IUCN Red List categories

The International Union for Conservation of Nature and Natural Resources (IUCN) maintains the Red Data Book, also called the Red List, which records the conservation status of plant and animal species worldwide. When a species is completely wiped out, it is said to be extinct (for example, the dinosaurs); when the number of individuals of a species starts steadily declining, it is said to be endangered. After thorough evaluation, IUCN places each assessed species into one of nine categories: Extinct (EX) -- the last known individual has died or has not been recorded for a very long time; Extinct in the Wild (EW) -- surviving members exist only in captivity; Critically Endangered (CR) -- an extremely high risk of extinction, with very few individuals (around 50) surviving; Endangered (EN) -- a very high risk of extinction, reflected in a rapid population decline of roughly 50 to over 70 percent over the previous ten years or three generations; Vulnerable (VU) -- a high risk of extinction with a population decline of roughly 30 to over 50 percent over the same period; Near Threatened (NT) -- close to qualifying as threatened, or likely to do so in the near future; Least Concern (LC) -- widespread and abundant after careful assessment; Data Deficient (DD) -- inadequate data available to properly judge extinction risk; and Not Evaluated (NE) -- among the roughly 1.9 million described species that IUCN has not yet formally assessed. …