New Australian government report finds coral decline across the reef due to ‘climate change-induced heat stress’.
The Great Barrier Reef has suffered its most widespread coral bleaching on record, according to a new Australian government report, as ocean temperatures soared in 2024.
The Australian Institute of Marine Science (AIMS) said on Wednesday that it surveyed the health of the reefs between August 2024 and May 2025 and found the “most spatially extensive” bleaching since records began in 1986, which was “predominantly driven by climate change-induced heat stress”.
Scientists also found that coral cover declined by almost one-third, down to just 26.9 percent, in the southernmost third of the reef, as the southern reefs experienced their highest recorded levels of heat stress.
“The declines in the north and south were the largest in a single year since monitoring began 39 years ago,” the study’s authors wrote in The Conversation publication.
Described as the world’s largest living structure, the Great Barrier Reef is a 2,300km (1,400-mile) expanse of tropical corals that houses a stunning array of biodiversity.
AIMS CEO Professor Selina Stead said that “mass bleaching events are becoming more intense and are occurring with more frequency”.
“The future of the world’s coral reefs relies on strong greenhouse gas emissions reduction,” Stead said.
Managing local pressures and helping the reefs to “adapt to and recover from the impacts of climate change” was also important, she added.
According to UNESCO, which has classified the Great Barrier Reef as a World Heritage Site, the ecosystem is home to the world’s largest collection of coral reefs, including 400 types of coral.
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It is also home to 1,500 species of fish, 4,000 types of mollusc, 240 species of birds, as well as species such as the dugong and the large green turtle, according to UNESCO.
While United Nations experts say the Great Barrier Reef should be included among the World Heritage Sites that are classified as “in danger”, the Australian government has lobbied to keep it off the endangered list, fearing it could affect the billions of dollars in tourism revenue it generates annually.
In a report released last week, Australia’s Climate Change Authority said that opportunities to protect the Great Barrier Reef from climate change include major fossil-fuel exporting countries adopting low- and zero-emission alternatives and stronger action on climate pollutants, such as methane, which “contribute most to near-term climate warming”.
But Australia remains a major exporter of fossil fuels, including coal from the controversial Adani coal mine, which is shipped out past the Great Barrier Reef.
The authority’s report also noted that some 93 percent of the excess heat in the atmosphere has been absorbed by the world’s oceans, and that 2024 ocean temperatures surpassed the previous record set in 2023.