Invasive Species

Invasive species, also called invasive exotics or simply exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions.

• The first definition, the most used, applies to introduced species (also called "non-indigenous" or "non-native") that adversely affect the habitats and bioregions they invade economically, environmentally, and/or ecologically. Such invasive species may be either plants or animals and may disrupt by dominating a region, wilderness areas, particular habitats, or wildland-urban interface land from loss of natural controls (such as predators or herbivores). This includes non-native invasive plant species labeled as exotic pest plants and invasive exotics growing in native plant communities. It has been used in this sense by government organizations as well as conservation groups such as the International Union for Conservation of Nature (IUCN) and the California Native Plant Society. The European Union defines "Invasive Alien Species" as those that are, firstly, outside their natural distribution area, and secondly, threaten biological diversity. It is also used by land managers, botanists, researchers, horticulturalists, conservationists, and the public for noxious weeds. The kudzu vine (Pueraria lobata), Andean Pampas grass (Cortaderia jubata), and yellow starthistle (Centaurea solstitialis) are examples.

• The second definition includes the first, but broadens the boundaries to include indigenous or native species, with the non-native ones, that disrupt by a dominant colonization of a particular habitat or wildlands area from loss of natural controls (i.e.: predators or herbivores). Deer are an example, considered to be overpopulating their native zones and adjacent suburban gardens, by some in the Northeastern and Pacific Coast regions of the United States.

• The third definition identifies invasive species as a widespread nonindigenous species. This one can be too broad, as not every nonindigenous or "introduced" species has an adverse effect on a nonindigenous environment. A nonadverse example is the common goldfish (Carassius auratus), though common outside its native range globally, it is rarely in harmful densities to a native habitat.

Because of the variability of its definition, and because definitions are often from a socioeconomic perspective, the phrase invasive species is often criticized as an imprecise term for the scientific field of ecology. This article concerns the first two definitions; for the third, see Introduced species.