Threatened arthropods are defined here as any of a number of species within the phylum Arthropoda, whose extinction is likely in the foreseeable future. Estimating the number of threatened arthropod 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,[2] "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.[3]
Arthropods as a group have been very successful organisms on this planet, comprising over half of all the higher life forms. However the expansion of human activities 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.