Almost all shallow-water coral reefs now face extinction risk, study warns

Almost all of the world's shallow-water coral reefs face an extremely high risk of collapse within the next 50 years, the International Union for Conservation of Nature has warned.

In a report released on Thursday, the world authority on threatened wildlife classified 96 percent of all coral reef systems as "critically endangered." Its analysis examined 127 tropical and subtropical reef systems covering 188,362 square kilometres, using the middle-of-the-road climate scenario from the UN's panel of climate experts.

Corals are highly sensitive to heat and particularly vulnerable to human-driven climate change, which is warming the oceans and making bleaching events more frequent and intense. The emergence of a "super" El Nino this year adds to the danger. When a reef collapses, hard corals vanish and are replaced by algae, rubble and sponges.

The stakes are enormous. Often called the "rainforests of the sea," coral reefs hold some of the richest biodiversity on Earth and are critical sources of seafood and tourism income. The systems at risk include the Great Barrier Reef off Australia, the Coral Triangle in the western Pacific and Southeast Asia, and the Mesoamerican Barrier Reef.

Despite the grim outlook, the IUCN stressed that reefs in most parts of the world "are not yet lost," noting that coral reefs have shown a remarkable ability to recover from devastating bleaching events.