Invasive species are non-native species of animals, plants, microorganisms, or pathogens that take over the habitat of other species, forcing the native species to decline in population or to disappear from their natural environment. Invasive species tend to be highly competitive, highly adaptive, and successful at reproducing.
Bullfrogs compete with and prey on a wide range of native species and have been blamed for native species declines in Washington.
Butterfly bush is a popular ornamental shrub that forms dense thickets, especially along river banks and river gravel bars, which then crowd out native vegetation.
Dense stands of common crupina can out-compete native plant species, can increase the risk of soil erosion, and are not palatable to livestock.
Dalmatian toadflax outcompetes desirable species in pastures, rangelands, and natural areas.
This invasive species competes strongly with Dungeness crab. It is an efficient forager and preys on clams, oysters, mussels, and small crustaceans.
Exotic leafrollers are pests of fruit trees and ornamentals. They damage trees by rolling and eating leaves, conifer needles, and shrubs.
Garlic mustard is shade tolerant and out-competes native plants, changing the structure of plant communities on the forest floor and diminishing food sources for certain wildlife.
The gypsy moth devours the leaves of more than 500 different species of trees and shrubs and causes enormous damage to the environment and the economy.
Himalayan blackberry can grow in a variety of environments and shades out smaller native species, reducing native plant and wildlife diversity.
Japanese knotweed, an escaped ornamental, is a shrubby perennial that grows aggressively along roadways, neglected gardens, streambeds, and in moist, wet places.
Kudzu is a perennial, trailing vine that can grow up to 1 foot a day and as long as 98 feet. A single root crown may produce as many as 30 vines, which expand out in all directions.
Marine clams grow prolifically forming dense quantities that displace other native species. These clams have displaced native clams from their former ranges.
Mitten crabs spend most of their lives in freshwater and can prey on and compete with many native aquatic species, posing a threat to ecosystems and fisheries.
Nutria live in freshwater environments and feed primarily on the roots and stems of wetland plants, consuming about 25 percent of their body weight every day.
Parrotfeather rapidly takes over shallow lakes, ponds, and ditches by forming dense mats of vegetation that can entirely cover the water surface, crowding out native biodiversity.
Quagga and zebra mussels are freshwater mollusks that colonize lakes and rivers, and clog water intake pipes and filters.
Scotch broom is an upright shrub in the pea family, and grows primarily in open, dry meadows and along roads. It crowds out native species and negatively impacts wildlife habitat.
Spartina species are aquatic grasses that grow in cirucular clumps on mud flats and marshes, outcompeting native plants.
Saltcedar's deep root system and large water demands can significantly lower groundwater tables and increase surface soil salinity, stressing many native plants.
Tunicates can smother other sea life such as clams, mussels, and oysters, and nothing eats them because they are toxic to other species.
VHS is a deadly fish virus and aquatic invasive species that attacks and weakens the blood vessels of fish, and afflicts more than 50 species of freshwater and marine fish.
Asian carp are found in both flowing and still water, and consume large amounts of vegetation and plankton, affecting food webs and system ecology.
Brazilian elodea is a robust, freshwater plant originally sold in Washington pet stores for aquariums.
Common reed is a large grass or reed with creeping rhizomes. It forms dense stands, typically in or near wetlands.
Eurasian milfoil forms dense mats that shade out native aquatic plants, inhibit water flow, and hamper recreational activities.
Exotic apple fruit pests can damage trees and shrubs, with impacts depending on the species. They pose a serious threat to our state fruit crops and commercial fruit industries.
Giant hogweed is a biennial plant that grows up to 20 feet tall and invades disturbed areas across the Pacific Northwest and northeast United States.
Hawkweeds are perennial herbs that produce large quantities of seeds and can hybridize with many other plant species, making them aggressive competitors.
Hydrilla is a tenacious weed that has several ways to propagate. It is considered one of the worst aquatic weeds in the country.
Kochia is a drought-tolerant plant with a deep root, and outcompetes crops such as potatoes, alfafa, and wheat, and may be poisonous if eaten.
Leafy spurge can survive in a variety of conditions and is toxic to some animals and unpalatable to most, and can cause blisters on humans.
The Mediterranean snail is small (less than
1 inch across) and can survive long periods of hot and dry weather without food. They can clog harvesting machinery, and contaminate crops.
Northern snakehead fish are voracious eaters that prey on fish, crustaceans, frogs, insects, small reptiles, birds, and mammals, with significant impacts to native species.
New Zealand mud snails are tiny (less than 6 mm) aquatic snails that can dominate river and lakebed habitat by achieving densities of more than 100,000 per square meter.
Purple loosestrife invades wetlands and quickly overtakes other species, such as cattail, that provide better food and nesting habitat for birds, bog turtles, mink, and muskrat.
Crayfish are easily introduced into areas where they are not native, sometimes with disastrous results to the ecosystem and native species.
Scotch thistle invades disturbed areas, and its dense stands compete with native plants for resources, and can form a physical barrier to water and grazing for animals.
Knapweeds can impair wildlife habitat, decrease plant diversity, and increase soil erosion. They also can cause crop losses and reduce forage, and pose wildlife hazards.
Tansy ragwort is a biennial herb that can cause severe economic impacts and is one of the most common causes of poisoning in cattle and horses.
This rooted, perennial, aquatic plant is found in freshwater lakes and ponds, and reduces habitat quality for fish, waterfowl, and other wildlife.
Water chestnut is an aquatic, floating plant that grows in dense, floating mats that restrict light, reduce oxygen, and displace other vegetation.