96 Percent of Shallow-Water Coral Reefs Face Extinction Risk

YEREVAN, Armenia — The International Union for Conservation of Nature classified 96 percent of the world's shallow-water coral reef systems as "critically endangered" in a global assessment released Thursday, warning that total extinction is possible by 2075, according to Al Jazeera.

The finding, announced at the United Nations' COP17 biodiversity summit in Yerevan, Armenia, places nearly all tropical and subtropical coral systems in the IUCN Red List's highest risk category. The assessment covered 127 reef systems spanning 188,362 square kilometers, including the Great Barrier Reef in Australia, the Coral Triangle in the Western Pacific and Southeast Asia, the Mesoamerican Barrier Reef System, and the Red Sea coral reefs.

What Does 96 Percent Critically Endangered Mean?

The IUCN Red List uses "critically endangered" as its most severe classification short of extinction in the wild. For coral reef ecosystems, the designation signals an extremely high risk of collapse within the next 50 years absent a change in trajectory. Mishal Gudka, scientific lead of the IUCN Red List of Coral Reef Ecosystems assessment, told reporters at the news conference that the danger is both near-term and structural.

"The future threat of climate change is looming and severe, and that poses a very high risk to the survival of these ecosystems," Gudka said.

The classification does not mean reefs have already collapsed. It means the underlying conditions — primarily ocean warming — have reached a point where collapse is the most probable long-term outcome under current climate projections.

Which Reef Systems Are Most at Risk?

According to the assessment, most of the planet's most recognized reef systems fall into the critically endangered category. That list includes the Great Barrier Reef off the coast of Queensland, Australia; the Coral Triangle, which spans waters off Indonesia, the Philippines, and neighboring states; the Mesoamerican Barrier Reef System along the coasts of Mexico, Belize, Guatemala, and Honduras; and the Red Sea coral reefs bordering Egypt, Saudi Arabia, and other states on that waterway.

These systems are not peripheral to global biodiversity. Coral reefs, sometimes called "rainforests of the sea," support roughly a quarter of all marine species despite covering a small fraction of the ocean floor, and they underpin coastal economies built on fishing and tourism.

Why Is El Nino Compounding the Threat?

Gudka pointed to the emergence this year of a "super" El Nino — the naturally occurring ocean-warming phenomenon — as an additional near-term pressure on already stressed reef systems. Corals are highly sensitive to heat, and sustained warm water triggers bleaching events in which corals expel the algae that give them color and much of their energy. Repeated or prolonged bleaching can kill coral tissue outright.

Human-driven climate change is warming ocean waters broadly and increasing the frequency and intensity of these bleaching episodes, compounding the cyclical stress that El Nino years already bring. The combination, Gudka indicated, is part of what pushed the overall risk assessment into the critically endangered range for nearly all systems studied.

How Was the Assessment Conducted?

The IUCN based its analysis on the "middle-of-the-road" warming scenario used by the UN's Intergovernmental Panel on Climate Change, which projects global temperatures rising 2.7 degrees Celsius above pre-industrial levels by 2100. Researchers applied that scenario across the 127 tropical and subtropical reef systems in the study, assessing each for collapse risk over a 50-year horizon.

The release follows a separate IUCN study published a week earlier in the journal Nature, which found that nearly 44 percent of reef-building coral species face elevated extinction risk — a related but distinct metric measuring species-level vulnerability rather than whole-ecosystem collapse.

What Happens When a Reef Collapses?

A collapsed reef does not simply disappear; it transforms. Hard corals die off and are gradually replaced by algae, rubble, and sponges, according to the assessment. That shift strips away the structural complexity that supports a wide range of species, from small invertebrates to larger reef fish such as grouper.

The practical consequences extend beyond biodiversity loss. Reefs function as physical buffers that reduce the force of storms and coastal erosion, and their collapse removes that protection for the coastal communities and fishing and tourism businesses that depend on them. The IUCN's assessment frames the 96 percent figure as a measure of how widespread that risk has become across reef systems worldwide, with the 2075 extinction threshold marking the point beyond which recovery under current trends would no longer be expected.