Explainer: Time to extinction

Abstract

Time to extinction (TTE) is an estimate of how long a population, species or wider biological group persists before reaching a stated endpoint, such as extinction, local loss or a defined level of severe decline. The estimate depends on where the clock starts, what endpoint stops it, what evidence is available and how uncertainty is handled. In conservation biology, TTE is usually estimated by projecting possible population futures under specified threats and management choices. In historical and fossil records, TTE is inferred backwards from incomplete evidence such as sightings, specimens, fossils, dated remains, environmental DNA and non-detections. TTE complements extinction probability by showing how quickly loss is expected or inferred to occur, not just whether it occurs within a chosen period. The concept is useful for comparing collapse rates, intervention windows, extinction debts and uncertainty, provided each estimate states the biological entity, spatial scale, start point, endpoint, evidence base, assumptions and uncertainty.