|By risk of extinction|
Extinct in the Wild (List)
|Critically Endangered (List)
|At lower risk|
|Conservation Dependent (List)
Near Threatened (List)
IUCN Red List
International Union for Conservation of Nature
Lists of organisms by population
Data Deficient (DD) is a category applied by the IUCN, other agencies, and individuals to a species when the available information is not sufficient for a proper assessment of conservation status to be made. This does not necessarily indicate that the species has not been extensively studied; but it does indicate that little or no information is available on the abundance and distribution of the species. The IUCN recommends that care be taken to avoid classing species as Data Deficient when the absence of records may actually indicate dangerously low abundance: "If the range of a taxon is suspected to be relatively circumscribed, if a considerable period of time has elapsed since the last record of the taxon, threatened status may well be justified" (see also precautionary principle).
See also 
- "The Categories," in IUCN (1994).
- IUCN (1994). "1994 Categories & Criteria (version 2.3)". 2006 IUCN Red List. Retrieved 2006-12-17.[dead link]