IUCN says 96% of shallow-water coral reef systems face critical risk by 2075

Ninety-six percent of the world’s shallow-water coral reef systems face the IUCN’s highest risk category, with many at risk of collapse by 2075, according to the organisation’s first systematic global assessment. The study examined 127 tropical and subtropical reef systems covering about 188,000 square kilometres. The assessment, presented at the United Nations’ COP17 biodiversity summit in Yerevan, Armenia, classifies the reefs as “critically endangered.” The category reflects the projected danger to the ecosystems rather than a finding that almost all reefs have already disappeared.

The IUCN said most reefs are not yet lost. Climate change is the most consistent threat identified in the assessment. Rising ocean temperatures cause corals to expel the microscopic algae that provide much of their nourishment, producing bleaching that can eventually kill them.

Al Jazeera also reported that a newly emerging “super” El Niño could add pressure to already heat-stressed reefs. Other threats include overfishing, particularly of parrotfish and groupers, along with coastal development, pollution, tourism and increasingly severe storms. When hard corals vanish, their structures may be replaced by algae, rubble and sponges, leaving ecosystems able to support fewer species.

The reefs assessed include Australia’s Great Barrier Reef, the Coral Triangle in the western Pacific and Southeast Asia, the Mesoamerican Reef System and coral reefs in the Red Sea. Their decline would affect reef fish, mussels, sea turtles and sharks, as well as coastal communities and businesses that depend on seafood, tourism and protection from erosion and storms. The IUCN used a middle-of-the-road climate scenario from the UN Intergovernmental Panel on Climate Change, projecting global warming of approximately 2.7 degrees Celsius above pre-industrial levels by 2100.

The assessment therefore links the projected risk directly to a future climate pathway rather than only to damage already recorded. The contrast between present conditions and the future projection offers a measure of the remaining opportunity. Based only on changes observed over the past 50 years, 24% of reef systems would qualify as critically endangered.

Including projected climate change raises the figure to 96%. Mishal Gudka, the assessment’s scientific lead, said the next few years would determine whether reefs persist in their familiar form or become different, less valuable ecosystems. IUCN Director General Grethel Aguilar said ambitious emissions reductions, stronger protection and restoration, and sustained investment in resilient coastal ecosystems were needed.

The warning follows other evidence of accelerating pressure. Al Jazeera cited a recent IUCN study finding that nearly 44% of reef-building coral species face an elevated extinction risk linked to climate change. It also reported that a survey a year earlier found bleaching across 84% of the world’s reefs, the most intense episode recorded.

Despite the scale of the assessment, Gudka said surviving pockets of resilient coral could remain and reefs have demonstrated an ability to recover from severe bleaching. The IUCN’s message is therefore both a classification of extreme danger and an argument that conservation and climate action can still influence the outcome.