Species extinction

Species extinction is the permanent loss of a species when its last surviving individual dies. It differs from local extinction, which leaves the species alive elsewhere.

Extinction vortex: A self-reinforcing decline in which small populations lose genetic diversity and become increasingly vulnerable to further decline. Small populations can enter this feedback loop as extinction risk rises.
Dodo: An extinct flightless bird native to Mauritius, last recorded in the late seventeenth century. Its disappearance followed human arrival, hunting, and introduced animals on an isolated island.
IUCN Red List: A global assessment system that classifies species by their risk of extinction. It distinguishes species already extinct from those facing varying levels of risk.
Ecological extinction: The disappearance of a species' ecological role despite the survival of some individuals. A species can cease functioning in an ecosystem before its final individual dies.
Sixth mass extinction: The proposed current episode of unusually elevated extinction rates driven largely by human activities. Whether current losses constitute a mass extinction depends on rates, comparisons, and future trajectories.
Allee effect: A reduction in individual survival or reproduction when population density becomes too low. Sparse populations may struggle to find mates or cooperate, accelerating decline.
Passenger pigeon: A North American pigeon once numbering in billions that became extinct in 1914. Commercial hunting and habitat change drove an exceptionally abundant species to extinction.
Extinction risk: The probability that a species will become extinct within a stated time frame. Risk estimates help direct monitoring and conservation resources before a species disappears.
Extirpation: The disappearance of a species from a particular region while it survives elsewhere. It clarifies the geographic limit of extinction, which concerns global loss.
Background extinction rate: The long-term rate at which species disappear outside mass-extinction events. It provides the baseline for judging how unusual modern extinction rates are.

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