The Great Barrier Reef has experienced its most widespread coral bleaching on record, according to a recent Australian government report. The Australian Institute of Marine Science surveyed the health of the reefs between August 2024 and May 2025 and found the “most spatially extensive” bleaching since records began in 1986, primarily driven by climate change-induced heat stress. Coral cover declined by almost one-third, down to 26.9 percent, in the southernmost third of the reef, with the southern reefs experiencing their highest recorded levels of heat stress.
The study’s authors noted that “the declines in the north and south were the largest in a single year since monitoring began 39 years ago.” AIMS CEO Professor Selina Stead emphasized that mass bleaching events are becoming more intense and frequent, stressing that “the future of the world’s coral reefs relies on strong greenhouse gas emissions reduction.” Managing local pressures and helping reefs adapt to and recover from climate change impacts is also crucial.
Coral bleaching occurs when corals are stressed by rising ocean temperatures, causing them to expel the microscopic algae that live in their tissues. Without these algae, corals lose their vibrant colors and become more susceptible to disease and mortality. The primary cause of regional or mass bleaching is increased sea temperatures, with other factors like poor water quality, pollution, and increased ultraviolet radiation contributing to the severity of bleaching.
The Great Barrier Reef, a 2,300km expanse of tropical corals housing a stunning array of biodiversity, is home to over 1,500 species of fish, 4,000 types of molluscs, and 240 species of birds. The reef’s decline could have significant economic and environmental implications, including decreased tourism revenue and loss of coastal protection.
Richard Leck from the World Wildlife Fund compared the fluctuating health of the Great Barrier Reef to a “rollercoaster,” highlighting the need for ambitious and rapid climate action to prevent further decline. AIMS researcher Mike Emslie emphasized that the reef is “still worth fighting for,” but urgent action is necessary to protect it. Conservation efforts include reducing greenhouse gas emissions, improving water quality, and establishing marine protected areas.
The Australian government’s report highlights the importance of addressing climate change to protect the Great Barrier Reef. Opportunities for protection include adopting low- and zero-emission alternatives and stronger action on climate pollutants like methane. However, Australia remains a major exporter of fossil fuels, including coal from the Adani coal mine, which is shipped out past the reef.