Range Contraction

Range contraction is the shrinking of the geographic area occupied by a species. It is a sensitive indicator of population decline and is used as a criterion in IUCN Red List assessments (Criterion B: geographic range). Local extinction at the periphery of a range typically precedes total extinction. Anthropogenic drivers of range contraction include habitat destruction, water extraction (freshwater species), barriers to migration (dams), pollution, targeted overfishing, and climate change (thermal range shifts). Many fish species have contracted dramatically from their historical ranges, often without accurate baseline documentation of former distribution.

European sturgeon (Acipenser sturio) historically ranged from Norway to the Black Sea; today the last breeding population is restricted to the Gironde–Garonne–Dordogne river system in France — a range contraction of >95%.