CO2 killing our coral reefs, say experts

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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.

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.

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