Extinction risk

Extinction risk is the likelihood that a species will disappear from the wild or become extinct. It reflects threats, population condition, and the species’ vulnerability to change.

Population viability analysis: A quantitative method that estimates a population’s probability of extinction under specified conditions. It translates population data and threats into estimates of extinction probability.
IUCN Red List: A global system for assessing species’ extinction risk and documenting their conservation status. Its categories communicate assessed risk using standardized criteria.
Population size: The number of individuals in a population at a given time. Small or rapidly shrinking populations can meet risk thresholds more readily.
Biodiversity loss: The decline or disappearance of biological diversity at genetic, species, or ecosystem levels. Rising extinction risk is one pathway through which biodiversity is lost.
Extinction probability: The probability that a population or species becomes extinct within a specified time and scenario. It is the central quantity behind many estimates of extinction risk.
Minimum viable population: The smallest population estimated to have a specified probability of persistence over a stated period. Small populations are more exposed to chance events that can increase risk.
IUCN Red List categories: The status categories used by the IUCN to classify assessed species, from Least Concern to Extinct. The categories turn assessments into comparable statements of risk.
Population trend: The direction and rate of change in a population’s size over time. Decline over time is direct evidence used in many risk assessments.
Endangered species: Species facing a very high risk of extinction in the wild under a defined classification system. This status identifies a high-risk subset of species needing focused conservation.
Extinction risk assessment uncertainty: Uncertainty in estimates of extinction risk arising from limited data, model assumptions, and future conditions. Assessments can differ when evidence is sparse or plausible futures are hard to predict.

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