extinctions

Extinction is the permanent loss of a taxon, typically a species, when there are no living individuals capable of reproducing. Sometimes extinction is local, extirpation, while the lineage persists elsewhere; at other times it terminates an entire clade.

Most extinctions occur gradually through background extinction, driven by ecological and environmental change. Mass extinctions are events in which many taxa disappear in geologically short intervals, usually linked to rapid climate change, volcanism, ocean anoxia, asteroid impacts, or other upheavals.

The fossil record shows several mass extinctions; the largest was the Permian-Triassic event, followed by end-Triassic and Cretaceous-Paleogene. Since the origin of life, many other lineages have gone extinct; many species go extinct without being known to science.

Currently, human activities are accelerating extinction risk for many species through habitat loss, overexploitation, invasive species, pollution, and climate change. IUCN Red List assessments track extinction risk, and concepts such as extinction debt describe future losses due to past habitat degradation. Conservation aims to reduce drivers and preserve biodiversity and ecosystem services.