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Invasive Species
Africanized Honey Bees: 2003
Chinese Privet
Common Gorse
Leafy Spurge
Purple Loosestrife
Zebra Mussel Distribution
Map Layer
Plant Distribution - Chinese Privet
Plant Distribution - Chinese Tallow Tree
Plant Distribution - Common Gorse
Plant Distribution - Leafy Spurge
Plant Distribution - Purple Loosestrife
Zebra Mussel Distribution in North America
Dynamic Maps
Invasive Species - Zebra Mussels


  General Information About Invasive Species

downWhat are they?
downWhy are they a problem?
downWhat is being done about the problem?
downCommonly Used Terms
downRelated Links

  What are they?

Kudzu infestation
Kudzu infestation
James H. Miller, USDA Forest Service
Invasive species are defined as species that are non-native to the ecosystem under consideration and whose introduction causes or is likely to cause economic harm, environmental harm, or harm to human health. Invasive species can be plants, animals, or other organisms (e.g., microbes). Introductions of invasive species are primarily caused by human actions. While most invasive species were introduced to the United States, some are natives in one part of the country but serious pests in another part of the country. In addition there are problem plants that are native but invade managed habitats such as rangelands or agricultural fields.

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  Why are they a problem?

Variety of zebra mussels
J. E. Marsden,  Lake Michigan Biological Station
Invasive species threaten native plants, animals and ecosystems, as well as impacting agricultural ecosystems and other human activity. Control costs and environmental damages can add up to millions of dollars per year.

For example, Zebra mussels were introduced into the Great Lakes in 1988 and have since spread rapidly throughout the Great Lakes and other water systems in the United States. These mollusks compete with native species for food, damage structures and boats, and clog water intake pipes.

Man walking in a wetland infested with Purple Loosestrife
Purple Loosestrife (Lythrum salicaria) is a perennial wetland herb that has spread aggressively into wetlands in the northeast and the Midwest.
Eric Coombs, Oregon Department of Agriculture
Invasive plants such as Purple loosestrife also compete with native species. In the 1800's this wetland flower was introduced for ornamental and medicinal purposes, and it has since invaded wetlands across much of the nation. Purple loosestrife forms dense stands that replace native plants needed by wildlife for food and habitat.

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  What is being done about the problem?

Gypsy moth caterpillar  on a leave
Gypsy moth caterpillars are the number one forest and shade tree pest in the Northeast.
Scott Bauer, U.S. Department of Agriculture, Agricultural Research Service.
Many Federal agencies and private organizations work to prevent the introduction of invasive species, manage and contain those species that are already a problem, and educate the public about problem plants and animals. The Government's web site provides detailed information about Federal efforts concerning invasive species. Plants considered invasive species are identified and described in the USDA Natural Resources Conservation Service PLANTS database which includes information for plants in the United States and its territories.

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  Commonly Used Terms
  Ecosystem—A community of plants, animals and other organisms that are linked by energy and nutrient flows and that interact with each other and with the physical environment.

Introduced species—An organism that has been brought into an area where it does not normally occur. Most introductions are caused by human activity. Introduced species often compete with and cause problems for native species. An introduced species is not necessarily an invasive species. Also called exotic, non-native, or alien species.

Invasive species—A species that is non-native to the ecosystem under consideration and whose introduction causes or is likely to cause economic harm, environmental harm, or harm to human health. Invasive species tend to grow rapidly and spread easily, and frequently out-compete native species for space and resources. An invasive species may be introduced or may spread outside its normal range through natural processes.

Native species—A species that occurs naturally in an area (i.e. is not introduced.)

Northern snakehead with mouth open
Northern snakehead (Channa argus) are aggressive predators that feed opportunistically on amphibians, fish, aquatic birds, and, on occasion, small mammals. Of greater concern is the snakehead fish's ability to survive in waters with low dissolved oxygen and to travel across land
U.S. Geological Survey, Florida Integrated Science Center.
Non-indigenous species—With respect to a particular ecosystem, any species that is not naturally found in that ecosystem. Species introduced or spread from one region of the U.S. to another outside their normal range are non-indigenous, as are species introduced from other countries or continents.

Non-native species—See introduced species, invasive species, and non-indigenous species.

Noxious species—A plant species that is undesirable because it is troublesome and difficult to control. Not to be confused with species declared noxious by law (see noxious weed.)

Noxious weed—A plant defined by law as being especially undesirable, troublesome, and difficult to control.

Nuisance species—A species that threatens the diversity or abundance of native species or the ecological stability of an infested area, or that threatens commercial, agricultural, aquacultural or recreational activities dependent on such an area.

Species—A group of organisms that differ from all other groups of organisms and that are capable of breeding and producing fertile offspring. This is the smallest unit of classification for plants and animals.

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  Related Links, the gateway to Federal efforts concerning invasive species.




Animal and Plant Health Inspection Service, invasive species factsheet

Environmental And Economic Costs Associated With Non-Indigenous Species In The United States; David Pimentel, Lori Lach, Rodolfo Zuniga, and Doug Morrison; College of Agriculture and Life Sciences, Cornell University

Federal invasive species activities and programs: National Invasive Species Council

Nonindigenous Aquatic Nuisance Prevention and Control Act of 1990 (P.L. 101-646)

Northwest Fisheries Science Center Glossary of terms

USDA-NRCS Glossary of terms

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