IUCN Red List
The IUCN Red List is a global assessment system that classifies species by their risk of extinction using standardized criteria and evidence.
IUCN Red List Categories: The standardized labels used to express assessed extinction risk, from Least Concern to Extinct. These categories translate assessment evidence into the risk classifications the Red List publishes.
Species: A basic unit of biological classification, commonly understood as a group of organisms capable of interbreeding. Species are the principal units assessed in the Red List.
Biodiversity conservation: The protection and sustainable management of the variety of life, including variation within species, between species, and across ecosystems. Red List assessments help identify species and places that conservation action may prioritize.
International Union for Conservation of Nature: An international organization whose members include governments and civil-society organizations, working on nature conservation and sustainable use. IUCN maintains the Red List and coordinates its assessment framework.
Extinction crisis: The rapid, human-driven increase in species extinctions and extinction risk across the world. The Red List documents the scale and distribution of assessed species’ risks.
IUCN Red List Criteria: Five quantitative criteria for assessing extinction risk, based on factors such as population decline and restricted range. Assessors apply these criteria to decide which category fits a species.
Subpopulation: A geographically or otherwise distinct group within a population, with little demographic or genetic exchange with other groups. Some assessments consider risks to subpopulations as evidence about the whole species.
Key Biodiversity Areas: Sites that contribute significantly to the global persistence of biodiversity, identified using standardized criteria. Threatened species assessments can help identify sites meeting these criteria.
IUCN Species Survival Commission: A network of experts within IUCN that contributes scientific knowledge to species conservation. Its specialist groups and partners conduct and support many species assessments.
Red List Index: An indicator of changes in overall extinction risk for groups of species, derived from changes in Red List categories. It aggregates repeated assessments to track biodiversity trends over time.