Nearly half of reef-building coral species threatened with extinction, assessment finds

A global reassessment by the International Union for Conservation of Nature has found that 44% of reef-building coral species with sufficient data for assessment are threatened with extinction, up from about one-third in 2008.

The union announced the findings Oct. 15. Its Species Survival Commission’s Coral Specialist Group reviewed all 892 reef-building coral species on the IUCN Red List of Threatened Species, using data and expertise from more than 60 coral experts worldwide.

Of the 774 species with enough data to assess, 340 fell into the threatened categories: 33 are critically endangered, 251 are endangered and 56 are vulnerable.

“The crisis facing corals is deadly serious. If we don’t take swift action to curb climate pollution, we could lose half of them forever,” said Miyoko Sakashita, oceans director at the Center for Biological Diversity. “We’ve already seen a lot of disruptions to sea life from the much warmer waters El Nino has brought this year, and I’m really worried about what that will do to threatened coral species. Coral reefs are the backbone of the ocean and we can’t have a healthy marine ecosystem without them.”

The assessment uses data through 2020. The authors warn that the share of corals at risk is likely higher now, because the assessment predates the 2023–2025 global coral bleaching event, the fourth on record.

Climate change is the main threat, determining the final status of more than 90% of the species at highest risk, according to the study.

The coral Red List Index, which tracks extinction risk over time, fell from 0.96 before 1998 to 0.89 in 2008 and 0.74 in 2024. A value of 1 means no species face high risk, and 0 means all are extinct. The authors said extinction risk is increasing faster for corals than for any other comprehensively assessed group, including mammals, sharks and rays, birds, amphibians and cycads.

Risk varies by region and coral group. In the Indo-Pacific, 43% of assessed species are threatened, compared with 50% in the Atlantic. Among Indo-Pacific Acroporidae, which include staghorn and plating corals that build much of a reef’s three-dimensional structure, 191 of 279 species, or 68%, were classified as Endangered.

“This assessment provides the most comprehensive evaluation to date of global extinction risk among reef-building corals, and a stark warning of the accelerating increase in global threats to coral reefs,” said David Obura, co-chair of the IUCN Coral Specialist Group and director of CORDIO East Africa.

The authors said every tenth of a degree of avoided warming helps preserve coral diversity and reef function. They called for reducing the drivers of climate change and other causes of reef decline, along with stronger protection and management of resilient reefs.

Francoise Cabada-Blanco, the group’s other co-chair and a professor at the University of Portsmouth, said better data on how corals respond to threats at regional and local levels will improve future assessments and help managers act.

The MSC Foundation funded the research. Its executive director, Daniela Picco, said the findings provide evidence to guide conservation priorities.

Assessments of cold-water corals, which live in deeper, colder waters, are ongoing.