A coral bleaching event swept across the Chagos Archipelago in 2024, aligning with the Fourth Global Bleaching Event announced by NOAA and the International Coral Reef Initiative. Findings from a recent report by Mark Spalding (Chief Science Advisor, British Indian Ocean Territory Administration (BIOT)), Marion Bourasseau (Senior Fisheries Protection Officer, Marine Resources Assessment Group (MRAG) and BIOT Administration), with Lindsey Holingsworth (Environment Officer, BIOT Administration), and Isha (University of Plymouth), reveal significant impacts across the region, further underscoring the global urgency of coral conservation.

Between April and June 2024, rising sea temperatures led to widespread bleaching across the Archipelago, with some sites reporting up to 85% of coral affected. Subsequent mortality assessments conducted in November and December showed that, on average, 23% of the region’s live coral cover had been lost. Peros Banhos Atoll suffered the most severe impact, with mortality rates as high as 95% at some sites.

Despite this, there are signs of resilience. In some areas, particularly in Egmont Atoll’s lagoon, corals remained largely unaffected. Observations also confirmed the survival of the critically endangered Chagos brain coral (Ctenella chagius), a positive sign for species conservation. However, recovery remains uncertain, as previous bleaching events have led to long-term coral decline in some areas.

The Chagos Archipelago, largely free from direct human pressures, provides a rare opportunity to study climate-driven coral loss in isolation. The report highlights the need for ongoing monitoring, improved data collection, and enhanced international efforts to mitigate climate change impacts on coral reefs.

As global sea temperatures continue to rise, events like this reinforce the urgent call for action to protect the world’s coral reefs.

Download the “Coral bleaching and mortality in the Chagos Archipelago, 2024” report here.