Status of Caribbean coral reefs after bleaching and hurricanes in 2005

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Predictions for the Future of the Caribbean100%SRES A1b (to 2100) SRES B1 (to 2200)80%60%40%20%with 1.5°C adaptation0%2000 2050 2100 2150 2200Implications f o r Co r a l Reef He a lt hYearsThis model of the frequency that maximum annual degree heating month (DHM), averagedover the 2005 Caribbean bleaching region, exceeds the upper bleaching threshold of2°C-month. The results are from the GFDL climate models under a ‘business-as-usual’scenario (SRES A1b; 2001-2100) and lower emissions scenario (SRES B1; 2001-2200)in which atmospheric CO 2is stabilized at 560 ppm in the year 2100 scenario. The blackline assumes no adaptation by corals and their symbionts; the blue line assumes 1.5°Cthermal adaptation.“… the Caribbean fits the profile of a vulnerable region: biodiversity is far lower thanin the Indo-Pacific; it has been more vulnerable than the Indo-Pacific during pastclimate fluctuations; it is a relatively enclosed basin with a growing human populationin its drainage area and abundant evidence of anthropogenic effects and terrigenous(e.g. runoff-related) influences; there are no other large-scale reef communities in thetropical Atlantic that can serve as refugia or sources of recolonization; and evidence ofwidely distributed reef stress has already been noted.” (Smith and Buddemeier 1992)Climate change poses an existential threat to the already heavily disturbed coral reefs of thewider Caribbean. The conditions that currently cause coral bleaching events are expectedto occur more frequently (every 2 years) within 20-30 years across much of the Caribbean,especially the northern Caribbean. Thermal adaptation by corals and their symbionts couldspare many Caribbean reefs from catastrophic future bleaching events, by allowing time for theworld to reduce greenhouse gas emissions and change the long-term climate forecast.The final effect of the projected increases in the frequency and severity of thermal stress eventson individual coral reefs across the Caribbean will depend on the hydrodynamics of the reefs,the health of individual ecosystems, the degree of other direct human pressures, the structureof the coral community, and the adaptability of the individual corals. It will also depend onthe response of corals to associated changes in ocean chemistry, hurricane activity and diseasetransmission.133
Status of Caribbean Coral Reefs after Bleaching and Hurricanes in 2005Caribbean coral reefs subjected to the more frequent bleaching events projected for the futureare likely to undergo shifts in community structure. This may already be occurring, with majorlosses of the Acropora coral species since the 1970s. Frequent coral bleaching events, especiallywhen combined with direct human pressures like over-fishing, pollution and sedimentationare expected to keep both coral and fish species richness low and lead to more algal-dominatedecosystems. Aggressive reductions in greenhouse gas emissions and local marine conservationefforts are necessary to avoid the long-term degradation of Caribbean coral reef ecosystems.Au t h o r Co n ta c t sSimon Donner, Department of Geography, University of British Columbia, Vancouver, Canada.simon.donner@gmail.comReferencesDonner SD, Knutson TR, Oppenheimer M (2007). Model-based assessment of the role of humaninducedclimate change in the 2005 Caribbean coral bleaching event. Proceedings of theNational Academy of Sciences, 10.1073/pnas.0610122104Donner SD, Skirving WJ, Little CM, Oppenheimer M, Hoegh-Guldberg O (2005). Globalassessment of coral bleaching and required rates of adaptation under climate change.Global Change Biology, 11:2251-2265.Gill JA, Watkinson AR, McWilliams JP, Cote IM (2006). Opposing forces of aerosol cooling andEl Niño drive coral bleaching on Caribbean reefs, Proceedings of the National Academyof Sciences, 103:18870-18873.Intergovernmental Panel on Climate Change (IPCC) (2007). Climate change 2007: ThePhysical Science Basis. Summary for Policymakers. Contribution of Working Group Ito the Fourth Assessment Report of the Intergovernmental Panel on Climate Change.Available at http://www.ipcc.ch.Smith SV, Buddemeier RW (1992). Global change and coral reef ecosystems. Ann Rev Ecol Syst23:89-118134
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Dedication: This book is dedicated
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Status of Coral Reefs in the Caribb
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3. Hu r r i ca n e s a n d t h e i
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Hurricanes and their Effect on Cora
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Hurricanes and their Effect on Cora
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4. Th e 2005 Bl e a c h i n g Ev e
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The 2005 Bleaching Event: Coral-Lis
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5. Stat u s o f t h e Mesoamerican
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6. Co r a l Reefs o f t h e U.S. Ca
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Coral Reefs of the U.S. Caribbean19
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7. Th e Effects o f Co r a l Bl e a
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The Effects of Coral Bleaching in t
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Status of Caribbean coral reefs after bleaching and hurricanes in 2005

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