Invasive Species

According to Presidential Executive Order 13112, an "invasive species" is defined as a species: 1) that is nonnative to the ecosystem under consideration, and 2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health.

Nonnative species become invasive in a new environment when the natural predators, diseases, or other biological mechanisms that kept the species in check within its former habitat are missing in its new environment. Lacking this biological balance, the invading species effectively changes the biodiversity of a locale. This can often cause millions of dollars in damage to local economies.

play audio
Invasive Species PSA
By Kenai Watershed Forum

Scope & Effect

Approximately 50,000 nonnative species have been introduced to the United States as a result of human movements, commerce, and trade. Livestock, pets, food crops, and ornamental plants are examples of species that have been intentionally introduced to the benefit of society. Although many new species are unintentionally introduced to new environments each year, many cannot survive outside their native habitat. Other species thrive, yet have no known adverse effects to the ecosystem into which they are introduced.

Of the remaining introduced species that find the new ecosystem supportive, those that contribute negative effects on the ecosystem or adverse impacts to the economy or human health are labeled invasives. Invasive species can change ecosystems by altering habitat composition, increasing wildfire risk, competing with native species for food and territory, changing existing predator/prey relationships, reducing productivity, or otherwise disrupting natural habitat functions. In doing so, invasive species pose one of the greatest threats to biological diversity.

Aquatic Nuisance Species Management Plan

In 2002, the Department of Fish and Game prepared a management plan to address the threat invasive species pose to the aquatic ecosystems of the state. The Alaska Aquatic Nuisance Species Management Plan (PDF 1,210 kB) was approved by the federal Aquatic Nuisance Species Task Force (ANSTF). Under Section 1204 of the Aquatic Nuisance Species Prevention and Control Act the ANSTF has provided limited funding to state’s with an approved plan.

The ANS management plan describes

  • Alaska’s history of invasion,
  • species considered to be the highest threat,
  • pathways for introduction
  • management actions to
    • prevent the introduction or spread of invasive species,
    • promote early detection and rapid response actions, and
    • control or eradicate invasive species.


The Department of Fish and Game (ADF&G) is responsible for management of fisheries, wildlife and habitats. ADF&G strives to protect native fish and wildlife and the habitats that support them from impacts imposed by invasive species. The Department of Natural Resources (DNR) has management responsibility for terrestrial and freshwater plants. As appropriate, the two agencies collaborate to safeguard Alaska ecosystems from aquatic invasive species. If you are seeking information about aquatic invasive plants, such as Elodea, please visit the DNR invasive plants website.