The Great Barrier Reef has lost half of its coral cover in just 27 years, with most of that decline coming as a result of heavy storms, predation by crown-of-thorn starfish, and coral bleaching caused by warming ocean temperatures. In a comprehensive survey of 214 reefs, researchers at the Australian Institute of Marine Science (AIMS) found that coral cover declined from 28 percent in 1985 to 13.8 percent this year. Intense tropical storms, particularly in the central and southern parts of the reef, have caused about 48 percent of the coral loss, researchers say. An explosion in populations of starfish along the reef caused about 42 percent of the decline; about 10 percent was caused by major bleaching events. Reefs are typically able to regain their coral cover after such disturbances, said Hugh Sweatman, a lead author of the study, published in the Proceedings of the National Academy of Sciences. But recovery takes 10-20 years, he noted. The study found efforts to reduce starfish populations could help increase coral cover at a rate of 0.89 percent per year.