Nearly all of the world’s shallow-water coral reefs are at an extremely high risk of collapse by 2075, primarily due to climate change, according to a new global assessment by the International Union for Conservation of Nature (IUCN). The organization classified 96 percent of coral reef systems as “critically endangered,” the highest risk category in its evaluation.

Coral reefs are highly sensitive to rising temperatures and are increasingly vulnerable as human-driven climate change warms the oceans and intensifies coral bleaching events. Mishal Gudka, the scientific lead of the IUCN Red List of Coral Reef Ecosystems assessment, emphasized the severity of the threat, stating that climate change presents a “very high risk” to the survival of these ecosystems.

The IUCN unveiled its findings during the United Nations COP17 biodiversity summit in Yerevan, Armenia, where global leaders are being urged to accelerate efforts aimed at halting and reversing biodiversity loss by 2030. The assessment used a “middle-of-the-road” climate scenario from the UN’s Intergovernmental Panel on Climate Change (IPCC), projecting global temperatures to rise by 2.7 degrees Celsius above pre-industrial levels by 2100. Current international commitments place the world on track for a 2.6-degree increase this century, underscoring the urgency of addressing climate impacts on marine environments.

In addition to heat stress, overfishing is identified as a significant factor harming coral reefs, particularly through the depletion of key herbivorous and predatory fish species such as parrotfish and groupers. These species help regulate algae growth, which is essential for maintaining coral ecosystem balance. Other threats include coastal development, pollution, tourism pressures, and more frequent severe storms.

The assessment covered 127 coral reef systems spanning 188,362 square kilometers, including some of the largest and most biodiverse reefs worldwide. Among those classified as critically endangered are Australia’s Great Barrier Reef, the Coral Triangle in Southeast Asia and the western Pacific, the Mesoamerican Barrier Reef System in the Caribbean, and reefs in the Red Sea. Coral reef collapse is characterized by the loss of hard corals—the primary architects of reef structures—and their replacement by algae, rubble, and sponges.

While nearly all reefs are projected to be critically endangered by 2075 under climate change scenarios, the IUCN notes that if only historical data from the past 50 years is considered without future climate projections, 24 percent of reef ecosystems would currently fall into this category, illustrating both the rapid pace of decline and the potential impact of future warming.

Gudka highlighted the critical window for conservation and climate action, stressing that decisions made in the coming years will shape whether coral reefs maintain their current form or transform into vastly different, less ecologically valuable systems by the century’s end. IUCN Director General Grethel Aguilar echoed this sentiment, affirming that it is still possible to enable reef recovery with intensified efforts to combat climate change and ecological degradation.