- Threatened species
Threatened species are any species (including
animals, plants, fungi, etc.) which are vulnerable to extinctionin the near future. World Conservation Union(IUCN) is the foremost authority on threatened species, and treats threatened species not as a single category, but as a group of three categories: vulnerable, endangered, and critically endangered, depending on the degree to which they are threatened.
Species that are threatened are sometimes characterised by the
population dynamicsmeasure of " critical depensation", a mathematical measure of biomassrelated to population growth rate. This quantitative metric is one method of evaluating the degree of endangerment.
Less-than-threatened categories are
Near Threatened, Least Concern, and the no longer assigned category of Conservation Dependent. Species which have not been evaluated (NE), or do not have sufficient data ( Data Deficient) also are not considered "threatened" by the IUCN.
Although "threatened" and "vulnerable" may be used interchangeably when discussing IUCN categories, the term "threatened" is generally used to refer to the three categories (critically endangered, endangered and vulnerable), while "vulnerable" is used to refer to the least at risk of those three categories. They may be used interchangeably in most contexts however, as all vulnerable species are threatened species ("vulnerable" is a category of "threatened species"); and, as the more at-risk categories of threatened species (namely "endangered" and "critically endangered") must, by definition, also qualify as vulnerable species, all threatened species may also be considered vulnerable.
Threatened species are also referred to as a
red-listedspecies, as they are listed in the IUCN Red List of Threatened Species. Subspecies, populations and stocks may also be classified as threatened.
Endangered Species Actin the United States, "threatened" is the less protected the two protected categories. The Bay checkerspot butterfly("Euphydryas editha bayensis") is an example of a threatened subspecies protected under the ESA.
Biodiversity Action Plan
IUCN Red List
Threatened fauna of Australia
* [http://www.redlist.org/info/categories_criteria IUCN Red List Categories and Criteria]
Wikimedia Foundation. 2010.