96% of the world's coral reef systems critically endangered, IUCN warns
The first global assessment of tropical reef systems found almost all face a very high risk of collapse by 2075, with ocean heat from climate change the main threat.
Almost all of the world's shallow-water coral reefs face an extremely high risk of collapse by 2075, the International Union for Conservation of Nature (IUCN) warned on Thursday. In the first systematic assessment of the planet's 127 tropical and subtropical reef systems, it classed 96% as critically endangered, its highest risk category.
Among those at risk are Australia's Great Barrier Reef, the Coral Triangle of the western Pacific and Southeast Asia, the Mesoamerican Reef and the reefs of the Red Sea. Shallow reefs, which lie up to about 40 metres deep and cover around 188,000 square kilometres worldwide, are home to an exceptional variety of marine life.
"Heat stress from climate change is the single most consistent threat driving coral reef decline worldwide," the IUCN said as it presented the study at the UN's COP17 biodiversity summit in Yerevan, Armenia. When water becomes too warm, corals expel the tiny algae living in their tissues that supply most of their food, which leads to bleaching and often death.
Overfishing is another major pressure, especially the loss of grazing fish such as parrotfish that keep algae in check. The warning comes as the UN says global warming is set to overshoot the 1.5C limit of the Paris Agreement.