San Francisco Frontiers - Nearly all coral reefs risk collapse in 50 years: IUCN

In the first global assessment of its kind, the world authority on threatened wildlife classified 96 percent of the planet's coral reef systems as "critically endangered" -- its highest risk category.

Corals are heat sensitive and particularly vulnerable to human-driven climate change, which is warming the world's oceans and increasing the frequency and intensity of damaging bleaching events.

"The risk of coral reef collapse is escalating, but this must be a wake-up call rather than a cause for despair," said Mishal Gudka, scientific lead of the IUCN Red List of Coral Reef Ecosystems assessment.

"Coral reefs have shown a remarkable ability to bounce back from devastating bleaching events," said Gudka, who is also research director at Coastal Oceans Research and Development in the Indian Ocean (CORDIO) East Africa, a conservation organisation.

For their assessment, researchers used the "middle-of-the-road" scenario from the UN's panel of climate experts that projects global temperatures rising 2.7C above pre-industrial levels by 2100.

The world is on track for 2.6C warming this century under current global commitments to cut planet-heating emissions, the United Nations warned Wednesday.

"Heat stress from climate change is the single most consistent threat driving coral reef decline worldwide," the IUCN said in a statement.

Overfishing is also hurting corals as certain herbivores and predators help control algae and maintain an ecological balance, the organisation said.

The overexploitation of parrotfish and other groupers threatens 63 percent of coral reef ecosystems.

Coastal development, pollution, tourism and more frequent storms are among other threats.

- Critically endangered coral -

The IUCN's analysis examined 127 tropical and subtropical coral systems covering 188,362 square kilometres.

The world's largest and most biodiverse coral reefs are among those classified as critically endangered -- Australia's Great Barrier Reef, the Coral Triangle in southeast Asia and the western Pacific, the Caribbean's Mesoamerican Barrier Reef System, and the Red Sea coral reefs.

A reef ecosystem collapses when hard corals -- which build its living foundation -- largely disappear and are replaced by algae, rubble and sponges.

The report was released during the UN's COP17 biodiversity summit in Yerevan, Armenia, where governments are under pressure to make progress on a landmark pact to halt and reverse biodiversity loss by 2030.

Despite its warning, the IUCN said coral reefs in most parts of the world "are not yet lost".

If scientists look only at what has happened over the past 50 years, excluding future climate projections, 24 percent of coral reef ecosystems would be deemed critically endangered instead of 96 percent, the IUCN said.

"It is not too late to give coral reefs a chance to recover, but it requires decisive action to tackle climate change and halt further ocean warming," said IUCN Director General Grethel Aguilar.

"We know what is needed: ambitious emissions reductions, stronger protection and restoration efforts, and sustained investment in resilient coastal ecosystems and the communities that depend on them."

A study published in the journal Nature last week found that, by 2020, nearly half of coral species were at "elevated relative risk of extinction", with climate change the main driver of this decline.

A.Evans--SFF