Almost half of warm-water reef-building coral species are at risk of extinction, conservationists have warned after a global assessment announced at the UN climate conference.

The conservation status for all 892 species was analysed for the International Union for Conservation of Nature’s (IUCN) Red List of threatened species ahead of Cop29 in Azerbaijan.

The corals are found in shallow, warm-water habitats and form the colourful reefs seen in tropical and sub-tropical ocean areas. Built over tens of thousands of years, coral reefs are the most biodiverse of marine ecosystems.

The IUCN analysis released on Wednesday showed that 44% are threatened – up from a third in 2008 when reef-building corals were last assessed for the Red List.

It comes as world leaders gather this week in Baku for negotiations on cutting emissions and tackling climate change, which remains the top threat to reef-building corals.

Dr Grethel Aguilar, IUCN director general, said: “This global coral assessment vividly illustrates the severe impacts of our rapidly changing climate on life on Earth and drives home the severity of the consequences.

“Healthy ecosystems like coral reefs are essential for human livelihoods, providing food, stabilising coastlines and storing carbon.

“The protection of our biodiversity is not only vital for our well-being but crucial for our survival.

“We must take bold, decisive action to cut greenhouse gas emissions if we are to secure a sustainable future for humanity.”

In addition to climate change, corals are affected by severe bleaching events, pollution, agricultural runoff, disease and unsustainable fishing.

The assessments considered the most recent status update on coral reefs from the Global Coral Reef Monitoring Network (GCRMN) and Intergovernmental Panel on Climate Change (IPCC) data for future warming scenarios.

Among the species analysed were staghorn coral and elkhorn coral – two “critically endangered” species in the Caribbean that have experienced significant declines due to increased warming, water pollution, hurricanes and the severe impacts of coral diseases.

IUCN co-ordinator Beth Polidoro said: “By acting now, we can slow the pace of ocean warming and broaden the window of opportunity for corals to potentially adapt and survive in the long term.

“This is not just about preserving the spectacular beauty of coral reefs.

“Coral ecosystems also sustain coastal fishing communities, stabilise the shoreline and coastal habitats, and help remove carbon from the ocean, among other benefits.”

Cutting greenhouse gas emissions is the main solution to saving corals from extinction, accompanied by actions to address other threats to strengthen species’ resilience, the IUCN said.

The assessors also recommended more research into if and how corals can adapt to warmer waters, with evidence of limited adaptation so far.

The global assessment of reef-building corals includes 85 Atlantic species highlighted in a PLOS One journal article also published on Wednesday. Atlantic coral species are particularly highly threatened due to annual severe bleaching events, pollution and the impacts of disease.

Red List assessments of cold-water corals, which are found in colder, deeper waters around the world and do not depend on sunlight, are ongoing, with threats including fishing activity, especially bottom trawling, deep sea mining, drilling for oil and gas, or laying of deep-sea cables.