A critically endangered (CR) species is one which has been categorized by the International Union for Conservation of Nature as facing a very high risk of extinction in the wild. It is the highest risk category assigned by the IUCN Red List for wild species.
As the Red List does not consider a species extinct until extensive, targeted surveys have been conducted, species which are possibly extinct are still listed as "critically endangered". IUCN maintains a list of "possibly extinct" CR(PE) and "possibly extinct in the wild" CR(PEW) species, modelled on categories used by BirdLife International to categorize these taxa.
To be defined as critically endangered in the Red List, a species must meet ANY of the following criteria (A–E) ("3G/10Y" signifies three generations or ten years—whichever is longer—over a maximum of 100 years; "MI" signifies Mature Individuals):
- A: Occurring over less than 100 km² and two of:
- 1. Severe habitat fragmentation or existing at just one location
- 2. Decline in extent of occurrence, area of occupancy, area/extent/quality of habitat, number of locations/subpopulations, or amount of MI.
- 3. Extreme fluctuations in extent of occurrence, area of occupancy, number of locations/subpopulations, or amount of MI.
- B: As above, but less than 10 km² (used to show differing levels of severity).
- C: Declining population of less than 250 MI and either:
- 1. A decline of 25% over 3G/10Y;
- 2. Extreme fluctuations, or over 90% of MI in a single subpopulation, or no more than 50 MI in any one subpopulation.
- D: Numbers less than 50 MI.
- E: At least 50% chance of going Extinct in the Wild over 3G/10Y.
- Lists of IUCN Red List Critically Endangered species for lists ordered by taxonomic rank
- Category:IUCN Red List critically endangered species for an alphabetical list
- The World's 25 Most Endangered Primates
- The world's 100 most threatened species
- IUCN for additional information on the IUCN
- "Apes extinct in a generation". BBC. 2005-09-01. Retrieved 2005-09-01.
- IUCN (2014). "Table 2: Changes in numbers of species in the threatened categories (CR, EN, VU) from 1996 to 2014 (IUCN Red List version 2014.2) for the major taxonomic groups on the Red List" (PDF). Retrieved 2014-08-30.
- IUCN (9 Feb 2000). "IUCN Red List Categories and Criteria, Version 3.1" (PDF). Retrieved 2012-12-31.
- List of Critically Endangered Species. IUCN Red List of Threatened Species. Version 2014.2. International Union for Conservation of Nature. 2014. Retrieved 30 August 2014.