The IUCN Red List of Threatened Species provides a uniform method for assessing how well a species is doing and assigning a conservation status. Here are the basic ideas.
The IUCN Red List
The International Union for Conservation of Nature and Natural Resources (IUCN) has developed a system for categorizing the conservation status of species. It is designed to be applicable to all species of living things and versatile enough that it can be used and understood globally. When it is used, it clears away the confusion created by differing systems of various countries and conservation groups.
Detailed information on species assessment and designation can be found at The IUCN Red List of Threatened Species “2001 Categories and Criteria (version 3.1).” To be included in any category, a species must meet a specific criterion, or one of a short list of criteria that evaluate the condition of the species in the wild. Briefly, here are the categories:
- Extinct (EX): An "Extinct" species is one that is believed to have died out completely. A designation of extinct must be backed up by surveys done in appropriate places at appropriate times. When such surveys turn up no living individuals, the criteria are met.
- Extinct in the Wild (EW): When a species exists only in captivity and exhaustive surveys done in the wild turn up no living individuals, the designation of “Extinct in the Wild” is accepted.
- Critically Endangered (CR): The designation of “Critically Endangered” means a species is threatened with an extremely high risk of becoming extinct in the wild. The risk is assessed based on a severe reduction in population or range, either already observed or reasonably predicted. For comparison with other categories that follow, criterion D is that there are 50 or less mature individuals left. (Larger populations are also critically endangered in specific circumstances)
- Endangered (EN): When a species faces a very high risk of extinction in the wild, it is given the designation of “Endangered.” Like critically endangered species, the risk is evaluated based on known or predicted drops in populations and loss of habitat. For comparison with critically endangered species, described above, criterion D is that the remaining population has 250 or fewer mature individuals.
- Vulnerable (VU): “Vulnerable” species are designated as such when the risk of extinction is high. For comparison with designations described above, criterion D is that the remaining population has 1000 or fewer mature individuals, or that its range is so small or vulnerable that a single catastrophic event could push it into the endangered or critically endangered category very quickly.
- Near Threatened (NT): When a species has been evaluated according to the strict IUCN criteria and does not meet any of them, but nearly meets them, the species is designated as “Near Threatened.”
- Least Concern (LC): Species of “Least Concern” are those that are doing well and do not meet any of the criteria for threatened or endangered species.
- Data Deficient (DD): A species receives the “Data Deficient” designation when there is insufficient information to assess its conservation status. These species may or may not be threatened or endangered in the wild.
- Not Evaluated (NE): A species is “Not Evaluated” when it has not been evaluated according to the IUCN criteria.
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Conservation Status of Species
