Invasive species, also called introduced species, alien species, or exotic species, are any nonnative species that significantly modifies or disrupts the ecosystems it colonizes. Such species may arrive in new areas through natural migration, but they are often introduced by the activities of other species. Human activities, such as those involved in global commerce and the pet trade, are considered to be the most common ways invasive plants, animals, microbes, and other organisms are transported to new habitats.