Red Lists are inventories of species that are threatened or at risk of extinction in a given country or region. The criteria of the International Union for Conservation of Nature (IUCN) are used in preparing Red Lists. Using these criteria requires fairly precise knowledge of species distribution, the total number of individuals of the species, and population dynamics. These lists are crucial for nature conservation, and Iceland is one of many countries to maintain national Red Lists for the most common groups of organisms.
Species on Red Lists are grouped into several different risk categorieson the basis of the seriousness of the threats they face. Even common species can end up on a Red List, if their numbers fall dramatically over a short period of time or are at risk of doing so in coming years.
The IUCN maintains Red Lists for plants and animals that are endangered or at risk of extinction on a global basis. As of 2019, over 27,000 biological species are listed on the IUCN Red List of Threatened Species as threatened with extinction.
The Icelandic Institute for Natural History compiles Red Lists for the biota of Iceland. The IINH has published Red Lists for vascular plants, birds, and mammals.