The IUCN (International Union for Conservation of Nature) Red List is an inventory of the global conservation status and extinction risk of a wide range of organisms, focussing on animals, plants and fungi. It is used by conservationists, policymakers and researchers to provide an objective assessment of species' status and as a basis for prioritizing conservation actions.
To date, more than 166,000 species have been assessed by the IUCN. The current goal is to have a total of 260,000 species assessed and reassess 142,000 of those species already assessed to ensure that their status is up to date. While an incredible achievement, it is still small compared to some recent estimates of total species numbers of 7.7 million for animals, possibly three to five million for fungi and likely far more than the 300,000 described species for plants.
Species are evaluated using five quantitative criteria: rate of population decline, geographic range, population size, restricted area of habitat, and quantitative analyses indicating extinction probability. They are then categorized into nine groups: not evaluated, data deficient, least concern, near threatened, vulnerable, endangered, critically endangered, extinct in the wild, and extinct.
This project confirms that biodiversity is declining rapidly, with more than 46,300 of the total 166,000 species on the list already threatened with extinction, including 12 percent of birds, 26 percent of freshwater fishes, 26 percent of mammals, 34 percent of conifers, 37 percent of sharks and rays, 38 percent of trees, 41 percent of amphibians and 44 percent of reef building corals.