species, but there are others. For example, the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) (cites.org) classifies endangered species into various appendices, Nature Serve (natureserve.org) maintains lists for the western hemisphere, and the Habitats and Birds Directives list all species of conservation concern in the European Union (https://ec.europa.eu/environment/nature). At a more local level, many national and state governments also maintain lists of species that are threatened within their borders (e.g. https://www.fws.gov/endangered). Sometimes, global categories are used at these local levels (e.g. Quayle et al. 2007), but more often different criteria are used, sometimes leading to very different outcomes (Harris et al. 2012). Most of these organizations also maintain lists of species that are not yet endangered but that are declining and need to be monitored. These have names such as “species of special concern” or “species to watch.” Being on one of these lists does not necessarily translate into conservation action. Issues such as instrumental value (covered in the next section) influence these decisions, as does simple popularity of a species with the public. In particular, it is apparent that endangered animals, especially vertebrates, get far more attention than endangered plants. For example, in the United States 57% of federally listed endangered species are plants, but they receive less than 4% of federal funding for endangered species (Balding and Williams 2016).
BOX 3.1 Categories of the IUCN Red List
The following categories are used by the World Conservation Union to classify species for the IUCN Red List1, a global compilation of species of concern to conservationists.
Extinct (EX)
A taxon is Extinct when there is no reasonable doubt that the last individual has died. The great auk, Carolina parakeet, thylacine, and almost 800 other species are known to have become extinct since 1600.
Extinct in the Wild (EW)
A taxon is Extinct in the Wild when it is known only to survive in cultivation, in captivity, or as a naturalized population well outside the past range. Dozens of species are currently found only in captivity (e.g. the Guam rail and several tree snails) or used to be Extinct in the Wild until they were successfully reintroduced (e.g. the wisent and Przewalski’s horse).
Species that fall in the next three categories are collectively called Threatened. Note that the US Fish and Wildlife Service uses “threatened” as a category of jeopardy one step below “endangered.”
Critically Endangered (CR)
A taxon is Critically Endangered when available scientific evidence indicates that it meets any of the criteria A to E in Box 3.2, and it is therefore considered to be facing an extremely high risk of extinction in the wild. Well‐known examples include the Sumatran, Javan, and black rhinoceroses, the Philippine eagle, California condor, Atlantic sturgeon, and hawksbill turtle.
Endangered (EN)
A taxon is Endangered when available scientific evidence indicates that it meets any of the criteria A to E in Box 3.2, and it is therefore considered to be facing a very high risk of extinction in the wild. Many high‐profile endangered species fall in this group: for example, giant pandas, tigers2, snow leopards, Eastern gorilla, Bornean orangutan, chimpanzees, Asian elephants, blue and fin whales, whooping and Japanese cranes, loggerhead and green turtles, and dawn redwood3.
Vulnerable (VU)
A taxon is Vulnerable when available scientific evidence indicates that it meets any of the criteria A to E in Box 3.2, and it is therefore considered to be facing a high risk of extinction in the wild. Most threatened species are listed as Vulnerable; examples include the lion, cheetah, hippopotamus, sperm whale, snail darter, and most bear species (Asiatic black, polar, sun, sloth, and spectacled).
Near Threatened (NT)
A taxon is Near Threatened when it has been assessed against the criteria and does not qualify for Critically Endangered, Endangered, or Vulnerable now, but is close to qualifying for, or is likely to qualify for, a threatened category in the near future. Also included here are taxa that are the focus of a conservation program, the cessation of which would result in the taxon qualifying for one of the threatened categories. Jaguars and maned wolves are listed as Near Threatened because their status is of some concern, but they do not meet any of the criteria listed below. White rhinos and black caimans are listed as Near Threatened species because their survival depends on conservation programs.
Least Concern (LC)
A taxon is Least Concern when it has been evaluated against the criteria and does not qualify for Critically Endangered, Endangered, Vulnerable, or Near Threatened. Widespread and abundant taxa are included in this category.
Data Deficient (DD)
A taxon is Data Deficient when there is inadequate information to make a direct, or indirect, assessment of its risk of extinction based on its distribution and/or population status. Listing of taxa in this category indicates that more information is required and acknowledges the possibility that future research will show that threatened classification is appropriate. Many mollusks, fishes, and nocturnal birds and mammals have been evaluated, but could not be listed as Threatened because there was not enough information.
Not Evaluated (NE)
A taxon is Not Evaluated when it has not yet been assessed against the criteria. Most of the world’s species, notably all the invertebrates and other small life‐forms, fall into this category.
1 The World Conservation Union maintains the Red List with a consortium of other conservation groups. The wording used here follows that of the IUCN with minor differences. For the exact and latest wording see the Red List website: www.iucnredlist.org.
2 In some cases a species is assigned to one category overall, while various subspecies or populations may be designated differently. For example, tigers are Endangered as a species but the Sumatran and South China subspecies are considered Critically Endangered.
3 The examples used here are dominated by animals because relatively few threatened plant species are widely known.
BOX 3.2 Quantitative criteria for assessing threatened status
The
