Feral

A feral organism is one that has changed from being domesticated to being wild or untamed. In the case of plants it is a movement from cultivated to uncultivated or controlled to volunteer.

As with any introduced species, the introduction of feral animals or plants to non-native regions may disrupt ecosystems and has, in some cases, contributed to extinction of indigenous species. Feral species may however eliminate "problem" species such as rodents, harmful insects, or aggressive plants. Likewise returning lost species to their environment can have beneficial effects, such as bringing damaged ecosystems back into balance.