How to Read the IUCN Red List
What “Vulnerable”, “Endangered” and “Data Deficient” actually mean — and why they appear on every Biosphere record.
By Biosphere Editorial Team · 2026-06-30
The IUCN Red List of Threatened Species, started in 1964, is the world’s most widely used source of information on the extinction risk of animals, plants and fungi. More than 160,000 species have now been assessed.
The categories
| Category | Code | Meaning |
|---|---|---|
| Least Concern | LC | Widespread or abundant; not currently at risk |
| Near Threatened | NT | Close to qualifying for a threatened category |
| Vulnerable | VU | High risk of extinction in the wild |
| Endangered | EN | Very high risk of extinction in the wild |
| Critically Endangered | CR | Extremely high risk of extinction in the wild |
| Extinct in the Wild | EW | Survives only in cultivation or captivity |
| Extinct | EX | No reasonable doubt that the last individual has died |
Not enough data
Data Deficient (DD) means there is not enough information to assess the risk — not that the species is safe. The orca is listed as Data Deficient globally because its populations differ so much from one another. Species that have not been assessed yet are Not Evaluated (NE).
How species are assessed
- How fast the population is declining
- How small the geographic range is
- How small the population is
- Quantitative analyses of extinction probability
A species only needs to meet one set of criteria to be listed. You can filter the Catalog by any of these categories.