Summary
A Nature reassessment classified 340 of 774 reef-building coral species with sufficient data as threatened under IUCN Red List criteria. The estimates rely partly on projected bleaching risk and coral-cover trends because species-level population trends are unavailable for most corals.
A reassessment of reef-building corals published in Nature on 15 October 2026 classified 340 of the 774 species with enough data to assess as threatened under IUCN Red List criteria. That is 44% of the assessable species—not a prediction that those corals will go extinct, or a count of species already lost.
The categories were 33 species classified as Critically Endangered, 251 as Endangered and 56 as Vulnerable. Most were placed in threatened categories because of the risk of population decline linked to projected thermal stress.
How the researchers assessed risk
The research team revisited 892 reef-building coral species that had first been assessed in 2008. For most, species-level population trends were unavailable. Instead, the researchers inferred population reductions using two proxies over three decades: trends in global coral cover and projected annual severe bleaching under the SSP2-4.5 scenario. They adjusted those estimates using traits thought to affect each species’ vulnerability.
This approach combines observed changes in coral cover with climate-based projections and species characteristics. It offers a way to assess risk where direct population data are lacking, but means the results are estimates of relative risk rather than direct measurements of every species’ population decline.
The IUCN Red List assigns categories by comparing information such as population size, decline and geographic range against standardised thresholds. Its categories describe species’ relative extinction risk; they do not predict whether or when a particular species will go extinct.
Why the assessment matters
Coral reefs support ecological functions and provide economic and social benefits in more than 100 tropical countries. The assessment highlights how warming threatens both coral biodiversity and the functioning of reef ecosystems. Climate-driven warming is a primary threat to reefs and is increasing the frequency of global bleaching events.
The researchers note that their findings predate the three hottest years on record and the fourth global coral bleaching event, which occurred from 2023 to 2025. They also predate the first exceedance of the 1.5°C global-warming threshold in an annual mean. The assessment therefore describes the risk estimated from its inputs, not a reassessment incorporating those subsequent events.
The authors say future assessments would benefit from more species-level population data, better coverage of coral ranges, and measures of thermal stress and recovery that reflect conditions across those ranges. Those data could make estimates of risk more specific to individual species and locations.