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How Does an Animal Get Put on the Endangered List?

Endangered animal lists can be found at the United Nations Environmental Programme World Conservation Monitoring Centre (UNEP-WCMC) and the International Union for Conservation of Nature (IUCN). Both gather and evaluate global scientific data, develop the endangered lists, and provide guidance for conservation. The three levels of endangerment are vulnerable (10 percent risk of extinction within 100 years), endangered (20 percent risk of extinction within 20 years or five generations) and critically endangered (50 percent risk of extinction within 10 years or three generations).

Population Reduction
- Some species produce more than three generations within 10 years. Population reduction studies cover a 10-year or three-generation period, whichever is greater for the species under study. The studies incorporate declines from the last 10 years or three generations and estimates for the next 10 years or three generations. A species receives a classification of vulnerable with a 20 percent reduction; endangered with a 50 percent reduction; and critically endangered with an 80 percent reduction.
Extent of Occurrence
- The extent of occurrence (number of species traveling through one square km) or the area of occupancy (number of species living in one square km) plus a decline in the habitat size and quality, number of mature individuals, and the numbers of a subpopulation comprise this criterion. A species is called vulnerable with 20,000 extent of occurrence or 2,000 area of occupancy; endangered with less than 5,000 extent of occurrence or less than 500 area of occupancy; and critically endangered with less than 100 extent of occurrence or less than 10 area of occupancy.
Population Estimates
- A vulnerable species has less than 10,000 mature individuals combined with an estimated decline of 10 percent within 10 years or three generations. An endangered species has less than 2,500 mature individuals with a continuing estimated decline of at least 20 percent within five years or two generations. A critically endangered species has less than 250 mature individuals and an estimated decline of at least 25 percent within three years or one generation.
Quantitative Analysis
- The quantitative analysis is a calculation of the probability that a species will become extinct in a certain number of years. The statistical data evaluates the characteristics, environment and health of the species. A species receives a classification of vulnerable with a 10 percent probability of extinction within 100 years, endangered with a 20 percent probability of extinction within 20 years or five generations, and critically endangered with a 50 percent probability of extinction within 10 years or three generations.

Nature