Great Barrier Reef in fourth mass bleaching event since 2016

The Great Barrier Reef is the world's most extensive coral reef system but has been under increasing stress from the climate crisis [File: Sarah Lai/AFP]

Australia’s Great Barrier Reef, the world’s most extensive coral reef system, is in the midst of a mass bleaching event.

“Coral bleaching has been observed at multiple reefs in all four management areas, confirming a mass bleaching event, the fourth since 2016 and despite La Nina conditions,” the Great Barrier Reef Marine Park Authority (GBRMPA) said in a statement on its website on Friday after carrying out a series of aerial surveys of the 2,300km (1,400 miles) long reef.