 365–377 13 Mcleod, E. et al. (2010) Sea-level rise impact models and environmental conservation: a review of models and their applications. Ocean Coast. Manag. 53, 507–517 14 Rout, T.M. et al. (2013) How to decide whether to move species threatened by climate change. PLoS ONE 8, e75814 15 Redpath, S.M. et al. (2012) Understanding and managing conservation conflicts. Trends Ecol. Evol. 28, 100–109 Letters Conservation of low-islands: high priority despite sea-level rise. A comment on Courchamp et al. Serge Andréfouët1, Jérome Aucan2, Hervé Jourdan3, Paul Kench4, Christophe Menkes5, Eric Vidal3, and Hiroya Yamano6 1 Institut de Recherche pour le Développement (IRD), Unité de Recherche 227 CoRéUs, LABEX CORAIL, BP A5, 98848 Nouméa, New Caledonia 2 Institut de Recherche pour le Développement, Laboratoire d’Etudes en Géophysique et Océanographie Spatiale (LEGOS), BP A5, 98848 Nouméa, New Caledonia 3 Institut Méditerranéen de Biodiversité et d’Écologie Marine et Continentale (IMBE), Aix-Marseille Université, Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD), Université d’Avignon et des Pays de Vaucluse (UAPV), Centre IRD Nouméa, BP A5, 98848 Nouméa, New Caledonia 4 School of Environment, The University of Auckland, New Zealand 5 Institut de Recherche pour le Développement, Sorbonne Universités (Université Pierre et Marie Curie; Université Paris 06)– CNRS–Muséum National d’Histoire Naturelle–Institut Pierre Simon Laplace, LOCEAN Laboratory, IRD Nouméa, BP A5, 98848 Nouméa, New Caledonia 6 National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan No triage conservation strategy for low tropical islands! Assuming that a simple drowning model is applicable to all islands facing future climate change and sea-level rise (SLR), the future existence of up to 12% of islands is said to be compromised – and therefore these should not be considered for active management and protection [1,2]. This includes tropical atolls and their low-lying islands. However, we reject the triage strategy elaborated by Courchamp et al. [1]. Evidence from geology, sedimentology, and oceanography, and from the ecology of invasive species, shows that island conservation, especially of low islands, should remain a priority. Geological, sedimentary, relative SLR, and tectonic evidence Simplistic drowning models over-state the risks and are inappropriate for low-lying coral reef islands. Such modeling assumes that islands are passive geological entities that will experience permanent inundation with SLR and are unable to physically respond. This is only likely for hard rock coasts, whereas sedimentary shorelines, including coral reef islands which are composed of sand and gravel, display a diverse range of physical responses. During the mid-Holocene (6000–2000 years ago), morphostratigraphy and radiometric dating show that reef islands formed under rising, falling, and stable sea levels. Islands in the Maldives and Marshall Islands formed under rising sea levels (0.5–1.0 m higher than present) [3,4], whereas some Great Barrier Reef and New Caledonian reef islands formed at stable higher sea levels [5]. In these regions sea levels subsequently fell to current levels 2000 years ago. Over the next century the sea level will simply reoccupy the levels under which the islands formed. Corresponding author: Andréfouët, S. ([email protected]) 0169-5347/ ß 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.tree.2014.10.001 At decadal timescales, instead of simply eroding or shrinking, islands can display a complicated spectrum of geomorphic responses. Over the past half-century, under a SLR of 2.0 mm/year, reef islands in the Tuvalu and Marshall Islands have remained stable in size or have become larger [6]. Islands are dynamic landforms that can adjust their shape and position on reefs and build vertically. Physical island change is mediated by the supply and transport of coral sediment rather than by sea level [4]. As waves and currents change, island sediments are reworked alongshore, around shorelines, or onto island surfaces via overwash processes allowing island surfaces to aggrade. In the Maldives, large sections of islands have vertically accreted by 0.3 m over the past decade, a rate much larger than anticipated sea-level rise. At centennial timescales, the 5th IPCC (Intergovernmental Panel on Climate Change) reports that the rate of global mean SLR during the 21st century will exceed the 1971–2010 rate for all representative concentration pathway (RCP) scenarios [7]. However, SLR will also exhibit strong regional variations from the mean trend. Thus, a simple drowning model with a globally uniform sea level would be inappropriate for taking conservation decisions. Major uncertainty in centennial projections lies in decadal variations, which can differ by more than 100% from the global long-term projected change [7]. For instance, during the past 20 years the Solomon Islands and Micronesia have experienced SLR rates above 10 mm.y1. Conversely, New Caledonia has experienced rates lower than 1 mm.y1 over the past 50 years, and conclusions about future impacts are very uncertain. Stating that conservation efforts in Surprise Island (New Caledonia) are doomed therefore seems to be inappropriate [1]. Tectonic processes can also cause vertical land movements that have a predominant role compared to SLR [8]. For instance, in the Torres Islands (Vanuatu) the drowning rate can be much higher than that caused by Trends in Ecology & Evolution, January 2015, Vol. 30, No. 1 1 Letters SLR. Conversely, uplift (e.g., following earthquakes, as occurred recently in the Futuna, Vanuatu, and Solomon Islands) can offset SLR. Conservation strategy and invasive species Low-lying islands, including coral atolls, contain irreplaceable features without any equivalent on high islands. For instance, many seabirds nest on low islands where they are impacted by introduced animals [9], with onethird of seabird species now being considered to be at risk of extinction. In many cases, control or eradication of aliens in these islands promoted rapid recolonization by seabirds. Abandoning such initiatives would impact negatively upon these populations. Invasive species are one of the primary extinction drivers on islands. Certainly, eradication programs on islands expected to drown shortly would be a waste of effort. However, we contend that the number of entirely drowned islands has been grossly overestimated. Partially flooded islands will need better management because the impact of exotic species is likely to become stronger with shrinking, fragmented habitats [10]. Finally, species translocation was proposed to mitigate SLR effects [1]. Translocation can represent a last-chance strategy, but this should not be seen as an innocuous tool. It can produce unpredictable ecosystem changes on receiving islands [11]. Instead, low-lying islands should be prioritized in restoration programs through invasive species eradication, especially when critically endangered and endemic populations are still remnant. To conclude, low-lying islands are at the forefront of the consequences of global change but responses to SLR will be highly variable. A simple and globally uniform approach Trends in Ecology & Evolution January 2015, Vol. 30, No. 1 to drowning will yield errant results, and is an inappropriate basis upon which to prioritize conservation efforts. Conservationists cannot be passive about low-lying islands. They represent irreplaceable sentinels to observe the interplays between climate change and biological invasions, and to experiment the best strategies and means to mitigate their effects. References 1 Courchamp, F. et al. (2014) Climate change, sea-level rise, and conservation: keeping island biodiversity afloat. Trends Ecol. Evol. 29, 127–130 2 Bellard, C. et al. (2014) Impact of sea level rise on the 10 insular biodiversity hotspots. Global Ecol. Biogeogr. 23, 203–212 3 Kench, P.S. et al. (2005) New model of reef-island evolution: Maldives, Indian Ocean. Geology 33, 145–148 4 Kench, P.S. et al. (2014) Evidence for coral island formation during rising sea level in the Central Pacific Ocean. Geophys. Res. Lett. 41, 820–827 5 Yamano, H. et al. (2014) Late Holocene sea-level change and reef-island evolution in New Caledonia. Geomorphology 222, 39–45 6 Ford, M.R. and Kench, P.S. (2014) Formation and adjustment of typhoon-impacted reef islands interpreted from remote imagery: Nadikdik Atoll, Marshall Islands. Geomorphology 214, 216–222 7 Church, J.A. et al. (2013) Sea level change. In Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (Stocker, T.F. et al., eds), pp. 1137–1216, Cambridge University Press 8 Ballu, V. et al. (2011) Comparing the role of absolute sea-level rise and vertical tectonic motions in coastal flooding, Torres Islands (Vanuatu). Proc. Natl. Acad. Sci. U.S.A. 108, 13019–13022 9 Spatz, D.R. et al. (2014) The biogeography of globally threatened seabirds and island conservation opportunities. Conserv. Biol. 28, 1282–1290 10 Blackburn, T.M. et al. (2004) Avian extinction and mammalian introductions on Oceanic islands. Science 305, 1955–1958 11 Ricciardi, A. and Simberloff, D. (2009) Assisted colonization is not a viable conservation strategy. Trends Ecol. Evol. 24, 248–253 Adapting island conservation to climate change. Response to Andréfouët et al. Céline Bellard1, James Russell2, Benjamin D. Hoffmann3, Camille Leclerc1, and Franck Courchamp1,4 1 Ecologie, Systématique, and Evolution, Centre National de la Recherche Scientifique (CNRS) Unité Mixte de Recherche 8079, University of Paris Sud, Orsay CEDEX 91405, France 2 University of Auckland, School of Biological Sciences and Department of Statistics, Private Bag 92019, Auckland 1142, New Zealand 3 Commonwealth Scientific and Industrial Research Organisation (CSIRO), Ecosystem Sciences, PMB 44, Winnellie, Northern Territory 0822, Australia 4 Department of Ecology and Evolutionary Biology and Center for Tropical Research, Institute of the Environment and Sustainability, University of California Los Angeles, CA 90095, USA In a recent Forum article [1] we argued that conservation on islands should better incorporate climate change in Corresponding author: Bellard, C. ([email protected]) 0169-5347/ ß 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.tree.2014.11.003 2 management prioritization schemes. Most species at risk of extinction are threatened by multiple factors [2] including habitat loss, biological invasions, pollution, overexploitation, and climate change. In particular, biological invasions are currently the greatest cause of insular biodiversity decline [3], but climate change and sea-level rise are likely to become more significant threats in the Letters future [4]. We argued that most conservation programs or prioritization schemes are still implemented focusing on one threat only (e.g., [5]), but several threats will almost always occur simultaneously, and sometimes synergistically [6]. We also proposed that island conservation prioritization exercises must include geographic data, such as island area and elevation profile, and a variety of sea-level rise inundation models at local, regional, and global scales. Our goal was to help effect better prioritization of management actions and durably maximize conservation outcomes. In response, Andréfouët et al. [7] supported our call for better prioritization of island conservation, with particular emphasis on the eradication of invasive species from low-lying islands. Andréfouët et al. [7], however, understood our call as one for a ‘triage conservation strategy’, meaning that we suggest abandoning low tropical islands. Importantly, we by no means suggest this, but make the point that continuing ‘business as usual’ is not an option if limited conservation resources are to be efficiently allocated to effectively prevent biodiversity loss. Investing resources on invasive alien species removal programs makes most sense on islands where biodiversity will persist, unless eradication is an interim step before translocation. If not, such efforts will be annulled, resulting in both a loss of investment and credibility in the eyes of funders and the public. Such losses are even less acceptable when the outcome was predictable and alternative islands were available where pest removal would have had a longer-lasting effect. The claim by Andréfouët et al. [7] that ‘low-lying islands should be prioritized in restoration programs through invasive species eradication’ perpetuates the risk of focusing on prioritization by single threats, and optimizes biodiversity only in the short term. Such overly simplistic management needs to be reconsidered, especially when sophisticated algorithms are now available for conservation prioritization incorporating multiple threats, values, and uncertainties [8]. Adapted prioritization schemes can account for the uncertainty associated with estimates of climate change, sea-level rise, or even physical responses of islands, if any. Terrestrial continental conservation programs are already well advanced in incorporating multiple threats to biodiversity management (e.g., [9,10]) and it behoves island conservation to follow suit. Conservation efforts would not prioritize invasive species management in a continental area that was about to be clear-felled; why would it be more sensible to conduct an eradication on a Trends in Ecology & Evolution January 2015, Vol. 30, No. 1 low island if there is a high risk that the island will be permanently inundated in the near future? In addition, we proposed translocation to protect species in response to climate change. Rather than a ‘last-chance strategy’, as suggested by Andréfouët et al. [7], we see translocation as a powerful, and under-utilized, conservation tool to return species throughout their former range, including on both high and low islands, such as has been implemented so successfully in New Zealand [11]. This is certainly a topic on which research and discussion should and will continue; regardless, as often in conservation biology, the need for difficult management decisions will remain. Ultimately, island conservationists need to strike a balance as to whether it is strategically better to prioritize conservation efforts based only on current threats, or also to account for future threats such as climate change. We suggest that the latter maximizes the time-horizon for island conservation, and we reiterate our call for relevant prioritizations incorporating multiple current and future threats and all levels of uncertainty, as has been done in other systems (e.g., [9]), to better prioritize, protect, and restore island ecosystems. References 1 Courchamp, F. et al. (2014) Climate change, sea-level rise, and conservation: keeping island biodiversity afloat. Trends Ecol. Evol. 29, 127–130 2 Tingley, M.W. et al. (2013) Climate change must not blow conservation off course. Nature 500, 271–272 3 Simberloff, D. et al. (2013) Impacts of biological invasions: what’s what and the way forward. Trends Ecol. Evol. 28, 58–66 4 Bellard, C. et al. (2012) Impacts of climate change on the future of biodiversity. Ecol. Lett. 15, 365–377 5 Dawson, J. et al. (2014) Prioritizing islands for the eradication of invasive vertebrates in the United Kingdom Overseas Territories. Conserv. Biol. 00, 1–11 6 Sala, O.E. et al. (2000) Global biodiversity scenarios for the year 2100. Science 287, 1770–1774 7 Andréfouët, S. et al. (2015) Conservation of low-islands: high priority despite sea-level rise. A comment on Courchamp et al. Trends Ecol. Evol. 30, 1–2 8 Bottrill, M.C. et al. (2008) Is conservation triage just smart decision making? Trends Ecol. Evol. 23, 649–654 9 Evans, M.C. et al. (2011) What to do in the face of multiple threats? Incorporating dependencies within a return on investment framework for conservation. Divers. Distrib. 17, 437–450 10 Burgess, N. et al. (2006) Factoring species, non-species values and threats into biodiversity prioritisation across the ecoregions of Africa and its islands. Biol. Conserv. 127, 383–401 11 Armstrong, D.P. and Seddon, P.J. (2008) Directions in reintroduction biology. Trends Ecol. Evol. 23, 20–25 3