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

Key points

• The IUCN classified 96 percent of the world's shallow-water coral reef systems as critically endangered, its highest risk category.
• The assessment warns that total extinction of these reefs is possible by 2075.
• The IUCN says reefs in most parts of the world are not yet lost and can still recover from bleaching.

A new assessment by the International Union for Conservation of Nature (IUCN) warns that 96 percent of the world's shallow-water coral reef systems face an extremely high risk of collapse within the next 50 years. The report, released on Thursday, placed those reefs in the "critically endangered" category, the IUCN's highest risk level, with total extinction possible by 2075.

The IUCN, described as the world authority on threatened wildlife, examined 127 tropical and subtropical coral systems covering 188,362 square kilometres. It based its projections on the UN climate panel's middle-of-the-road scenario, which forecasts global temperatures rising 2.7C above pre-industrial levels by 2100.

Why reefs are at risk

Corals are heat-sensitive and especially vulnerable to human-driven climate change, which is warming the oceans and making damaging bleaching events more frequent and intense. Mishal Gudka, scientific lead of the IUCN Red List of Coral Reef Ecosystems assessment, said the emergence this year of a "super" El Nino also presents a risk to corals. He spoke at a news conference at the UN's COP17 biodiversity summit in Yerevan, Armenia.

When a reef collapses, hard corals disappear and are replaced by algae, rubble and sponges, leaving the reef unable to support a diverse ecosystem that can range from tiny invertebrates to reef fish such as grouper. Reefs are important sources of seafood and tourism and often act as buffers against coastal erosion and storms. They support a quarter of marine species as well as coastal communities and businesses.

Coral reefs have shown a remarkable ability to bounce back from devastating bleaching events

— Mishal Gudka

Which reefs are affected

Most of the world's famous reef systems are critically endangered, according to the assessment, including the Great Barrier Reef in Australia, the Coral Triangle in the Western Pacific Ocean and Southeast Asia, the Mesoamerican Barrier Reef System and the Red Sea coral reefs.

The report follows other recent warnings. A week earlier, another IUCN study in the journal Nature found that nearly 44 percent of reef-building coral species face an elevated extinction risk from climate change. A year ago, a survey found harmful bleaching had spread to 84 percent of the ocean's reefs, the most intense on record.

What officials said

Despite the warning, the IUCN said coral reefs in most parts of the world "are not yet lost". Gudka said reefs have shown a strong ability to recover from devastating bleaching events and that resilient pockets can still remain in the future.