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Invasive Species

Male Mitten Crab/FWS

Invasive species, including both aquatic and terrestrial nuisance species, are defined as nonnative species that have caused or have the potential to cause significant economic or environmental harm or present a threat to human health. It is important to note that when we talk about a species being invasive, we are talking about environmental boundaries, not political ones.

Not all nonnative or nonindigenous species, however, are invasive species.  Many nonnative species provide important benefits and do not become invasive.  These include most U.S. food crops, and domesticated animals, and many of our pets and ornamental plants.  Introductions of invasive species have caused significant economic and ecological problems throughout North America.  Scientists, academics, leaders of industry, and land managers are realizing that invasive species are one of the most serious environmental threats of the 21st century.  Invasive species are considered the number two threat to native species, often contributing to Endangered Species Act listings, even promoting extinction of listed species.  Climate change will likely bring new invasive species management challenges to the Pacific Northwest.


  • Invasive Species Already Present in Washington

    In addition to the many invasive species from outside the U.S., there are many species from within the U.S. that are invasive in other parts of the country.

    Invasive species already present in Washington with the potential for serious ecological impacts include: Japanese and giant knotweed, parrot feather, barred owls, bullfrogs, European green crab, and cord grass (Spartina).  European green crab and cord grass (Spartina) also pose an economic threat to the Washington oyster industry, which contributes some $40-50M per year to the state’s economy. Invasive terrestrial plants, such as Scotch broom, Himalayan blackberry and various knotweeds, also threaten the integrity of native plant communities in Washington State. Potential explosive invasions in Washington State include zebra mussel and mitten crab introductions, which could be disastrous to shipping, irrigation, and hydroelectric facilities of the region, the effects on salmon are unknown. Invasive species introduced through ship ballast water exchange have the potential for serious ecological and financial damages.


    The U.S. Fish and Wildlife Service is the only agency of the U.S. Government whose primary responsibility is the conservation of the nation’s fish, wildlife, and plants. Because of our responsibilities, the Service is very concerned about the impacts that invasive species are having across the Nation. Invasive plants and animals have many impacts on fish and wildlife resources. Invasive species degrade, change or displace native habitats and compete with our native wildlife and are thus harmful to our fish, wildlife and plant resources.

    The Washington Fish and Wildlife Office provides invasive species coordination, technical support, and outreach to Federal, State, Tribal, and local governments in the Pacific Northwest through various activities and projects, including:

    Participation in the 100th Meridian Initiative, a national coordination, monitoring and outreach effort to prevent the westward spread of zebra mussels.

    Providing coordination and technical assistance to Service partners in the Pacific Northwest on nonindigenous species issues.

    Providing funding to the State of Washington for implementation of the State of Washington Aquatic Nuisance Species Management Plan.

    The Puget Sound Coastal and Partners for Fish and Wildlife Programs provide funding for a variety of invasive plant control projects ranging from Spartina to knotweed to Scotch broom. See Knotweed Control in King County for an example.

    Please report any invasive species sightings in Washington at the Washington Invasive Species Council website:

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