The Great Barrier Reef has suffered its biggest annual decline in live coral in two of the three regions monitored by scientists since 1986, according to a new report from the Australian Institute of Marine Science.
The survey documented the impact of the 2024 mass bleaching event, described as the most widespread and severe on record for the reef. In the northern section, between Cooktown and Cape York, coral cover fell by 25%, while the southern section, from Mackay to just north of Bundaberg, recorded a 30% decline. The central section, which escaped the worst heat, saw a 13% fall.
Dr Mike Emslie, who leads the long-term monitoring programme, said the results were sobering. 'It has been a pretty sobering year of surveys with the biggest impacts I have seen in the 30-plus years I have been doing this,' he said. He warned that record gains in coral cover, driven by fast-growing acropora corals, had rapidly been reversed, signalling an unstable system.
The 2024 and 2025 events were part of a global mass bleaching episode that affected more than 80% of the world's reefs across at least 82 countries. A separate study found ocean temperatures on the Great Barrier Reef were probably the hottest for 400 years, posing an existential threat to the Unesco-listed site. Mass bleaching has been recorded in 1998, 2002, 2016, 2017, 2020, 2022, 2024 and 2025.
Emslie said the reef was approaching a tipping point where recovery between disturbances becomes impossible. 'We have to mitigate the root causes of the problem and reduce emissions and stabilise temperatures,' he said. The report comes ahead of the federal government's expected announcement of its 2035 emissions reduction target. Richard Leck of WWF Australia urged the government to adopt a target consistent with the 1.5C limit.
