The West Indies’ coral reefs will disappear in a few decades. This is the shocking result of a new scientific study. Individual coral colonies will survive in the region even in the future, but the coral reef ecosystem as we currently know it will disappear. All this will lead to significant economic losses, particularly for island and coastal people whose livelihoods are closely linked to coral reefs and the ecosystem services they provide.
Global climate change is the main reason for the dramatic changes. The powerful adverse effects were shown in the Eastern Caribbean already in 2005, when the health of the region’s reefs weakened and live cover dropped during an extensive coral bleaching.
The study by Buddemeier et al. tells that it is already too late to stop the reef death. The big changes in the coral reef environment will take place even if substantial emission cuts of greenhouse gases are implemented in the coming years.
The study published in the journal Climate Change in 2011 focuses on Eastern Caribbean reef health and especially the Virgin Islands’ area. The COMBO (COral Mortality and Bleaching Output) model was used for the predictions. Three realistic emission scenarios for greenhouse gases were the basis for the simulation.
The results indicate that future bleaching episodes will be followed by the reduction of live coral cover on the reefs. (Most of the damage will be caused by the warming of sea waters and related bleaching. The decline in reef condition will take place even if the adverse effect of ocean acidification is calculated as minor.)
If there is no adaptation by the corals to the elevated mean water temperatures, the live coral cover on the West Indies’ reefs will decrease to less than 5% already by the year 2035. In a scenario where corals develop an additional 1–1.5 degrees Celcius of heat tolerance (through a shift in the symbiotic algae that live in the coral tissues) coral cover above 5% could last until 2065.
The researchers did not include reefs which are located more than 30m underwater. Live coral cover between 5 and 10% was considered a limit where the reef would not be able to regenerate itself and could not be called a real coral reef any more. For several of these modeling scenarios, the researchers used starting levels of coral cover of 7%, 15%, and/or 30%. These values are realistic values in the Eastern Caribbean.
Buddemeier et al. summarise their study by saying that “coral reef communities are likely to be essentially gone from substantial parts of the Southeast Caribbean by the year 2035, given the current low cover values following the 2005 event” and that “the conversion of coral reefs to fundamentally different systems will have large implications for the provision of ecosystem services”. The authors add: “Given the modeling results presented here, urgent efforts are needed to identify and protect what appear to be the most resilient coral reefs in the Caribbean.”
The whole study (R. W. Buddemeier, Diana R. Lane and J. A. Martinich, Modeling regional coral reef responses to global warming and changes in ocean chemistry: Caribbean case study, Climatic Change, 2011, DOI: 10.1007/s10584-011-0022-z) can be found here: Study by Buddemeier et al.