Coral reefs worldwide are more than half bleached, study says damage may be irreversible

A global analysis of more than 15,000 reefs found 51% experienced moderate-or-worse bleaching and 15% showed significant mortality; Australian aerial surveys also report widespread bleaching on the Great Barrier Reef.

A new multi-year analysis and recent aerial surveys report widespread coral bleaching across the world’s reefs. The study, published Feb. 10 and led by a team including NOAA oceanographer C. Mark Eakin and James Cook University’s Sean R. Connolly, assessed data from more than 15,000 reefs collected over a three-year period. Researchers described the period studied as the Third Global Bleaching Event (2014–2017) and noted that a more severe Fourth Global Bleaching Event began in early 2023. Australian authorities have confirmed a widespread bleaching event on the Great Barrier Reef through recent aerial observations. Key findings: - The study found 51% of assessed reefs sustained "moderate or worse" bleaching. - About 15% of reefs in the analysis experienced significant mortality. - The analysis covered more than 15,000 reefs using data across a three-year span tied to the Third Global Bleaching Event (2014–2017). - Researchers and NOAA reported widespread heat stress across the Atlantic, Pacific and Indian oceans and noted an ongoing Fourth Global Bleaching Event that began in early 2023. Summary: The reported findings describe extensive bleaching and notable mortality across a large share of the world’s coral reefs, and Australian aerial surveys confirm widespread bleaching on the Great Barrier Reef. Undetermined at this time.