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CO2 killing our coral reefs, say experts

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London - The world's coral reefs are in danger of dying out in the next 20 years unless carbon emissions are cut drastically, warns a coalition of scientists led by Sir David Attenborough.

The delicate ecosystems, known as the “rainforests of the sea'', support huge amounts of marine life. But as oceans absorb CO2 they become more acidic, making it impossible for structures such as the Great Barrier Reef in Australia to survive.

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Many coral reefs, often described as the tropical rainforests of the oceans because of their rich diversity of life, could be threatened with extinction by mid-century.

Reefs are also at greater danger of bleaching as sea temperatures warm. Scientists gathered at the Royal Society in London to call for tougher target cuts in emissions. Sir David, who co-chaired the meeting, said the collapse of coral reefs meant the death of marine ecosystems. “We must do all that is necessary to protect the key components of the life of our planet as the consequences of decisions made now will likely be forever as far as humanity is concerned,'' he said. Open water absorbs around a third of the CO2 in the air. At present, the concentration of CO2 in the atmosphere is 387 parts per million (ppm).

Alex Rogers, the scientific director of the International Programme on the State of the Oceans, says the figure will reach 450ppm in the next 20 years if the world continues to burn fossil fuels at the present rate, and once that figure was reached the ocean would become too acidic for coral to survive. “The kitchen is on fire and it's spreading round the house. If we act quickly and decisively we may be able to put it out before the damage becomes irreversible,'' he said.

Coral reefs are living organisms that rely on calcium minerals, called aragonite, in the water to build and maintain their external skeletons. But when the oceans absorb CO2, it mixes with the seawater to make carbonic acid, reducing the aragonite levels. Mr Rogers said that once CO2 levels in the atmosphere reached the 600ppm mark, other organisms - such as plankton and sea snails - would start to die and whole marine ecosystems could collapse.

“Five hundred million people depend on coral reefs for livelihoods, food and culture,'' he said. “The economic implications of the loss of coral reefs are absolutely huge.'' Alongside other scientists from the Royal Society and Zoological Society of London, Mr Rogers wants world leaders to agree to much tougher targets to cut emissions as part of any climate change deal decided in Copenhagen at the end of this year.

“Essentially, coral reefs are on death row and Copenhagen is one of the last opportunities for a reprieve,'' he said. “If we carry on business as usual collapse is inevitable.'' - The New Zealand Herald

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