Download Climate change, sea-level rise, and conservation: keeping island

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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
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Trends in Ecology & Evolution March 2014, Vol. 29, No. 3
Already exnct
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0%
Facing imminent exncon
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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
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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
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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
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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
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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
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end of trying to recreate past ecological communities. Trends Ecol.
Evol. 26, 216–221
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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
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secondary consequences from human displacement for island
biodiversity. Global Change Biol. 18, 2707–2719
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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
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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
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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
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