Global Warming Sealing the Fate of Coral Reefs

Destroyed by rising carbon levels, acidity, pollution, algae, bleaching and El Niño, coral reefs require a dramatic change in our carbon policy to have any chance of survival.

An aerial view of the coastline along Hawaii Kai on the Hawaiian Island of Oahu where organic sediment is one of the major threats to the reef. Photograph: Ed Darack/Corbis


Animal, vegetable and mineral, a pristine tropical coral reef is one of the natural wonders of the world. Bathed in clear, warm water and thick with a psychedelic display of fish, sharks, crustaceans and other sea life, the colourful coral ramparts that rise from the sand are known as the rainforests of the oceans. 

And with good reason. Reefs and rainforests have more in common than their beauty and bewildering biodiversity. Both have stood for millions of years, and yet both are poised to disappear.

If you thought you had heard enough bad news on the environment and that the situation could not get any worse, then steel yourself. Coral reefs are doomed. The situation is virtually hopeless. Forget ice caps and rising sea levels: the tropical coral reef looks like it will enter the history books as the first major ecosystem wiped out by our love of cheap energy.

Today, a report from the Australian government agency that looks after the nation's emblematic Great Barrier Reef reported that "the overall outlook for the reef is poor and catastrophic damage to the ecosystem may not be averted". The Great Barrier Reef is in trouble, and it is not the only one.

Within just a few decades, experts are warning, the tropical reefs strung around the middle of our planet like a jewelled corset will reduce to rubble. Giant piles of slime-covered rubbish will litter the sea bed and spell in large distressing letters for the rest of foreseeable time: Humans Were Here.

"The future is horrific," says Charlie Veron, an Australian marine biologist who is widely regarded as the world's foremost expert on coral reefs. "There is no hope of reefs surviving to even mid-century in any form that we now recognise. If, and when, they go, they will take with them about one-third of the world's marine biodiversity. Then there is a domino effect, as reefs fail so will other ecosystems. This is the path of a mass extinction event, when most life, especially tropical marine life, goes extinct."

Alex Rogers, a coral expert with the Zoological Society of London, talks of an "absolute guarantee of their annihilation". And David Obura, another coral heavyweight and head of CORDIO East Africa, a research group in Kenya, is equally pessimistic: "I don't think reefs have much of a chance. And what's happening to reefs is a parable of what is going to happen to everything else."

Human impact has tipped that balance. Loaded with the agricultural nutrients nitrates and phosphates, rivers now spill their polluted waters into the sea. Sediment and sewage cloud the clear waters, while over-fishing plays havoc with the finely tuned community of fish and sharks that kept the reef nibbling down to sustainable levels. All of this is enough to wreck coral without any help from climate change.

Global warming, predictably, has made the situation worse. Secure in their tropical currents, coral reefs have evolved to operate within a fairly narrow temperature range, yet, in the late 1970s and 1980s, coral scientists got an unpleasant demonstration of what happens when the hot tap is left on too long. "The algae go berserk," said Rogers. Scientists think the algae react to the warmer water and increased sunlight by producing toxic oxygen compounds called superoxides, which can damage the coral. The coral respond by ejecting their algal lodgers, leaving the reefs starved of nutrients and deathly white. Such bleaching was first observed on a large scale in the 1980s, and reached massive levels worldwide during the 1997-98 El Niño weather event.

For more information see: http://www.guardian.co.uk/environment/2009/sep/02/coral-catastrophic-future