Coral reefs in danger of dying out in next 20 years!

The delicate eco-systems, known as the "rainforests of the sea", support huge amounts of marine life. But as oceans absorb carbon dioxide, they become more acidic, making it impossible for coral reefs like the Great Barrier Reef in Australia to survive. Reefs are also at greater danger of bleaching as sea temperatures warm.

Sir David Attenborough, who co-chaired the meeting, said that 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 carbon dioxide in the air. At present, the concentration of carbon dioxide in the atmosphere is 387 parts per million (ppm).

According to Alex Rogers, the scientific director of the International Programme on the State of the Oceans, the figure will reach 450 ppm in the next 20 years if the world continues to burn fossil fuels at the current rate. Once that figure is reached, the ocean will become too acidic for corals 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. That is where corals are now," 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 carbon dioxide, it mixes with the seawater to make carbonic acid, upsetting their and reducing aragonite levels needed by corals.

Mr Rogers said that once carbon dioxide levels in the atmosphere reach the 600 ppm mark, other organisms like plankton and sea snails will start to die and whole marine ecosystems could collapse.

"Five hundred million people are dependent on coral reefs for livelihoods, food and culture," he added. "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 is calling for world leaders to agree 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. "Because if we carry on business as usual collapse is inevitable whereas if we decide to do something about it we can make a difference to the current trajectory."

By Louise Gray, Environment Correspondent, telegraph.co.uk 

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