Invasive Species: Background Information
Invasive species are plants, animals, fungi, or microorganisms that spread rapidly and cause harm to other species. Sometimes invasive species threaten entire ecosystems. Although some invasive species are native to North America, many are brought in from other continents. For example, purple loosestrife, a plant common in wetlands throughout the United States and Canada, was brought to North America from Europe in the 1800s - both accidentally and on purpose. Because it has no natural predators in North America, purple loosestrife is able to rapidly invade wetlands. Once established, purple loosestrife outcompetes and displaces many native species such as cattails. Because animals depend on native plants for food, nesting areas, and shelter, purple loosestrife invasions indirectly harm wildlife. Muskrats, bog turtles, and ducks are some of the species that suffer when purple loosestrife takes over.

Non-native species are brought into North America for a number of reasons. For example, 98% of the US food supply, including wheat, rice, domestic cattle, and poultry, comes from introduced plants and animals. However, one of the biggest ecological problems in North America is the introduction of non-native species that later become weeds or pests. About 10 percent of the non-native species introduced to North America are able to survive and become established. Of these, roughly one in every 10 species that becomes established in a new region becomes a serious pest. These non-native species invade gardens, agricultural fields, and natural areas such as wetlands, forests, and grasslands. They cause substantial harm to desirable plants, animals, and entire ecosystems, as well as economic losses estimated at billions of dollars per year.

For more information, visit our invasive species links.