Severe and widespread coral reef damage during the 2014-2017 Global Coral Bleaching Event
Data from 15,066 reef surveys during 2014–2017 show that ocean warming caused the most severe global coral bleaching event on record, with widespread bleaching and mortality predicted across more than half of the world’s reefs. Results reveal accelerating and potentially irreversible degradation of coral ecosystems under ongoing marine heatwaves.
Subject Tags
- Reefs
- Climate impacts
- Climate risks
Abstract
Ocean warming is increasing the frequency, extent, and severity of tropical-coral bleaching and mortality. During 2014–2017, marine heatwaves caused the Third Global Coral Bleaching Event. We analyze data from 15,066 reef surveys globally during 2014–2017. Across all surveyed reefs, 80% and 35% experienced moderate or greater (affecting >10% of corals) bleaching and mortality, respectively. We assess the global extent of coral bleaching and mortality by applying bleaching response curves calibrated from surveyed reefs to predict bleaching globally, based on comprehensive remote-sensing of heat stress. These models predict that 51% and 15% of the world’s coral reefs suffered moderate or greater bleaching and mortality, respectively, during one or multiple years, surpassing damage from any prior global coral bleaching event. Our findings demonstrate that the impacts of ocean warming on coral reefs are accelerating, with the near certainty that ongoing warming will cause large-scale, possibly irreversible, degradation of these essential ecosystems. With heat stress levels during this event surpassing those observed previously, the National Oceanic and Atmospheric Administration developed more extreme Bleaching Alert levels that are now being used during the ongoing Fourth Global Coral Bleaching Event.
Citation
Eakin, C. M., Heron, S. F., Connolly, S. R., Devotta, D. A., Liu, G., Geiger, E. F., ... & Shedrawi, G. (2026). Severe and widespread coral reef damage during the 2014-2017 Global Coral Bleaching Event. Nature Communications, 17(1), 1318.
TNC Authors
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Denise Perez
Spatial Ecologist, Caribbean Div • Caribbean
The Nature Conservancy
Email: denise.perez@tnc.org