Invasive Species Definitions

Invasive Species Terminology and Definitions

To standardize invasive species terminology, FISC has adopted the following definitions as described in the publication “Invasive Species Terminology: Standardizing for Stakeholder Education” from the Journal of Extension (Iannone et al. 2020). You can read this publication here


Standardized Terminology

Native: A species that occurs naturally in a specified geographic area.

Nonnative: A species that does not occur naturally in a specified geographic area.

Introduced: A species brought to a new geographic area intentionally or unintentionally by humans.

Established: A species having a self-sustaining and reproducing population in a specified geographic area without the need for human intervention. Applies to both native and nonnative species.

Invasive: A species that (a) is nonnative to a specified geographic area, (b) was introduced by humans (intentionally or unintentionally), and (c) does or can cause environmental or economic harm or harm to humans.

Nuisance: An individual or group of individuals of a species that causes management issues or property damage, presents a threat to public safety, or is an annoyance. Can apply to both native and nonnative species.

Range change: The circumstance of a species’ current/existing range growing, shrinking, or shifting over time. This change can happen to native and nonnative species with or without human assistance.


Terminology That Should Be Avoided and Why

Native invasive: Often used to describe individuals or a group of individuals of a native species in a context in which they are a nuisance. It creates confusion, as invasive species by definition are nonnative. In addition, the term confounds two separate issues—biological invasions caused by humans moving species over vast distances and a native species that causes management issues.

Invasive exotic: Often used to describe a nonnative species that causes environmental and/or economic harm or harm to humans (i.e., a species that is invasive). It is redundant and confusing. An invasive species by definition is exotic, but not all exotic species are invasive, and the term exotic has other potential interpretations (see appendix).

Invasive weed: Used to describe an invasive plant. It is easier to say an invasive plant. In addition, weed is a cultural term describing a plant (native or nonnative) not wanted in a given situation (e.g., agriculture, home garden, etc.). For this reason, the term may lead people to believe incorrectly that all weeds are invasive.

Alien/foreign/nonindigenous: All three terms are synonymous with nonnative. They evoke political ideals unrelated to invasive species. In addition, based on one’s political beliefs, the terms may have negative connotations, despite most nonnative species not causing harm.


Legal Terminology

Noxious weed: Any plant or plant product that can directly or indirectly injure or cause damage to crops (including nursery stock or plant products), livestock, poultry, or other interests of agriculture, irrigation, navigation, the natural resources of the United States, the public health, or the environment. [Agricultural Risk Protection Act, Public Law No.106-224 (2000,p. 114)]

Injurious: Inflicting or tending to inflict injury. [Merriam-Webster (n.d.)]

Prohibited: A species determined injurious to humans or human interests (e.g., agriculture, forestry, horticulture, or wildlife management). [Lacey Act (1900)]

Conditional/restricted: A species that can be possessed or imported for research, public exhibition, or commercial use in controlled settings that limit the possibility of escape. Possession requires appropriate permits. Species cannot be owned as pets.


Additional Invasive Species Terminology

Adventive: A nonnative species that has established in an area, but whose mode of arrival to that area is unknown. That is, it may or may not have been caused by human introduction.

Aggressive: This term means different things for different organisms. For animals, an aggressive species would mean the species is likely to attack when confronted or encountered. For plants, an aggressive species is one that can overtake and dominate the area where it grows. This term can be applied to both native and nonnative species.

Competitive: A species that is good at acquiring resources relative to other species. This ability can lead to the depletion of resources for other species. This term can be applied to both native and nonnative species.

Cultivated: A species (typically a plant) that is grown and maintained by humans.

Endemic: A species that occurs only in a given area—for example, the species is endemic to dunes in southern Florida.

Escaped: A species that now exists outside of cultivation, production, or domestication regardless of the mechanism by which this release occurred.

Exotic: This term is synonymous with nonnative. However, nonnative is a better term for education, as exotic, particularly in the pet trade and ornamental houseplant trade, can be perceived as fancy or unique rather than nonnative.

Feral: A species (typically animal) that has escaped from domestication and now occurs wild. Indigenous – This term is synonymous with native. Native is preferred as this term, like foreign, alien, or nonindigenous, may be perceived in political rather than biological or ecological contexts.

Native range: This term refers to the geographic area from which a nonnative species originated (prior to humans moving the species around the globe) as well as the geographic area over which a native species is found.

Naturalized: This term is synonymous with the term established. A nonnative species that has now established and maintains a reproducing population with no assistance from humans. Naturalized is less favorable for education than established due to the word natural being nested within it. This inclusion of natural is reported by multiple Extension professionals to cause stakeholders to believe the species to be good or part of the natural ecosystem.

Pest: A species (typically animal) that is not wanted in a given area due to negative economic and/or environmental impacts. This term can be applied to both native and nonnative species.

Weed: A plant species not wanted in a given area because it has negative economic and/or environmental impacts. This term is also used to describe a species that largely occurs in disturbed areas or is unwanted in home gardens. This term can be applied to both native and nonnative species.