The Red List Categories and Criteria


The IUCN Red List is regarded as an important barometer of the health of biodiversity, and is explicitly named in the targets set by the international Convention on Biological Diversity. Key to the authority of the Red List is its use of a standardized method for evaluating a defined measure of conservation concern: a species’ risk of extinction within a short period of time. This standardized system, the Red List Categories and Criteria, evaluates the available data on a species’ distribution, population status and threats against each of five Criteria (A-E), to determine its risk of extinction.

 

Each species on the IUCN Red List falls into one of nine assessment categories. Three of these – Vulnerable, Endangered, and Critically Endangered – are explicitly defined by quantitative thresholds given in the IUCN Red List Criteria and are termed “threatened” categories, indicating a high to very high risk of extinction in the near future. The remaining categories define species that do not fall within the categories defined by the Criteria for one of several reasons. The full set of categories is as follows:

 

Least Concern (LC): This species has had its conservation status evaluated and it does not qualify for a threatened listing, for Near Threatened, it is not Extinct, and there is sufficient information to conclude that it is not likely to fall within a threatened category if more data become available. Widespread and abundant species fall within this category, as do species of some conservation concern that are nonetheless at little or no immediate risk of extinction.

 

Near Threatened (NT): This species has had its conservation status evaluated and it does not qualify for a threatened listing, but comes close to meeting the Criteria for a threatened category and/or is likely to qualify for a threatened listing in the near future.

 

Vulnerable (VU): This species has had its conservation status evaluated and the available evidence indicates that falls within the Vulnerable category applying one or more of the Criteria A-E. This species is determined to be at high risk of extinction.

 

Endangered (EN): This species has had its conservation status evaluated and the available evidence indicates that falls within the Endangered category applying one or more of the Criteria A-E. This species is determined to be at very high risk of extinction.

 

Critically Endangered (CR): This species has had its conservation status evaluated and the available evidence indicates that falls within the Critically Endangered category applying one or more of the Criteria A-E. This species is determined to be at extremely high risk of extinction. In some cases the species may already be extinct but available data cannot confirm this or insufficient time has passed since its last sighting to make this determination with confidence, in which case it will be Critically Endangered – Possibly Extinct.

 

Extinct in the Wild (EW): This species survives in captivity, under cultivation, or as naturalized populations outside its natural range, but is no longer known to survive within its natural range and habitat as determined by exhaustive surveys over a time period appropriate for its life cycle.

 

Extinct (EX): There is no reasonable doubt that the last individual of this species has died, as determined by exhaustive surveys within its range and habitat over a time period appropriate for its life cycle.

 

Data Deficient (DD): There is inadequate information to make a direct or indirect assessment of this species’ risk of extinction based on its distribution and/or population status. The species may genuinely be very poorly-known, or it may be well-known but the available information is not in a form that allows its risk of extinction to be determined. Future research into this species may reveal that a threatened status is appropriate, or alternatively that it is not appropriate.

 

Not Evaluated (NE): This species has not yet had its risk of extinction evaluated against the Criteria. Typically Not Evaluated species are not included in the published Red List, however there may be exceptions.

 

The IUCN Red List Categories and Criteria were extensively reviewed between 1997 and 1999. The revised Categories and Criteria were adopted by IUCN Council in February 2000 and the revised system came into use in 2001. All assessments submitted to the IUCN Red List must use this system.

 

A presentation summarising the use of the Categories and Criteria, with worked examples, can be downloaded here.

 

User Guidelines:
Guidelines on how to use the IUCN Red List Categories and Criteria have been developed and these can be downloaded from the Red List website.

 

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