The IUCN Red List has a long-established history as the world's most comprehensive information source on the global conservation status of plant and animal species. It is based on an objective system of assessing the risk of extinction for a species.

Species listed as Critically Endangered, Endangered or Vulnerable are collectively described as threatened.The IUCN Red List is not just a register of names and associated threat categories.

It is a compendium of information on the threats to the species, their ecological requirements, where they live, and information on conservation actions that can be used to reduce or prevent extinctions.

Although only 2.7 percent of the world's 1.8 million described species have been assessed so far, the IUCN Red List provides a useful snapshot of what is happening to species today and highlights the urgent need for conservation actionBirds are the best known group with less than one percent of species classified as Data Deficient,meaning that we do not have enough information to say if they are threatened or not.

However, for many groups, we cannot say what the situation is for a large proportion of species and many of them could well be threatened: 47 percent of 1,045 species of sharks and rays, 35 percent of marine mammals and 24 percent of amphibians are Data Deficient.