Once a breathtaking sight for divers to behold, Australia's Great Barrier Reef has now turned mostly white.
All but 7 per cent of the World Heritage site has been hit by mass bleaching, which is likely to destroy half the coral, say Australian scientists. The phenomenon takes place when the water is too warm, and mildly bleached coral can recover if the temperature drops. Otherwise, the coral dies.
Scientists believe that the underlying cause of mass bleaching is climate change.
"We've never seen anything like this scale of bleaching before. Our estimate, at the moment, is that close to 50 per cent of the coral is already dead or dying," says Professor Terry Hughes, conveyor of the National Coral Bleaching Taskforce, which conducted aerial surveys of the site.
The Great Barrier Reef is the world's largest living ecosystem that stretches 2,300km along Australia's north-east coast.
Says Australian Environment Minister Greg Hunt: "There were some who said that the worst had passed. We rejected that, and they were wrong. Let it be known that this is a significant event. We take it seriously."