8 November 2009

The role of landslides in coral reef destruction

Posted by Dave Petley

Loss of coral reefs is a widely reported and serious problem, caused by a range of factors including changes in sea temperature and chemistry; pollution; fishing; development; and mining. Reefs are often also damaged by severe storms. It is is thus unsurprising to read this report of serious damage to the coral reefs at Orchid Island, to the south-east of Taiwan, as a result of Typhoon Morakot:

“Coral reefs off Taiwan will need up to 100 years to recover from Typhoon Morakot, which lashed the island in early August killing more than 600 people, a scientist said Tuesday…Some of the shallow-water coral reefs look as if they’ve been crushed by road rollers,” said Chen Chaolun, a researcher at the institution. “They will need up to 100 years to recover.”…The live coral coverage near Orchid Island has tumbled from 68 percent to less than 18 percent, he said.

However, the cause of the damage is a surprise:

“The reefs, popular with diving enthusiasts, were damaged by driftwood thrust into the sea by the typhoon and mudflows crashing into the ocean from coastal areas.”

This driftwood, which accumulated on the beaches of Taiwan and even choked harbours in Japan, was released from the hillsides by the huge numbers of landslides triggered by the typhoon, and then carried out to sea by the rivers. The volume of driftwood was extraordinary, as this Guardian image shows:

I have not seen previous reports of landslide-released driftwood causing coral reef destruction, so this is an interesting new landslide impact.