Nearly all shallow-water coral reef systems worldwide face an extremely high risk of collapse by 2075, according to a new assessment by the International Union for Conservation of Nature (IUCN), which identified warming oceans and marine heat waves as the leading drivers of decline.
The assessment, released on the sidelines of a United Nations biodiversity conference in Albania, found that 96 per cent of shallow-water reef systems are already critically endangered, the highest level of threat in the IUCN classification. It covers 127 tropical and subtropical ecoregions and 188,362 square kilometres of coral reefs globally.
Several of the world’s best-known reef systems, including Australia’s Great Barrier Reef, the Coral Triangle in the Western Pacific and Southeast Asia, the Mesoamerican Barrier Reef System and the Red Sea coral reefs, were identified as critically endangered.
The assessment is the first global IUCN Red List of Coral Reef Ecosystems evaluation of its kind. Mishal Gudka, its scientific lead, said the risk of reef collapse was escalating but added that surviving and resilient pockets of coral could remain if they receive effective protection.
“Coral reefs have shown a remarkable ability to bounce back from devastating bleaching events,” Gudka said. “Pockets of surviving, resilient coral reefs can still remain in the future, so we must do everything within our reach to set them up for success.”
The findings have direct implications for coastal areas because reefs act as buffers against erosion and storms while supporting fisheries, tourism and marine biodiversity. Coral reefs support about a quarter of marine species and underpin the livelihoods of coastal communities and businesses.
When a reef collapses, hard corals are replaced by algae, rubble and sponges. The altered ecosystem can no longer support the same diversity of marine life, including small invertebrates and reef fish such as grouper.
The IUCN described climate change as the “single most consistent threat driving coral reef decline worldwide”. The warning comes after a separate IUCN study published in the journal Nature found that nearly 44 per cent of reef-building coral species face an elevated risk of extinction because of climate change.
Another survey conducted a year earlier found that harmful bleaching had affected 84 per cent of the world’s coral reefs, the largest such event recorded. The assessment also linked the worsening outlook to rising ocean temperatures. The average annual sea surface temperature in ocean areas away from the poles reached a record 20.87 degrees Celsius in 2024, the hottest year recorded globally.
The report’s implications extend to India’s coastal regions. A photograph cited with the assessment showed dead corals along a beach at Kariyachalli Island, off the coast of Thoothukudi in Tamil Nadu, highlighting the condition of reef ecosystems in one of the country’s coral-bearing coastal areas.
Grethel Aguilar, IUCN director general, said coral reefs were among the clearest indicators of ocean health. She called for ambitious emissions reductions, stronger protection and restoration measures, and sustained investment in resilient coastal ecosystems and the communities that depend on them.
The assessment also identified pollution, overfishing and coastal development as pressures that can worsen reef decline. The IUCN’s stated response priorities are reducing global emissions, improving protection and restoration, and supporting coastal communities as governments and conservation agencies respond to the findings.
