Indicator Species

An indicator species is an organism whose condition signals the health of the ecosystem it inhabits. The spotted owl's decline indicates the degradation of old-growth forest, not because the owl is the forest's most important member but because the owl requires conditions only healthy old-growth provides. Monitor the owl and you monitor the forest. The canary's death indicates gas in the mine before the miner's metabolism registers it. The indicator species is valuable precisely because it is sensitive — it responds to changes in habitat condition before other members of the community do. Its sensitivity makes it the system's early warning.