Extirpation is also known as local extinction and refers to the situation when a species is no longer present in a specific geographical location. In contrast to extinction where a species does not exist anywhere, extirpation happens only locally and at least one population of the species is present somewhere else in the world.
Since the whole species doest not become extinct so it is quite possible for that population to be replaced by another population of the same species e.g., the reintroduction of the Canadian Gray wolves in areas where they have been extirpated. But the reintroduction/replacement can lead to reduced genetic diversity of the species.
Human activities, either directly or indirectly, are mainly responsible for extirpations. The direct impact is by hunting or trapping and the indirect impact is by habitat destruction through activities like polluting or damaging the resources or by introducing invasive species.
Extirpation can have a significant impact on the populations because if a predator is extirpated from an area, it can result in increased population sizes of some species in areas where resources are low.
Extirpation of Gray Wolves
Extirpation of the gray wolf (Canis lupus) is the common example of local extinction. Its extirpation was intentionally caused by humans from around one-third of its natural habitat range. The Gray wolves were largely distributed throughout Canada, North America, Europe and Asia. But due to conflict with humans for predation resources, they were naturally extirpated from a vast range of its natural habitat.
Later on, in the 1900s, the American Government declared them as vermin. So the humans targeted them and eventually cause their local extinction all of its natural habitat range except two states, Michigan and Minnesota. There was only a population of 300 gray wolves remaining in these areas.
But the impact of extirpation was not good as the populations of elk and other prey species became uncontrollable. The herbivores caused severe reduction of vegetation and other species depending on vegetation like beavers and bears were badly affected. The extirpation of gray wolves caused a trophic cascade.
In 1995, the authorities reintroduced the gray wolves in their natural habitat range so that the ecosystem returns to a more natural state. Despite the reintroduction, the species is still small in number and missing from most of its global habitat range.