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coral-eating starfish, storms and ocean acidification causing a rapid decline, according to a study

coral cover on the Great Barrier Reef has been reduced by more than half over the last 27 years, according to scientists, following major storms, bleaching and predation by explosions population coral starfish absorbs nutrients away.

At the current rate of decline, new coral cover halved in ten years, but scientists said the reef could recover if the crown of thorns starfish can be controlled and longer-term the global carbon emissions of carbon dioxide is reduced.

"This new study provides compelling evidence that the cumulative impacts of storms, the crown of thorns starfish (COTS) and two bleaching events have had a devastating effect on the reefs in the last three decades, "said John Gunn, Executive Director of the Australian Institute of Marine Science.

Coral reefs are an important part of the marine ecosystem as a source of food and protection for young fish. They are under threat worldwide effects of bleaching due to rising ocean temperatures and increased ocean acidification, which reduces the ability of corals to build their calcium carbonate structures.

The Great Barrier Reef is the largest coral reef in the symbolic world, declared by UNESCO as a World Heritage site and the source of A5bn $ (£ 3.2bn) a year to the Australian economy through tourism. The observations are based on the decline over 2,000 surveys of 214 reefs between 1985 and 2012. The results showed a decrease in coral cover from 28% to 13.8% - an average of 0.53% per annum and a total loss of 50.7% for the period of 27 years. The study was published Monday in the Proceedings of the National Academy of Sciences journal (subscription).

two thirds of the coral loss has occurred since 1998 and the rate of decline has increased in recent years, an average of approximately 1.45% per year since 2006. "If the trend continues, coral cover could halve again in 2022," said Peter Doherty, a researcher at the institute.

tropical cyclones, Cots predation and bleaching 48%, 42% and 10% of the estimated losses. Over the past seven years, the reef was hit by six major hurricanes. Cyclone Hamish, for example, ran along the reef parallel to the coast for about 930 miles (1500 km), leaving a trail of destruction far greater than the average of cyclones, which usually crosses the barrier on a road perpendicular to the coast.

"Corals are notoriously difficult to propagate in captivity and therefore trade remains heavily dependent on the collection in the wild.". "

said the survey results of the Great Barrier Reef are not surprising and challenge environmentalists was localized threats to coral limit a chance to recover and strengthen resilience to the effects of climate change. "It's hard, but quite feasible and there are many community projects around the world that demonstrate this."

Corals can recover if given the chance. But it is slow - in the absence of cyclones, cots and bleaching, Great Barrier Reef can grow back at a rate of 2.85% per year, wrote the scientists. Removing the coral cover problem Cribs increase to 0.89% per annum.