Too late to save reefs, says study

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It is already too late to save most of the world's coral reefs from ocean acidification, warns a recent study.

The research by chemical oceanographers Long Cao and Ken Caldeira studied computer simulations of ocean chemistry at different atmospheric levels of carbon dioxide, ranging from 280 parts per million (pre-industrial levels) to 2000 ppm .

The authors found that many of the world's coral reefs would be devastated even if carbon dioxide levels stabilize at 450 ppm, a level well below many climate change forecasts.

According to Cao, ...even if atmospheric CO2 stabilizes at the current level of 380 ppm, fewer than half of existing coral reef will remain in such an environment. If the levels stabilize at 450 ppm, fewer than 10% of reefs would be in waters with the kind of chemistry that has sustained coral reefs in the past.

If current trends in CO2 emissions continue unabated in the next few decades, we will produce chemical conditions in the oceans that have not been seen for tens of millions of years. We are doing something very profound to our oceans. Ecosystems like coral reefs that have been around for many millions of years just won't be able to cope with the change. adds Caldeira.

This study was initiated as a result of Caldeira's testimony before a subcommittee on Fisheries, Wildlife and Oceans of the US Congress in April 2007.

When asked what stabilization level would be needed to preserve the marine environment, he answered that no such study had yet addressed that question. Cao and Caldeira's study, to be published in the journal Geophysical Research Letters, addresses the gap.

For more information, see the paper Cao, L, and K Caldeira (2008) Atmospheric CO2 stabilization and ocean acidification. Geophysical Research Letters, doi:10.1029/2008GL035072.