Global warming may have permanently damaged reefs

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The effects of global warming upon coral reefs have been more devastating than previously believed, according to the first report to show the long-term impact of rising temperatures on fish and invertebrate life.

According to a 50,000 square metre study of 21 sites on the inner islands of the Seychelles undertaken in 1994 and 2005, large areas of coral reef and the organisms that live there, may have been permanently lost due to global warming.

The study, which was undertaken by an international team of biologists, is the first to show the long-term effects of the 1998 heatwave which caused sea temperatures in the Indian Ocean to rise so high that they killed more than 90% of the corals in the inner Seychelles.

Collapsing reefsTheir paper in the Proceedings of the National Academy of Sciences says that while the 90% loss of coral cover was dramatic enough in itself, the long-term prospects are more bleak and many reefs have been unable to recover and many have collapsed into piles of algae-covered rubble.

The study says that the collapse of reefs, which are in part held together by corals, has led to a drop in the amount of food available and shelter from predators, which has had a knock-on effect to the other reef organisms.

The effects of global warming have not just been damaging corals, either. Four fish species, including two labrid wrasses, a Butterflyfish and a damsel are already believed to be extinct in the area, while others have dropped to critically low levels.

Lead author, Nick Graham of Newcastle University's School of Marine Science and Technology said: "Reefs can sometimes recover after disturbances, but we have shown that after severe bleaching events, collapse in the physical structure of the reef results in profound impacts on other organisms in the ecosystem and greatly impedes the likelihood of recovery.

"Unfortunately it may be too late to save many of these reefs but this research shows the importance of countries tackling greenhouse gas emissions and trying to reduce global warming and its effect on some of the world's finest and most diverse wildlife."