It is the fourth time in six years that such severe and widespread damage – caused by warm sea temperatures – has been detected.
Only two mass bleaching events had ever been recorded until 2016.
Scientists say urgent action on climate change is needed if the world’s largest reef system is to survive.
There are particular concerns that this bleaching event has occurred in the same year as a La Niña weather phenomenon. Typically in Australia, a La Niña brings cooler temperatures…