Coral reefs will all die within 50 years, study finds

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Coral reefs could be wiped from the face of the Earth within the next 50 years, according to one of the most pessimistic assessments yet of the health of the planet's marine life.

Extensive "bleaching", caused by rising ocean temperatures, is leading to an inevitable and irreversible decline of the great coral reef barriers of the tropics, from the Indian Ocean to the Caribbean and covering the entire Pacific Ocean.

Rupert Ormond, a coral specialist from the Marine Biological Station, which is run by the Universities of Glasgow and London, at Millport on the Scottish island of Great Cumbrae, said the bleaching, which began in earnest about four years ago, is getting much worse.

"The picture is that this whitening and then death of corals began to be noticed in a few areas during the 1980s. I became involved in 1997 and 1998 when there was extremely widespread coral bleaching around all the oceans of the world in the tropics and, for the first time, extremely extensive coral bleaching in the Indian Ocean," Dr Ormond told the British Association meeting in Glasgow "Over 60 countries have had massive coral bleaching and mortality extending over large areas. The evidence draws an overwhelming picture that this bleaching is due to steady but almost inevitable rise in ocean temperatures," he said.

As sea temperatures increase, the microscopic plants – on which the tiny coral animals depend – die and the delicate balance between the two organisms is upset, eventually causing the coral to lose its vivid coloration and die.

Dr Ormond said: "This rise in tropical ocean temperatures is now at between about 1C to 2C per hundred years on average and outputs from a whole range of global climate models that have been presented lead one in little doubt that we can explain past bleaching events on the basis of slow climate change and increase in oceanographic temperatures."

That also explained why bleaching was initially observed in the years of El Niño, when warm Pacific Ocean currents change direction, causing more generalised warming in other regions of the world. "But what the computer models are now saying is that, within 10 to 20 years, we'll get massive bleaching on a large scale almost every year and one can predict that maybe within 50 years there will be very little left of corals in coral-reef countries by that period of time," Dr Ormond said.

"Frankly, I find the whole prognosis extremely gloomy. I cannot see what can be done about it given that there is something like a 50-year time-lag between us trying to control carbon dioxide emissions and the temperature of the oceans actually beginning to alter.

"As anyone who has dived on a coral reef knows, it is a spectacular environment. It's been compared to skiing with wildlife thrown in.

"I find it very hard to avoid the conclusion that it is inevitable that most coral in almost all coral-reef areas will be lost in 30 to 50 years. This is the conclusion of quite a number of coral reef biologists who compared climate change with the temperature-sensitivity of corals. Maybe levels weren't close to those upper limits to begin with but they are certainly very close to them now."