Almost Every Shallow Reef Faces Collapse Risk by 2075

Almost all shallow-water coral reef ecosystems face an extremely high risk of collapse by 2075, according to a global IUCN assessment that warns of losses to fisheries and coastal protection. ^[1][2]

The International Union for Conservation of Nature announced the findings on October 22, 2026, alongside the UN Biodiversity Conference in Yerevan, Armenia. It classified 122 of 127 assessed ecosystems as Critically Endangered, the highest risk category before Collapsed. ^[1][2]

These reefs support around a quarter of all marine fish species. Their fisheries feed millions of people, their visitors sustain tourism businesses, and their structures reduce the force of waves, flooding and erosion. The danger extends from life beneath the water to livelihoods and homes along the shore. ^[2]

"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," said IUCN Director General Grethel Aguilar. ^[1]

Most of the assessed reefs still have living coral. The finding describes their risk of losing the features that make them functioning reef ecosystems, rather than a loss that has already happened. Only the Western Galápagos ecosystem is classified as Collapsed, while four others have too little information for a risk classification. ^[1][2]

A future shaped by heat

The assessment covers 188,362 square kilometres of shallow, sunlit reefs in more than 80 countries and territories. The ecosystems classified as Critically Endangered account for 96% of those assessed and 99.8% of their combined reef area. ^[2]

The projected scale of the damage comes into focus when the assessment separates past changes from future warming. Looking only at observed changes over the past 50 years, 30 ecosystems, or 24%, reach the Critically Endangered category. Adding projected heat stress takes that number to 122. ^[1][2][3]

The researchers used a middle-of-the-road emissions scenario from the Intergovernmental Panel on Climate Change, which projects about 2.7°C of global warming by 2100. Under that pathway, IUCN says heat stress alone puts 95% of the reef ecosystems in the Critically Endangered category. ^[1][2]

The year 2075 is therefore a horizon for assessing risk under a specified warming pathway, not an expiry date shared by every reef. The future depends on how much warming occurs and what is done to conserve reefs. ^[1][2]

More than 250 experts worked in 10 regional teams, combining decades of monitoring of corals, algae and fish with satellite measurements of sea-surface temperatures, climate projections and reef maps. The work was coordinated with the University of Melbourne and CORDIO East Africa. ^[1][2]

Each ecosystem receives the highest risk category it reaches under any of five criteria. Those cover past reef loss, restricted distribution, heat stress, disruption of ecological processes and quantitative analysis of collapse risk. A reef does not have to deteriorate equally on every measure to receive the highest warning. ^[2]

The assessment excludes deeper reefs, rocky reefs and cold-water corals. How widely surviving corals can adapt to hotter seas, and which ecosystems will retain the greatest resilience, remain open questions. ^[2]

What a reef loses

Collapse means a change in what the ecosystem is and what it can support. The hard corals that build the reef nearly disappear, and algae, rubble and sponges take over. That replacement reduces habitat and the food webs that depend on it. ^[1][2]

The loss is more substantial than a change in colour. A reef can retain some living coral while losing the defining features of a coral reef ecosystem. Assessment scientific lead Mishal Gudka said resilient pockets of coral could survive into the future. ^[1][2][4]

For fishing communities, the stakes begin with the reef's role as habitat. Alongside its share of marine fish species, it supports many invertebrates. Damage to that living system threatens the resources on which reef fisheries depend for food and livelihoods. ^[2]

For coastal communities, reefs also provide physical protection. By reducing wave energy, they help limit flooding and erosion. Their decline places another service at risk, one that matters even to people who never fish or visit a reef. ^[2]

Tourism adds a further economic exposure. Reefs support local visitor economies, so ecological decline threatens income as well as marine life. Food, jobs and coastal protection are tied to the same ecosystem. ^[2]

Two tasks, on different scales

IUCN identifies heat stress from climate change, including increasingly frequent marine heatwaves and bleaching, as the most consistent global threat to reefs. Its recommendations begin with rapid cuts in greenhouse-gas emissions to limit further ocean warming. ^[1][2]

Local damage compounds that pressure. Overfishing, pollution, sediment and coastal development weaken reefs' ability to recover. The assessment found disrupted balances among corals, algae and fish in 63% of the ecosystems it examined. ^[1][2]

That gives governments and coastal authorities work they can do alongside emissions cuts: clean up coastal waters, make fishing sustainable, strengthen protections and restore damaged reefs. IUCN says reducing those pressures can give reefs a better chance to recover between heatwaves. ^[1][2]

The practical conclusion is to pursue both tasks together. Local conservation gives living reefs a better chance, while emissions cuts address the heat driving the global projection. Treating either as sufficient would leave the other source of damage in place.

Gudka said the findings should be a "wake-up call rather than a cause for despair". ^[1][4] The next policy test is whether countries turn that warning into fishing rules, pollution controls and stronger reef protection, alongside the emissions cuts IUCN says recovery requires. ^[1][2]