Coral reefs threatened by rising CO2 levels: study Coral reefs threatened by rising CO2 levels: study

WASHINGTON (AFP) – The survival of the world’s coral reefs will be seriously threatened by 2050 if atmospheric levels of carbon dioxide (CO2) and the acidity of ocean waters continue to rise at the present rate, said a study published Thursday.

High acidity dissolves minerals in the water that speed up calcification of corals leading to their premature death, warned researchers of the Washington-based Carnegie Institution in their study in Science magazine.

Unless emissions of CO2 — global warming’s main contributor — are stabilized and reduced, 98 percent of coral reef habitats will be immersed in excessively acid waters, said oceanographers and study co-authors Ken Caldeira and Long Cao.

Their estimates are based on computer models of the ocean water’s changing chemical composition with rising CO2 levels in the atmosphere — from pre-industrial 280 parts per million (ppm) to the current 380 ppm, all the way up to 500 ppm.

Carbon dioxide emissions are on the rise chiefly due to human activities, above all from the massive burning of fossil fuels, scientists said.

“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,” said Caldeira.

The absorbed CO2 produces carbonic acid that dissolve certain minerals, especially argonite, which is used by corals to grow their skeletons, he said.

If atmospheric CO2 stabilizes at 550 ppm, said Cao, “no existing coral reef will remain in such an environment.”

According to Bob Steneck of the University of Maine and another co-author of the paper, around one billion people in Asia depend on coral reef fisheries.

“Corals are feeling the effects of our actions and it is now or never if we want to safeguard these marine creatures and the livelihoods that depend on them,” he added.

The authors will also present their study Thursday before the American Geophysical Union, in San Francisco, California.


Agence France Presse, 13 December 2007. Article.


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