Pacific coral reefs are dying at an unprecedented rate, scientists have found. Almost 600 square miles of reef have disappeared every year since the late 1960s - twice the rate of rainforest loss.

Coral loss had become a global phenomenon caused mainly by climate change, rising sea temperatures and man-made nutrient pollution.

©University of North Carolina at Chapel Hill

The study's lead author, John Bruno, said: "We have already lost half of the world's reef-building corals."

The results of the study in the central and western Pacific are published in the open-access journal PLoS ONE. It provides the first regional-scale and long-term analysis of coral loss in the region where relatively little was known about patterns of reef loss.

The Indo-Pacific contains 75 per cent of the world's coral reefs and has the highest coral diversity in the world. High coral cover reefs in the Indo-Pacific ocean were common until a few decades ago, researchers found.

The study, which analysed a database of 6,000 quantitative surveys performed between 1968 and 2004 of more than 2,600 Indo-Pacific coral reefs revealed that reefs are disappearing at a rate of one per cent a year, a decline that began decades earlier than expected.

Historically, coral cover, a measure of reef health, hovered around 50 per cent. Today, only about two per cent of reefs in the Indo-Pacific have coral cover close to the historical baseline.

The survey calculated coral cover, a measure of the ocean floor area covered by living corals which is regarded as a key indicator of reef habitat quality and quantity, similar to measuring an area covered by tree canopy as a gauge of tropical forest loss.

Bruno, associate professor of marine ecology and conservation in the department of marine sciences in UNC-Chapel Hill's College of Arts and Sciences, said the findings would be important to policy makers and resource managers searching for ways to reverse coral loss.

"We can do a far better job of developing technologies and implementing smart policies that will offset climate change," he said.

"We can also work on mitigating the effects of other stressors to corals including nutrient pollution and destructive fishing practices."

Although reefs covered less than one per cent of the ocean globally they played an integral role in coastal communities providing economic benefits through fisheries and tourism.

When corals died - through disease, rising temperatures and nutrient pollution - the benefits quickly disappeared.

Elizabeth Selig, a graduate student in the College of Arts and Sciences' curriculum in ecology, who also helped compile the study, said: "Indo-Pacific reefs have played an important economic and cultural role in the region for hundreds of years and their continued decline could mean the loss of millions of dollars in fisheries and tourism."

The research was funded by a grant by the National Science Foundation and the Environmental Protection Agency's Science to Achieve Results programme.