About Invasive Species

Updated May 28, 2026

Key Points

Invasive species cause harm to our environment, economy and health.
Common invasive species include mosquitoes, mice and rats.
The U.S. Fish and Wildlife Service has undertaken a number of projects to help combat invasive species
Learn about projects, laws and regulations, and how you can help.

Dangers of Invasive Species

Invasive species cause tremendous harm to our environment, economy and health. When invasive species eat or crowd out native species, they reduce the vital biological variety we call biodiversity. Ecosystems with low biodiversity are more vulnerable to disease and other environmental stresses.

At worst, invasive species can lead to the extinction of native species. Invasive species also can spread disease and inflict costly damage on infrastructure, such as roads, canals and levees.

The origin and effects of invasive species vary. Many invasive species are spread or introduced accidentally, on the hulls of boats or soles of shoes, for example. Some are purposely acquired pets or garden trees or flowers that end up in the wild. Invasive fish and wildlife can prey on native animals and outcompete them for food and habitat. Invasive plants can outcompete native vegetation for space, moisture, sunlight and soil nutrients.

Although invasive species occur on all continents, islands experience disproportionate impacts. Islands make up just 5.3% of Earth’s land area, but they are biodiversity hot spots — home to a host of species. Unfortunately, islands also see the greatest concentration of species extinctions. About 75% of all reptile, bird, amphibian and mammal extinctions have occurred on islands. Invasive species have played a role in most of them.

An offshore view of coral waters and in the distance a lush, green, tropical island — Islands such as Palmyra Atoll National Wildlife Refuge in the Pacific Ocean are disproportionately affected by invasive species.

Common Invasive Species

The head of a bright red bird with a black beak and eyes, with a mosquito perched near its eye — Mosquito-borne diseases have played a hand in the extinction and decline of many native Hawaiian forest birds, including the ‘apapane, shown here with a mosquito near its eye.

Many non-native mosquitoes found in the U.S. harm native wildlife and humans. For example, the southern house mosquito — inadvertently introduced to Hawaii — is now the primary spreader of avian malaria and avian pox.

A black-colored wild pig standing amid dense, green vegetation — Feral swine — escaped domestic pigs, Eurasian wild boars and hybrids of the two — are extremely destructive.

In the U.S., feral swine number more than 6 million and are found in at least 38 states or territories. Feral swine root up, trample and eat cropland and property, including cultural and historic resources. They prey on ground nesting birds, amphibians, reptiles and other wildlife. They can carry at least 30 viral and bacterial diseases

Management and Conservation Projects

The U.S. Fish and Wildlife Service works to prevent, control and eradicate invasive species, using environmentally sensitive approaches. Here are a few major projects:

In 2019, we provided 2,350 invasive species prevention signs for boat ramps and trailheads on wildlife refuges, hatcheries and Service administrative sites. The signs alert the public about invasive species and how to prevent their spread.
From 2019 to 2021, we increased the number of invasive species strike teams that work on national wildlife refuge lands and waters from five to 14. These teams carry out invasive species prevention, early detection and rapid-response activities.

Eight large white-and-black-colored birds with light blue bills perched on tropical vegetation — Red-footed boobies at Palmyra Atoll National Wildlife Refuge.

We eradicated invasive black rats in 2012 from Palmyra Atoll National Wildlife Refuge in the Pacific. The rats were devastating native plants, seabirds and invertebrates. Since the eradication, population sizes and reproductive success have increased for native tree species, seabirds and crabs. The entire population of the invasive tiger mosquito, which relied on rats for its blood meals, has disappeared. Increases in seabird numbers have meant increases in guano production, which translates into greater nutrients for the coral reef system.
We are in the process of confirming a successful eradication of nutria at Maryland’s Blackwater National Wildlife Refuge and Chesapeake Bay. Nutria were devouring the roots of native marsh plants that keep the marsh healthy and intact. The marsh is slowly recovering. The nutria eradication benefits all plants and animals that use marsh habitat, and protects shorelines from sea-level rise and storms.
We eradicated yellow crazy ants at Johnston Atoll National Wildlife Refuge in the Pacific. The ants were spraying formic acid, causing injury and death to nesting seabirds, and reducing available nesting seabird habitat. Seabird survival and nesting is now increasing.
We removed invasive feral horses and burros at Nevada’s Sheldon National Wildlife Refuge. The removal has led to the recovery of thousands of acres of upland and streamside habitat, improving water quality and quantity in desert springs, and benefiting sage grouse, threatened Lahontan cutthroat trout and other fish and wildlife.
We eradicated invasive black rats at Desecheo National Wildlife Refuge in Puerto Rico. The rats were devastating native species and the ecosystem. Many native species are now recovering, including the Desecheo dwarf gecko, the slippery backed mabuya, the Puerto Rican racer and the threatened cactus, higo chumbo.

Two men remove Verbesina, an invasive plant with yellow flowers, from a field dotted with large grayish-colored birds — Volunteers remove invasive Verbesina encelioides (golden crownbeard) plants at Midway Atoll National Wildlife Refuge in the Pacific.

We have eradicated 99% of invasive Verbesina encelioides (golden crownbeard) plants at Midway Atoll National Wildlife Refuge in the Pacific. This has benefited the largest nesting colonies of Laysan and black-footed albatrosses on the planet, as well as endangered short-tailed albatrosses, Laysan ducks and many other seabirds and native plants.
In 2023, we will begin a project to eradicate 99% of invasive carp at North Carolina’s Mattamuskeet National Wildlife Refuge. The effort will help restore the native submerged aquatic vegetation that provides food for the lake’s fish, waterfowl and other native wildlife.
Partnerships are critical in our work, allowing us to leverage resources and work more strategically. In 2015, we developed an Island Restoration Memorandum of Understanding to work to eradicate invasive species from islands and restore them. Partners include Island Conservation, the Department of Agriculture’s Animal and Plant Health Inspection Service Wildlife Services program, American Bird Conservancy, The Nature Conservancy and the National Park Service. In 2020, we established the National Invasive Species Prevention Memorandum of Understanding with the North American Invasive Species Management Association, Wildlife Forever and the National Park Service to prevent the introduction and spread of invasive species onto federal lands and waters and beyond.

Three field crew members in waders holding up European green crabs. Marsh, trees, and overcast sky in background.

How You Can Help

Learn to Fight Invasive Species

These are among the laws and regulations that guide invasive species work for the Service:

National Invasive Species Act of 1996

Contact Us

If you have questions or would like to report an invasive species, please reach out to any of the contacts listed below based on their roles. These individuals coordinate across the nation and as necessary may direct your inquiry to the appropriate local Service staff, or to a relevant federal, state, or tribal agency, to ensure a timely and effective response. Thank you for your interest in invasive species!

Aaron Martin, National Invasive Species Coordinator, aaron_e_martin@fws.gov, 907-786-3510 | Areas of expertise: terrestrial and aquatic invasive plants and animals, prevention and education, early detection, rapid response, eradication, and long-term management.

Kristen Sommers, Injurious Species Listing Coordinator, kristen_sommers@fws.gov, 571-329 -2214 | Areas of expertise: aquatic invasive species policy and management, and the Injurious Wildlife Program

McKayla Spencer, Interjurisdictional Invasive Species Rapid Response Team Coordinator, mckayla_spencer@fws.gov, 352-756-6808 | Areas of expertise: early detection, rapid response, invasive species response procedures, terrestrial and aquatic invasive plants and animals, eradication, and long-term management.

Jolene Trujillo, National Integrated Pest Management Coordinator, jolene_trujillo@fws.gov, 703-859-1626 | Areas of expertise: pesticides, biocontrol, pest management, aquatic and terrestrial invasive species

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