TOWNSVILLE, Australia — The Great Barrier Reef has endured the most extensive coral bleaching event ever documented along its 2,300-kilometre length, according to the 2026 Annual Reef Health Assessment released Thursday by the Australian Institute of Marine Science (AIMS) and the Great Barrier Reef Marine Park Authority (GBRMPA).
The joint report, based on aerial and in-water surveys of 412 reefs conducted between November 2025 and March 2026, found bleaching across 91 percent of reefs assessed, eclipsing the previous record of 84 percent set in the 2023–24 summer. Hard coral cover declined on 71 percent of surveyed reefs, with the northern sector recording an average drop of 6.4 percentage points and the far-northern sector 8.1 points. Coral mortality in the worst-hit northern and far-northern sectors is provisionally estimated at 38 percent of colonies surveyed, with some inshore reefs near Lizard Island losing more than two-thirds of their hard coral cover. Juvenile coral densities on the northern shelf fell to 3.2 recruits per square metre, the lowest reading since monitoring began.
"This is the most geographically widespread bleaching event we have ever recorded on the Great Barrier Reef," said Dr. Mike Emslie, who leads the AIMS Long-Term Monitoring Program. "We are seeing severe heat stress accumulate in waters that historically served as thermal refuges, including reefs south of Mackay that had largely escaped previous mass bleaching, and juvenile coral densities have collapsed across multiple sectors."
Sea surface temperatures across the marine park averaged 1.7°C above the 1985–2010 baseline through February, with maximum accumulated heat stress reaching 14 degree heating weeks on the northern shelf — well above the 8 DHW threshold associated with widespread mortality. Although the Bureau of Meteorology declared a weak La Niña in February, sea surface temperatures in the Coral Sea have remained 1.4°C above the 2015–2024 average due to persistent marine heatwave conditions.
GBRMPA Chief Scientist Dr. Roger Beeden said the findings would prompt an immediate review of reef management measures. "The ecological window for recovery is narrowing rapidly," Dr. Beeden told reporters in Townsville. "We are now planning emergency interventions to buy time before the next thermal stress event arrives."
Federal Environment Minister Tanya Plibersek announced that an additional A$180 million from the Reef 2050 Plan would be redirected toward expanded larval reseeding at 14 priority sites and accelerated crown-of-thorns starfish culling across the central region over the next 18 months. UNESCO confirmed it would convene a special session in June to reconsider the reef's World Heritage status in light of the findings. Tourism operators in Cairns, Port Douglas and the Whitsundays reported a 22 percent drop in forward bookings for the May–September season following the report's release, according to the Association of Marine Park Tourism Operators.