First IUCN Global Red List reveals critical risk of collapse for world's coral reefs
ZMT and Universidad de Valle researchers contribute to landmark assessment of coral reef ecosystems in the Eastern Tropical Pacific
The first global IUCN Red List assessment of coral reef ecosystems reveals that 96% are Critically Endangered. Researchers from the Leibniz Centre for Tropical Marine Research (ZMT) contributed scientific data from the Eastern Tropical Pacific, where nine out of ten coral reef ecoregions face a critical risk of collapse and one has already collapsed.
The world's coral reefs are facing an unprecedented threat. According to the first global assessment under the International Union for Conservation of Nature (IUCN) Red List of Ecosystems, published on 22 October 2026, nearly all assessed shallow-water coral reef ecosystems face an extremely high risk of collapse within the next 50 years. Of the 127 coral reef ecoregions assessed worldwide, 122 (96%) are classified as Critically Endangered, four are Data Deficient, and one has already collapsed.
The landmark assessment, presented during the 17th Conference of the Parties to the Convention on Biological Diversity (CBD COP17) in Yerevan, Armenia, brings together the expertise of more than 250 scientists and decades of ecological monitoring data from over 80 countries and territories.
Among the contributors are ZMT reef ecologists Sonia Bejarano and Andrea Arriaga as well as evolutionary ecologist Fernando Zapata from Universidad de Valle in Colombia, who contributed data on coral reef ecosystems in the Eastern Tropical Pacific. Their contributions helped inform the regional assessment and place the ecological challenges facing these reefs within a global context.
Climate change pushes coral reefs towards collapse
The assessment identifies heat stress caused by global warming as the most consistent threat to coral reef ecosystems worldwide. Rising ocean temperatures and increasingly frequent marine heatwaves trigger mass coral bleaching and mortality, leaving reefs with insufficient time to recover between extreme events.
The results are particularly alarming because they account for projected future climate change. Based solely on observed changes over the past 50 years, 24% of coral reef ecosystems would be classified as Critically Endangered. When projected heat stress over the next 50 years is included, this figure rises to 96%.
The assessment uses the IPCC's intermediate emissions scenario (SSP2-4.5), which projects approximately 2.7°C of atmospheric warming by the end of the century.
Coral reefs are among the planet's most biodiverse ecosystems, providing habitats for a vast range of marine organisms and supporting fisheries, coastal protection and tourism. Their collapse would therefore have far-reaching consequences for marine biodiversity and millions of people who depend on healthy reefs.
Eastern Tropical Pacific: resilient reefs reaching their limits
The Eastern Tropical Pacific is a region characterised by high environmental variability and unfavourable conditions for coral reef development. Nonetheless, reefs occur patchily throughout most of the region.
Although the researchers would expect them to be highly vulnerable, reefs here have, in fact, been remarkably resilient. This resilience, however, appears to have its limits, as illustrated by the disappearance of coral reefs from the Western Galápagos following the 1982–83 El Niño warming and coral bleaching event. This should serve as a warning about the consequences of continued global warming, which is the main threat facing coral reefs today, the scientist stressed.
Sonia Bejarano, head of ZMT working group Reef Systems: “Coral reefs in the Eastern Tropical Pacific are naturally small and isolated, yet resilient. Our assessment points at heat stress associated to ongoing global warming as their primary threat, followed by the small area they occupy. Preventing further collapse hinges on reducing greenhouse gases globally, controlling sources of local reef damage, and strengthening regionally coordinated climate-adaptation planning.”
Western Galápagos: a warning from the past
The region of the Western Galápagos, however, paints an even more concerning picture providing a particularly striking example of the long-term consequences of extreme ocean warming. According to the IUCN Red List of Ecosystems assessment, the Western Galápagos is the only coral reef ecoregion in the world classified as Collapsed.
“Although the term collapsed may sound rather final, it does not mean that the region has lost its ecological or conservation value”, explains Andrea Arriaga from ZMT. “On the contrary, although its coral reefs largely disappeared following the extreme warming of the 1982–83 El Niño, the Western Galápagos remains home to hundreds of marine species, many of them endemic, and retains immense conservation value.”
Fernando Zapata stresses: “As another potentially extreme El Niño unfolds in 2026, the lesson from the Western Galápagos is clear: even resilient ecosystems have limits, and their collapse can have consequences that persist for decades.”
A critical window for action
Despite the alarming findings, the assessment emphasises that most coral reef ecosystems have not yet collapsed. Many still contain living corals and retain the potential to recover if the pressures affecting them can be reduced.
The IUCN identifies rapid reductions in greenhouse gas emissions as the most important measure to limit future coral reef collapse. At the same time, effective local conservation remains essential. Reducing pollution, improving fisheries management, protecting reef habitats and strengthening ecological monitoring can help improve reef resilience.
The Global Red List of Coral Reef Ecosystems provides a scientific baseline for assessing ecosystem collapse risk, identifying conservation priorities and monitoring future changes.
For the Eastern Tropical Pacific, the findings underline the need for coordinated conservation across national boundaries and continued scientific collaboration.
The contributions of ZMT researchers to this first global assessment highlight the importance of regional ecological knowledge and long-term monitoring in understanding the future of coral reefs worldwide. It also highlights the current collaboration between ZMT and its partners in Colombia within the COLDEMAR cooperation initiative between Colombia and Germany that brings together technical, scientific and institutional capabilities to address the global climate crisis.
More information:
IUCN press release: Virtually all coral reef ecosystems face high risk of collapse in 50 years: https://iucn.org/press-release/202610/virtually-all-coral-reef-ecosystems-face-high-risk-collapse-50-years-iucn-red
IUCN: Red List of Coral Reef Ecosystems – Results and regional assessments: https://iucn.org/story/202610/red-list-coral-reef-ecosystems
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