Australia declares 'mass bleaching' at Great Barrier Reef

Map of eastern Australia showing the Great Barrier Reef.

Australia's spectacular Great Barrier Reef is suffering "mass bleaching" as corals lose their colour under the stress of warmer seas, authorities said Friday, in a blow widely blamed on climate change.

The world's largest coral reef system, stretching for more than 2,300 kilometres (1,400 miles) along the northeast coast of Australia, is showing the harmful effects of the heat, said the Reef Authority.

The Great Barrier Reef, home to some 1,500 species of fish and 4,000 types of mollusc, was suffering despite the cooling effect of the La Nina weather phenomenon, which is currently influencing Australia's climate, the authority said.

Though bleached corals are under stress, they can still recover if conditions become more moderate, the Reef Authority said.

The mass bleaching report emerged four days after the United Nations began a monitoring mission to assess whether the World Heritage site is being protected from climate change.

UNESCO's mission is to assess whether the Australian government is doing enough to address threats to the Great Barrier Reef -- including climate change -- before the World Heritage Committee considers listing it as "in danger" in June.

He pressed the government to show the damaged areas to the UN mission now inspecting the reef rather than the picturesque areas that have been untouched.

"Here, corals are being cooked by temperatures up to four degrees above average, which is particularly alarming during a La Nina year when ocean temperatures are cooler."

When the UN previously threatened to downgrade the reef's World Heritage listing in 2015, Australia created a "Reef 2050" plan and poured billions of dollars into protection. 

"Unfortunately, as more severe bleaching is reported across our beloved Great Barrier Reef, we can see these devastating events are becoming more common under the continuing high rate of greenhouse gas emissions," she said.

- 'No safe limit' -

An average increase of 1.5 degrees Celsius above pre-industrial levels would see more than 99 percent of the world's coral reefs unable to recover from increasingly frequent marine heatwaves, they reported in the journal PLOS Climate.

"The stark reality is that there is no safe limit of global warming for coral reefs," lead author Adele Dixon, a researcher at the University of Leeds' School of Biology, told AFP.

The 2015 Paris Agreement enjoins nearly 200 nations to keep global heating "well below" 2C.

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Originally published as Australia declares 'mass bleaching' at Great Barrier Reef