Coral bleaching impacts 98 of Great Barrier Reef Study

BRISBANE: Coral bleaching has affected 98 per cent of Australia's Great Barrier Reef since 1998, leaving just a fraction of the world's largest reef system untouched, according to a study published Thursday (Nov 4).

The paper in the peer-reviewed journal Current Biology found that just 2 per cent of the vast underwater ecosystem had escaped impacts since the first mass coral bleaching event in 1998 - then the world's hottest year ever, a record that has repeatedly been broken as climate change accelerates.

Lead author Terry Hughes, from the ARC Centre of Excellence for Coral Reef Studies at James Cook University, said the frequency, intensity and scale of climate-fuelled marine heatwaves that cause coral bleaching are increasing.

"Five bouts of mass bleaching since 1998 have turned the Great Barrier Reef into a checkerboard of reefs with very different recent histories, ranging from 2 per cent of reefs that have escaped bleaching altogether, to 80 per cent that have now bleached severely at least once since 2016," he said.

Bleaching occurs when healthy corals become stressed by spikes in ocean temperatures, causing them to expel algae living in their tissues which drains them of their vibrant colours.

The Great Barrier Reef has suffered three mass bleaching events during heatwaves in 2016, 2017 and 2020, leaving many affected corals struggling to survive.

Government scientists said in July that corals have shown some signs of recovery since the last bleaching but admit the long-term outlook for the 2,300km-long ecosystem is "very poor".

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