Indian Ocean 'heatwaves' Spell Disaster for Coral

Vast areas of coral reef could perish within the next few decades in a procession of cyclic "heatwaves" in the Indian Ocean, a marine biologist warns today.

Charles Sheppard, of Warwick University, reports in the journal Nature that in 1998, unusually high sea temperatures killed more than 90% of the corals on shallow Indian Ocean reefs, and such events in future could finish the job.

"In 1998, there was a huge wipeout of corals," Dr Sheppard said. "The global figure seems to have been about 16% of all corals, but the Indian Ocean was the worst affected."

"I have dived on reefs there for a whole hour, and not seen one left alive."

The El Nino phenomenon in 1998 saw a huge body of warmer water moving across the equatorial Pacific. The corals that died as a result were up to 500 years old. Reefs are among the richest habitats on the planet; it would take centuries for one to recover fully.

Coral might be able to acclimatise to a gradual temperature rise over years, but Dr Sheppard has used historical data and climate models to predict that ocean temperatures are likely to go through a peaking effect similar to that of 1998 approximately every five years.

"For the area 10 to 15 degrees south, by the year 2020 it is going to reach what I call extinction point - which is much closer than a lot of us thought," he said.