Overview
- The synthesis reports that 51% of the world’s coral reefs experienced moderate or worse bleaching in 2014–2017, with about 15% showing significant mortality.
- Scientists combined NOAA Coral Reef Watch heat‑stress data with in‑water and aerial observations from more than 15,000 surveys across 41 countries.
- Nearly 200 co‑authors from 143 institutions contributed, enabling the first rigorous global calculation of bleaching and mortality from the Third Global Bleaching Event.
- NOAA introduced more extreme Bleaching Alert levels after unprecedented heat stress during 2014–2017, and those alerts are now guiding the response to the ongoing Fourth Event.
- The Fourth Global Coral Bleaching Event began in early 2023 and is still unfolding, with impacts reported in Florida, the Caribbean, Australia’s Great Barrier Reef and the Pacific, including documented mortality on Panama’s Pacific coast.