New drone footage shows 97% of coral is dead in northern Great Barrier Reef

Bleaching event, which follows a similar one last summer, is fifth in eight years after parts of reef subjected to extreme heat stress

At least 97 per cent of corals on a reef in the northern section of the Great Barrier Reef have died during one of the most severe bleaching events ever recorded.

The discovery was made by scientists from multiple institutions who used high-resolution drone imagery to monitor the reef near the Lizard Island.

“At least 97 per cent of the corals had died over those three months. We were there to do our sea cucumber monitoring work, but there was silence amongst us nine researchers,” said Professor Jane Williamson, a marine biologist at Macquarie University, who analysed the coral deaths at North Point reef on Lizard Island with her colleagues.

She said she was “horrified” after seeing the analysis. “We came out of the water and didn’t know what to say. It’s an iconic reef and most of it was dead,” she added.

Drone footage taken in March showed widespread bleaching and fluorescing corals, but by June, nearly all the corals had died.

This bleaching event, which follows a similar one last summer, was the fifth in eight years and subjected parts of the reef to extreme heat stress.

Bleaching refers to a phenomenon where corals lose their vibrant colours and turn white, normally due to changes in temperature. Coral reefs are among the most diverse ecosystems on Earth, providing habitat and food for a vast array of marine species.

The footage collected by scientists is the first quantitative assessment of coral mortality from this mass bleaching event.

Four experts independently assessed the state of each coral in set areas on North Point Reef.

“We don’t know how much coral died beyond this reef. But we do know that, according to other aerial surveys, almost one-third of the Great Barrier Reef experienced “very high” and “extreme” levels of coral bleaching last summer,” the scientists wrote in The Conversation.

The scientists are calling for more studies to assess the coral mortality.

The evidence comes after Unesco had urged the Australian federal government to release data on the extent of coral mortality as soon as possible.

Environment minister Tanya Plibersek recently announced that Unesco would not list the Great Barrier Reef as a “world heritage site in danger,” but Unesco has called for Australia to improve its climate action plans and land management practices.

“[Australia] is urged to make mortality rates public as soon as possible,” the Unesco report said.

Dr Lyle Vail, the director of the Australian Museum’s Lizard Island Research Station, said the development was heartbreaking.

“It’s pretty heartbreaking to lose all that coral recovery,” he said.