Understanding the Red List

How do species enter the Red List and who decides?
Approved experts assess species based on five quantitative criteria and then classify the species into one of 9 categories in the IUCN Red List.

What do the categories mean?
Of the categories, three are considered to be "threatened categories" (Critically Endangered, Endangered and Vulnerable). Species in these categories are threatened with global extinction and currently, 16,119 species are assessed as threatened.

What are the decisions based upon?
The criteria are based on a combination of biological factors including rate of decline, population size and distribution, and area of geographic distribution (range). For more detail see the Red List Categories and Criteria booklet version 3.1.

The categories defined

• EXTINCT (EX)
  A taxon is Extinct when there is no reasonable doubt that the last individual has died. A taxon is presumed Extinct when exhaustive surveys in known and/or expected habitat at appropriate times throughout its historic range have failed to record an individual.
• EXTINCT IN THE WILD (EW)
  A taxon is Extinct in the Wild when it is known only to survive in cultivation, in captivity or as a naturalized population (or populations) well outside the past range. A taxon is presumed Extinct in the Wild when exhaustive surveys in known and/or expected habitat, at appropriate times throughout its historic range have failed to record an individual.

The threatened categories:

• CRITICALLY ENDANGERED (CR)
  A taxon is Critically Endangered when it is considered to be facing an extremely high risk of extinction in the wild.
• ENDANGERED (EN)
  A taxon is Endangered when it is considered to be facing a very high risk of extinction in the wild.
• VULNERABLE (VU)
  A taxon is Vulnerable when it is considered to be facing a high risk of extinction in the wild.

• NEAR THREATENED (NT)
  A taxon is Near Threatened when it does not qualify for Critically Endangered, Endangered or Vulnerable now, but is close to qualifying for, or is likely to qualify for, a threatened category in the near future without ongoing conservation measures.
• LEAST CONCERN (LC)
  A taxon is Least Concern when it has been evaluated against the criteria and does not qualify for Critically Endangered, Endangered, Vulnerable or Near Threatened. Widespread and abundant taxa are included in this category.
• DATA DEFICIENT (DD)
  A taxon is Data Deficient when there is inadequate information to make a direct, or indirect, assessment of its risk of extinction based on its distribution and/or population status.
• NOT EVALUATED (NE)
  A taxon is Not Evaluated when it is has not yet been evaluated against the criteria.

• NOTE: Critically Endangered (Possibly Extinct) : This is not a new Red List category, but is a flag developed to identify those Critically Endangered species that are in all probability already Extinct but for which confirmation is required (for example, through more extensive surveys being carried out and failing to find any individuals).