Nearly 70% of corals at the UNESCO-listed Ningaloo Reef, Western Australia, have died.
The loss is caused by Australia’s longest and most intense marine heatwave on record.
Coral mortality across eight northern lagoon sites now exceeds 60%.
Out of 1,600 corals counted in March 2025, only about 600 survived by October 2025.
Some resilient species, like Veron’s tube coral and lesser knob coral, survived, but dominant species such as staghorn corals and thin bird’s nest coral died.
Coral reefs support one-third of marine species globally, so mass mortality threatens overall marine biodiversity.