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 Andre´foue¨t et al. Ce´line Bellard1, James Russell2, Benjamin D. Hoffmann3, Camille Leclerc1, and Franck Courchamp1,4 1
Ecologie, Syste´matique, and Evolution, Centre National de la Recherche Scientifique (CNRS) Unite´ 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, Andre´foue¨t 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. Andre´foue¨t 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 Andre´foue¨t 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 Andre´foue¨t 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 Andre´foue¨t, 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
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 Andre´foue¨t et al. Ce´line Bellard1, James Russell2, Benjamin D. Hoffmann3, Camille Leclerc1, and Franck Courchamp1,4 1
Ecologie, Syste´matique, and Evolution, Centre National de la Recherche Scientifique (CNRS) Unite´ 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, Andre´foue¨t 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. Andre´foue¨t 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 Andre´foue¨t 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 Andre´foue¨t 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 Andre´foue¨t, 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
