The key facts

  • 44% of reef-building corals are threatened with extinction according to IUCN criteria
  • Of the 774 species with sufficient data, 340 were assessed as threatened: 33 critically endangered, 251 endangered, 56 vulnerable
  • The main cause is thermal stress from climate change; the assessment does not account for the 2023–2025 bleaching event

Scale of the Threat

Nearly 44% of the world's reef-building coral species face an elevated risk of extinction, mainly due to rising ocean temperatures linked to climate change. This is the conclusion of a new study published on Thursday in the scientific journal Nature.

Methodology and Results

The authors assessed 892 species of reef-building corals according to the criteria of the International Union for Conservation of Nature (IUCN) Red List. Of the 774 species for which sufficient data were available, 340 were classified as threatened: 33 critically endangered, 251 endangered, and 56 vulnerable. The research team included scientists from the Australian Institute of Marine Science and the University of Queensland, among other institutions. They analyzed coral population trends and projected thermal stress, updating the 2008 assessment.

The Cause — Thermal Bleaching

The study identified climate-related thermal stress as the primary driver of projected population decline. Reef-building corals are marine animals whose hard skeletons form the foundation of tropical reefs. When water temperatures rise, they can expel the algae living in their tissues, which provide them with nutrients and give them color. This process, known as coral bleaching, leaves them vulnerable to starvation, disease, and death.

The Assessment May Be Understated

The researchers warned that their assessment was conducted before the record ocean warming and the global coral bleaching event of 2023–2025, so the share of species under threat may now be higher. Coral reefs support marine biodiversity and provide food, coastal protection, and livelihoods for more than 100 tropical countries. The scientists emphasized that limiting further warming remains an essential condition for preserving coral biodiversity.