CO2 curbs may be too late for reefs, study warns

David Adam, environment correspondent
The Guardian,
Monday October 27 2008

Plight of the coral reefs. Photograph: Sterling Zumbrunn/CI
A new global deal on climate change will come too late to save most of the world's coral reefs, according to a US study that suggests major ecological damage to the oceans is now inevitable.
Emissions of carbon dioxide are making seawater so acidic that reefs including the Great Barrier Reef off Australia could begin to break up within a few decades, research by the Carnegie Institution at Stanford University in California suggests. Even ambitious targets to stabilise greenhouse gas levels in the atmosphere, as championed by Britain and Europe to stave off dangerous climate change, still place more than 90% of coral reefs in jeopardy.
Oceanographers Long Cao and Ken Caldeira looked at how carbon dioxide dissolves in the sea as human emissions increase. About a third of carbon pollution is soaked up in this way, where it reacts with seawater to form carbonic acid. Experts say human activity over the last two centuries has produced enough acid to lower the average pH of global ocean surface waters by about 0.1 units.
Such acidification spells problems for coral reefs, which rely on calcium minerals called aragonite to build and maintain their exoskeletons.
"We can't say for sure that [the reefs] will disappear but ... the likelihood they will be able to persist is pretty small," said Caldeira.
The new study was prompted by questions by a US congressional committee on how possible carbon stabilisation targets would affect coral loss.