Australia's Great Barrier Reef has lost 50% of its coral since the mid-1980s, much of that because of a ravenous species of starfish that can each consume some 12 square yards (10 square meters) of coral in a year, scientists reported Tuesday.
According to a study by the Australian government's Institute of Marine Sciences and the University of Wollongong, the coral cover on the world's largest coral reef ecosystem suffered damage from tropical cyclones (48%), the crown-of-thorns starfish (42%), and coral bleaching (10%).
If current trends continue, the reef will lose another 50% of its coral in the next 10 years, the scientists said.
Stopping the starfish infestation is the one thing humans can do that can save the reef, they said.
"We can't stop the storms, and ocean warming (the primary cause of coral bleaching) is one of the critical impacts of the global climate change," John Gunn, chief executive officer of the institute, said in a press release. "However, we can act to reduce the impact of crown of thorns."
"The study shows that in the absence of crown of thorns, coral cover would increase at 0.89% per year, so even with losses due to cyclones and bleaching there should be slow recovery," Gunn said in the release.
Reacting to the study, the World Wildlife Fund said Australia must reduce fertilizer runoff as a first step to controlling the crown-of-thorns starfish.