Caribbean coral reefs may all be dead by end of the century

A leading science journal says that Caribbean coral reefs could be among the first casualties of increasingly acidic oceans.

The journal, Science, said in its December issue that a recent study has found that carbon emissions from the burning of fossil fuels by humans may pose this problem in less than a half century.
It said that unless carbon dioxide emissions fall in the near future, existing reefs could all be dying by 2100.

“We need rapid reductions in carbon dioxide levels,” said Ove Hoegh-Guldberg, a marine science professor at Australia’s University of Queensland, a lead author of the study.

“The impact of climate change on coral reefs is much closer than we appreciated,” he said, identifying Australia’s Great Barrier Reef, the world’s largest coral expanse, among coral reefs that also could be seriously affected.

“It’s just around the corner,” he said, noting that emissions of carbon dioxide, the main “greenhouse” gas contributing to global warming, were boosting acidity so much that sea water covering 98 per cent of all coral reefs may be too acidic by 2050 for some corals to survive.

Hoegh-Guldberg said while others may survive, they would be unable to build reefs.

“Unless we take action soon, there is a real possibility that coral reefs, and everything that depends on them, will not survive this century,” said Chemical oceanographer Ken Caldeira, another of the study’s researchers.

“About a third of the carbon dioxide put into the atmosphere is absorbed by the oceans which helps slow greenhouse warming, but is a major pollutant of the oceans.”

Caldeira said the absorbed CO2 produces carbonic acid, the same acid that gives soft drinks their fizz, making certain minerals called carbonate minerals dissolve more readily in seawater.

He said this is especially true for aragonite, the mineral used by corals and many other marine organisms, to grow their skeletons.

The researchers said coral reefs, delicate undersea structures resembling rocky gardens that are made by tiny animals called coral polyps, “are important nurseries and shelters for fish and other sea life”.

The Nature Conservancy environmental group said reefs were a very important source of food for millions of people and play a significant role in tourism from Australia to the Caribbean, producing US$375 billion annually in economic value worldwide.

The researchers said the reefs were also a “storehouse” of potential 21st century medicines for cancer and other diseases.

Hoegh-Guldberg said Australian and Caribbean reefs were at the greatest risk because they already have lower carbonate-ion concentrations and, therefore, would “reach critical levels sooner”.

“We need to think of this as the straw that broke the camel’s back,” said Peter Sale of the United Nations University.

The researchers said impending chemical changes may require emissions cuts even more drastic than those for climate alone.

“These changes come at a time when reefs are already stressed by climate change, over-fishing, and other types of pollution,” Caldeira said.

“So, unless we take action soon, there is a very real possibility that coral reefs and everything that depends on them -will not survive this century,” he warned.

Caribbean Broadcasting Corporation, 17 December 2007. Article.

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