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Endangered arthropods are defined here as any of a number of species within the phylum Arthropoda, whose extinction is likely in the foreseeable future (e.g. within one human generation). Estimating the number of arthropod endangered species is extremely difficult, primarily because a vast number of the species themselves are not yet named or described. Furthermore, according to Deyrup and Eisner: "The rate of destruction and degradation of natural habitats is currently so great that there are not nearly enough biologists to even catalog the arthropod species that are suddenly on the edge of extinction." In any case, independent estimates indicate that there are millions of undocumented arthropods on Earth.〔(''Southern Appalachian Information Node: Resources about Arthropods'' )〕 Arthropods as a group have been very successful organisms on this planet, comprising over half of all the higher life forms. However the expanding human population has led to demise of many arthropod species through the mechanisms of deforestation, conventional farming, slash-and-burn methods in the tropics, habitat fragmentation via urban development, excessive use of pesticides and even the success of forest fire suppression. The social/political practice whereby a species is given a formal designation as "Endangered" or "Protected" is a different matter, called "Conservation status", and discussed elsewhere; see Endangered Species List for the United States, and IUCN Red List for international purposes. Only a tiny fraction of the planet's endangered arthropods are formally recognized as such, as no one has ever evaluated the conservation status of the vast majority of arthropod species. ==Difficulty of estimating numbers of species== It is difficult to estimate the total number of endangered arthropod species, since many of the taxa themselves have not been recorded. For example, in North America the estimated number of insect species exceeds 163,000, of which only about two thirds are taxonomically known. An even greater discovery awaiting, over 72 percent of North American arachnids are yet to be named and described.〔 The total number of living arthropod species is probably in the tens of millions.〔 One conservative estimate puts the number of arthropod species in tropical forests alone at six to nine million species.〔Chad Arment, ''Cryptozoology: Science and Speculation'', 393 pages. ISBN 1-930585-15-2 (2004)〕 As a consequence of all of the above, most published estimates of the total number of endangered insects and arachnids are probably low by at least an order of magnitude.〔 Conservatively at least eighty percent of all living animal species are arthropods.〔( Anna Thanukos, ''The Arthropod Story'', University of California, Berkeley )〕 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「Endangered arthropods」の詳細全文を読む スポンサード リンク
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