Exposed reefs growing again off Sumatra

One of the greatest mass deaths of coral ever recorded occurred when islands were lifted more than a metre out of the water in the 8.7-magnitude earthquake of March 2005 off the west coast of Indonesia’s Sumatra island, scientists said on Thursday.

The earthquake, which was linked to the December 26 2004 tremblor that triggered the massive Indian Ocean tsunami, uplifted Simeulue and Banyak by 1.2m, exposing up to 40,000 sq km of reefs, the report says.

However, new reefs off Simeulue and Banyak islands had started to grow despite conditions being very different from before the quake that killed 638 people, the researchers from the Wildlife Conservation Society (WCS) and the Australian Research Council Centre of Excellence for Coral Reef Studies (ARCCoERS) found.

This demonstrates how coral is able to adapt relatively rapidly to changing circumstances, the report concludes.

“This is a unique opportunity to document a process that occurs maybe once a century and promises to provide new insights into coral recovery processes that until now we could only explore on fossil reefs,” said Dr Andrew Baird of ARCCoERS.

The Global Coral Reef Monitoring Project, an alliance of international organisations, estimated that 16 per cent of the world’s reefs, from the Great Barrier Reef in Australia to the Maldives, were blighted by bleaching during the 1998 El Niño. But this occurred over months and 40 per cent is thought to have recovered completely. The Simeulue and Banyak mortality, however, was virtually instantaneous and irreversible, said Stuart Campbell of WCS.

“What happened on Simeulue and Banyak is a story of mass mortality on a scale rarely observed,” he said. “In contrast to other threats like coral bleaching, none of the corals uplifted by the earthquake have survived.”

Some reefs in the Solomon Islands suffered a similar fate during an earthquake last week but on a much smaller scale.

Peter Mous, a senior scientist with The Nature Conservancy in Indonesia, said over the past decade scientists had become increasingly aware of coral’s ability to recover after a disaster. “There can be many reasons why a particular coral was not found at a specific depth before, for example,” he said. “This is a reshuffling of the cards, so to speak.”

Dr Campbell predicted it would take up to 20 years for the Simeulue and Banyak reefs to grow back to their previous state, provided they were not hit by bleaching, overfishing, bombing, development or other threats.

In 2002 the World Resources Institute estimated that 86 per cent of Indonesia’s reefs were at medium, high or very high threat of destruction. Experts say while awareness of the importance of coral reef conservation has improved, actions such as overfishing had deteriorated.

“There are no more pristine reefs left in Indonesia,” said Dr Mous.

Source: FT (John Aglionby in Jakarta)