The Great Barrier Reef has recorded its biggest annual drop in live coral in two of the three areas monitored since 1986, according to a new report from the Australian Institute of Marine Science (Aims). The study is the first to comprehensively document the devastating impacts of the early 2024 mass coral bleaching event, the most widespread and severe on record for the reef.
In the northern section, between Cooktown and the tip of Cape York, coral cover fell by 25 per cent due to bleaching, two cyclones and associated flooding. The southern section, from Mackay to just north of Bundaberg, saw a 30 per cent decline. Both represent the highest annual drops on record. The central section suffered a 13 per cent fall, having escaped the worst of the heat in 2024.
Dr Mike Emslie, who leads the long-term reef monitoring programme at Aims, described the findings as 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. "This volatility is very likely a sign of an unstable system." In the months following the bleaching, scientists reported a "graveyard of corals" around Lizard Island, and a separate study recorded the death of 40 per cent of corals at One Tree Island.
Emslie noted that coral cover had reached record levels in some places before 2024, driven by fast-growing acropora corals that are more susceptible to heat stress. However, that recovery has now been undone, with cover mostly back in line with long-term averages. Widespread mass bleaching was first observed on the Great Barrier Reef in 1998 and has occurred repeatedly since, with events in 2002, 2016, 2017, 2020, 2022, 2024 and 2025.
The Aims report comes a month before the Australian federal government is due to announce its 2035 emissions reduction target. Last week, the Climate Change Authority emphasised the importance of holding warming as close to 1.5°C to protect the reef. Richard Leck, head of oceans at WWF Australia, called on the government to set a target consistent with 1.5°C, saying: "This is the one action the government can take to give the reef a fighting chance."
