Of 774 assessable reef-building corals, 340 qualify as threatened under IUCN criteria
A Nature reassessment of 892 reef-building coral species classifies 340 of the 774 assessable ones, 44%, as threatened under IUCN Red List criteria. The findings predate the fourth global bleaching event of 2023-2025, as the authors themselves note.
The Scientist · Science desk
Two bars, each out of 892 reassessed reef-building coral species: 340 classified as threatened, and 118 that lacked sufficient data to be assessed.
- Threatened, of all reassessed, claim 14 340 of 892 species 38% computed
Threatened, of all reassessed The rest of the 892
- Lacked data to be assessed, claim 13 118 of 892 species 13% computed
Lacked data to be assessed The rest of the 892
| Share | Part | Whole | Percent | Claim |
|---|---|---|---|---|
| Threatened, of all reassessed | 340 species | 892 species | 38% (computed) | 14 |
| Lacked data to be assessed | 118 species | 892 species | 13% (computed) | 13 |
What happened
- Of the 340 threatened species, 33 were assessed as Critically Endangered, 251 as Endangered and 56 as Vulnerable.
- Species-level population trends are unavailable for most reef-building corals, so the authors inferred declines from global coral cover trends and projected severe bleaching under SSP2-4.5, adjusted for trait-based vulnerability.
- Most of the threatened listings come from risk of population reduction tied to projected thermal stress.
- The authors add that the findings also predate the three hottest years on record and the first annual-mean exceedance of the 1.5C warming threshold.
Why it matters
- What's now possible capability The species-level workbook lists projected decline, past cover decline and vulnerability trait scores for each species, so outside analysts can check which input drives a given category.
- What it limits constraint Until species-level population data and recovery metrics exist, the categories are only as fine-grained as global cover trends and a single warming scenario; the authors name those data as what future assessments need.
- What it limits constraint A comparison with 2008 has to use the recalculated 2008 categories in the supplement, which separate genuine from non-genuine changes in classification.
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The 44% is a share of the species with enough data. Subtract the 774 assessable species from the 892 reassessed and 118 species lacked sufficient data [13]. Divide the 340 threatened species by all 892 and the share is 38% [14]. Count all 118 unassessed species as threatened and it is 51% [15]. The share for the whole group lies between those two figures.
The decline figures behind the categories are inferred from proxies, so the listings are model outputs [5]. The assessment does not measure how many of the 340 species are losing individuals right now [2]. The Red List sorts species by comparing population size, decline and geographic range against standardised thresholds [8]. Obura and colleagues write: "The Red List does not predict whether or when a species may go extinct." [9]
On whether the picture is now worse, the authors state that the work predates the fourth global bleaching event of 2023-2025 [6]. The thermal-stress input is a projection under SSP2-4.5 over three decades [5]. The abstract estimates neither what that event would do to the count nor how much of the recent heat the projection had already assumed.
We'd expect an update to raise the count, on one condition: that the 2023-2025 heat shows up in the cover-loss or projected-bleaching inputs that drive the categories [5]. The size of any change, and which species would cross a threshold, would come only from re-running the classification.
What to watch
- A re-run of the classification that folds in 2023-2025 bleaching and cover data; it would show whether the 340 moves.
- Species-level population data and thermal-stress and recovery metrics, the inputs the authors say future assessments need.
- Data on the 118 species that currently lack enough information to be assessed.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence78
- Adoption
- Not scored
- Hype gap+12
- Incentives
- Not scored
- Confidence76
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
Obura and colleagues reassessed the IUCN Red List status of 892 reef-building coral species, first assessed in 2008.
- [2]
Of the 774 species with sufficient data to be assessed, 340 (44%) were classified as threatened under IUCN Red List criteria.
- [3]
Thirty-three species were assessed as Critically Endangered, 251 as Endangered, and 56 as Vulnerable.
- [4]
Most of the threatened listings were due to risk of population reduction associated with projected thermal stress.
- [5]
Because species-level population trends are unavailable for most reef-building corals, population reductions were inferred using proxies based on global coral cover trends and projected annual severe bleaching under SSP2-4.5, both over three decades, adjusted using trait-based estimates of species vulnerability.
- [6]
The findings predate the fourth global coral bleaching event (2023-2025).
- [7]
The findings also predate the three hottest years on record and the first exceedance, for an annual mean, of the 1.5C global warming threshold.
- [8]
The Red List assesses the relative extinction risk of species, placing them in categories of increasing risk by comparing their population size, decline and geographic range against standardised thresholds.
- [9]
"The Red List does not predict whether or when a species may go extinct."
- [10]
As the ranges of coral species remain under-surveyed, future assessments would be strengthened by species-level population data and thermal-stress and recovery metrics that better capture range-representative dynamics.
- [11]
The supplementary workbook gives, for each of the 892 species, projected population decline under SSP2-4.5, past coral cover decline (GCRMN), and scores for each vulnerability trait, along with the Red List category and criteria for 2024.
- [12]
The workbook includes recalculated Red List categories for 2008 and pre-1998, and the supplementary text describes methodological updates from the 2008 assessment and reports genuine and non-genuine changes in classification.
- [13]
118 of the 892 reassessed species lacked sufficient data to be assessed.
- [14]
Measured against all 892 reassessed species, the 340 threatened species are about 38%.
- [15]
If all 118 unassessed species were also threatened, 458 of 892 species, about 51%, would be threatened.
Sources
2 independent publishers whose own reporting we read for this story.
- nature.comNearly half of reef-building corals face elevated relative risk of extinction
1 article · October 14, 2026
- phys.orgNearly half of reef-building coral species face higher risk of extinction
1 article · October 15, 2026
Topics and entities
Entities
- Francoise Cabada-Blanco
- International Union for Conservation of Nature
- IUCN SSC Coral Specialist Group
- IUCN Red List
- Nature
- University of Portsmouth