Nearly every assessed shallow-water coral reef ecosystem faces high risk of collapse by 2075, IUCN says

As of 8:41 a.m. ET, Thursday, Oct. 22, 2026

Nearly every assessed shallow-water coral reef ecosystem on the planet faces an "extremely high risk of collapse by 2075," with 96% classified as Critically Endangered, the International Union for Conservation of Nature (IUCN) said Thursday, Oct. 22, in a global coral reef assessment under its Red List of Ecosystems.

The analysis covers all coral reef ecosystems in warm, shallow waters, spanning 127 tropical and subtropical ecoregions and 188,362 square kilometers of coral reefs, according to the IUCN. The world's largest and most biodiverse reef ecosystems, including those within the Great Barrier Reef in Australia, the Coral Triangle in the western Pacific Ocean and Southeast Asia, the Mesoamerican Barrier Reef System and the Red Sea coral reefs, are all Critically Endangered, the highest level of threat, the IUCN said.

"Coral reefs are one of the clearest vital signs of the ocean's health. They support a quarter of all marine species and serve as an early warning system for the state of the seas," said Dr Grethel Aguilar, IUCN Director General.

"It is not too late to give coral reefs a chance to recover, but it requires decisive action to tackle climate change and halt further ocean warming," Aguilar said.

Heat stress the most consistent threat

The IUCN said heat stress from climate change is "the single most consistent threat driving coral reef decline worldwide," with ocean warming and marine heatwaves causing mass bleaching events that trigger widespread coral mortality with increasing frequency. The assessment used the Intergovernmental Panel on Climate Change's "middle-of-the-road" scenario, which projects 2.7°C of atmospheric warming by the end of the century.

Overexploitation of key fish groups, such as parrotfish and grouper, is a major current threat in several regions, including East Asia, the Western Indian Ocean, the Caribbean and Brazil, threatening 63% of coral reef ecosystems, the IUCN said. It also named coastal development, pollution, overtourism, industrial development, aquaculture, more frequent storms, freshwater flooding and crown-of-thorns starfish outbreaks as significant threats.

A coral reef ecosystem collapses when it loses its defining features, the IUCN said: hard corals almost disappear, and algae, rubble and sponges take over.

A narrowing window

Based only on observed changes over the past 50 years, and excluding future climate projections, 24% of coral reef ecosystems would be Critically Endangered rather than 96%, according to the IUCN. On observed changes alone, 20% of coral reef ecosystems in East Asia would be Critically Endangered, and reefs in the Northern Red Sea would be classified as Vulnerable, the IUCN said.

"The risk of coral reef collapse is escalating, but this must be a wake-up call rather than a cause for despair. Coral reefs have shown a remarkable ability to bounce back from devastating bleaching events," said Dr Mishal Gudka, Research Director at CORDIO East Africa and scientific lead of the global IUCN Red List of Coral Reef Ecosystems assessment.

The Western Galápagos Islands have been classified as Collapsed since the 1982-83 El Niño event, and four of the 127 ecoregions are Data Deficient, according to the IUCN, which said the Critically Endangered share would otherwise cover all assessed coral reefs.

The assessment was coordinated by the IUCN, the IUCN Commission on Ecosystem Management, the University of Melbourne and CORDIO East Africa, with regional nodes of the Global Coral Reef Monitoring Network, and brought together more than 250 experts covering reefs in more than 80 countries and territories, the IUCN said. Separately, the IUCN said it recently reassessed 892 reef-building coral species on its Red List of Threatened Species and found that 44% are threatened with extinction.

What is not known

The status of the four ecoregions listed as Data Deficient was not determined, and the IUCN's release does not name them. The 2075 projections rest on a single climate scenario, and the release does not say how the results would differ under higher or lower warming.