Official analysis of 124 reefs on the Great Barrier Reef shows coral cover has dropped sharply after a record-breaking marine heatwave in 2024, prompting grave fears over the trajectory of the natural wonder.

Over the past few years, fast-growing corals had pushed the Great Barrier Reef’s coral cover to record highs. But those corals were known to be extremely vulnerable and one bad summer away from losing those gains.

Our new report by the Australian Institute of Marine Science (AIMS) shows these fears have been realised. The percentage of living hard coral covering the Great Barrier Reef’s surface dropped in each region we surveyed.

The recent extreme highs and lows in coral cover are a troubling phenomenon. It raises the prospect that the Great Barrier Reef may reach a point from which it cannot recover.

In healthy corals, tiny algae produce both the coral’s main food source and its vibrant colours. When the water gets too warm, the algae are expelled and the coral’s tissue becomes transparent – revealing the white limestone skeleton beneath. This is called coral bleaching.

Coral can recover if temperatures are reduced and the relationship with the algae is restored, but it’s a stressful and difficult process. And if........

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