Great Barrier Reef bleaching outbreak damages two-thirds of site

Record-breaking temperatures driven by global warming have bleached two-thirds of the Great Barrier Reef, scientists say. Aerial surveys show a 900-mile stretch of the Australian reef is badly bleached - which occurs when stressed corals lose algae and turn white. Bleached corals can recover if the temperature drops and algae repopulates, but researchers say global warming threatens to make the problem irreversible. It is feared large swathes of the World Heritage-listed area may not recover from the latest outbreak, which follows a severe instance in 2016 and is the fourth mass bleaching since 1998.

Bleached corals are not necessarily dead corals, but in the severe central region we anticipate high levels of coral loss. It takes at least a decade for a full recovery of even the fastest growing corals, so mass bleaching events 12 months apart offers zero prospect of recovery for reefs that were damaged in 2016

Dr James Kerry, who led the aerial surveys

In recent years, farm pollution, development and an outbreak of the coral-eating crown-of-thorns starfish has worsened conditions in the Great Barrier Reef. Meanwhile, several reefs around Queensland’s Whitsunday Islands were destroyed or badly damaged by a category four cyclone last month. Authorities which opened a review into the damage have found pulverised coral at popular snorkelling spots. Professor Terry Hughes, director of the institute which carried out the aerial studies, said: “Clearly the reef is struggling with multiple impacts. Without a doubt the most pressing of these is global warming. As temperatures continue to rise the corals will experience more and more of these events.” He added: “Ultimately, we need to cut carbon emissions, and the window to do so is rapidly closing.”