Globally, corals reefs are being degraded by a number of factors including overfishing, sedimentation and rising ocean temperatures due to greenhouse gas emissions, Selig said.
A rise of just 1 degree to 2 degrees Fahrenheit (about 0.5 degrees to 1 degree Centigrade) above normal summertime highs can kill coral polyps, which build reefs.
Given the difficulty of slowing or reversing the rate of greenhouse gas emissions, coral reef scientists, managers and conservationists had pinned their hopes on a different, more localized strategy: saving corals by restricting fishing in marine protected areas. The reasoning is that fishing depletes herbivorous fishes, which can lead to more seaweed on the seafloor; that can harm baby corals, so restricting the taking of fish that trim back seaweed should help coral populations recover.
Previous research has shown that under optimal conditions, reefs in marine protected areas saw increases in coral cover of 1 percent or 2 percent per year.
But those gains might not be enough to mitigate the impact of thermal stress events. For example, the new study found that when water temperatures were more than 1 degree Centigrade above summertime averages for eight weeks (recognized as the threshold that generally results in widespread bleaching and significant coral death), it correlated with coral cover loss of 3.9 percent annually.
"Reducing overfishing, although clearly a very good thing, will not meaningfully limit the damage being done to the world's coral reefs by greenhouse gas emissions," Bruno added.
Richard B. Aronson, Ph.D., professor and head of the biological sciences department at the Florida Institute of Technology, said the study clearly showed that marine protected areas cannot by themselves save coral reefs.
"We have to reverse climate change by stopping runaway greenhouse gas emissions," said Aronson, who did not participate in the study. "That is a lot h
|Contact: Patric Lane|
University of North Carolina at Chapel Hill