Coordination and collaboration has been building in the National Park Service (NPS) and the federal government to meet the issue of invasive species head on. But managing invasive species is a complex issue due to regional differences in species, adapting strategies to fit different ecosystems, and raising awareness about the harm they can cause. Explore this page to learn more about what an invasive species is.

Definitions to Know

  • Invasive species: With regard to a particular ecosystem, a non-native organism whose introduction causes or is likely to cause economic or environmental harm, or harm to human, animal, or plant health (Executive Order 13751).
  • Non-native species: Species that occupy or could occupy park lands directly or indirectly as the result of deliberate or accidental human activities (NPS Management Policies 2006).
  • Native species: All species that have occurred, now occur, or may occur as a result of natural processes on lands designated as units of the national park system (NPS Management Policies 2006).
  • Alien species: Informal term for non-native species and its use by NPS is discouraged. However, the term is still commonly used by the international community, such as the International Union for Conservation of Nature.
  • Exotic species: Informal term for non-native species. Use by NPS is also discouraged and is being phased out.
  • Feral species: Primarily refer to non-native animals that have escaped from captivity or domestication and reverted to a wild state.
  • Aquatic:Of, relating, or pertaining to water
  • Terrestrial: Of, pertaining to, or corresponding to land (on Earth), as opposed to water and air

It is often thought that the terms 'invasive' and 'non-native' can be used interchangeably, but this is not always true. Learn more about the correct term usage and the differences between invasive species and non-native species on the What You Can Do page .

Spread of Invasive Species

The ideal way to address invasive species is to keep them from establishing in a new area in the first place. To do that, national park managers need to know how invasive species arrive in a new ecosystem, or the "pathway" through which the species came. Unfortunately, any person, pet, vehicle or piece of wood coming in and out of a park is a potential pathway for invading species. Each park faces unique challenges in preventing the introduction and spread of invasive species.

Some examples of common pathways include:

  • Transportation of people or goods

  • Plant and pet trades

  • Ecosystem disturbances

Additional Invasive Species Facts

  • Invasive species thrive because they outcompete native species.

  • Invasive species often destroy habitat, affecting the places where other plants and animals naturally live.
  • The NPS also manage invasive diseases in national parks.
  • Many invasive species are introduced through the movement of humans, either intentionally (e.g., through the release of an unwanted pet into the wild) or unintentionally (e.g., through the soles of shoes). Learn how to fight the spread on the Prevention page under What You Can Do.

Although there is some overlap, invasive species are generally put into three groups: terrestrial plants, terrestrial animals, and aquatic species. Learn more below.

Photo credits (left to right): lionfish credit to NPS, Tree of Heaven photo credit to Richard Gardner, UMES, Bugwood.org, feral swine photo credit to Missouri Department of Conservation

Last updated: February 19, 2019