Invasive species / Invasive alien species

Species whose introduction and/or spread by human action outside their natural distribution threatens biological diversity, food security, and human health and well-being. ‘Alien’ refers to the species’ having been introduced outside its natural distribution (‘exotic’, ‘non-native’ and ‘non-indigenous’ are synonyms for ‘alien’). ‘Invasive’ means ‘tending to expand into and modify ecosystems to which it has been introduced’. Thus, a species may be alien without being invasive, or, in the case of a species native to a region, it may increase and become invasive, without actually being an alien species.