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Threatened species are any species (including animals, plants, fungi, etc.) which are vulnerable to endangerment in the near future. Species that are threatened are sometimes characterised by the population dynamics measure of ''critical depensation'', a mathematical measure of biomass related to population growth rate. This quantitative metric is one method of evaluating the degree of endangerment. ==IUCN definition== The International Union for Conservation of Nature (IUCN) is the foremost authority on threatened species, and treats threatened species not as a single category, but as a group of three categories, depending on the degree to which they are threatened: *Vulnerable species *Endangered species *Critically endangered species 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-listed species, as they are listed in the IUCN Red List of Threatened Species. Subspecies, populations and stocks may also be classified as threatened. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Threatened species」の詳細全文を読む スポンサード リンク
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