IUCN classifies 96% of assessed reefs as critically endangered

The International Union for Conservation of Nature has classified 96% of assessed shallow-water coral reef ecosystems as critically endangered, warning that nearly all face an extremely high risk of collapse by 2075 under projected climate conditions. The first global assessment of coral reefs under the IUCN Red List of Ecosystems examined 127 tropical and subtropical reef systems covering 188,362 square kilometres. The classification concerns the risk of whole ecosystems collapsing, not the extinction risk of individual coral species. The assessment’s outlook is based on a middle-range climate pathway projecting global temperatures 2.7 degrees Celsius above preindustrial levels by 2100. If researchers instead consider observed changes over the previous 50 years and exclude future climate projections, 24% of reef ecosystems would be classified as critically endangered, the IUCN said. An ecosystem is considered collapsed when living reef-building hard corals largely disappear and are replaced by algae, rubble and sponges. Hard corals form the structure that supports the broader reef habitat, so their loss can affect the marine life that depends on it. The IUCN identified...