The U.S. Army Corps of Engineers (Corps) is responsible for the environmental stewardship of 456 water resources development projects located in 43 states occupying 5,500,000 surface acres, 237 navigation locks, 926 harbors, 75 hydropower projects, and 25,000 miles of inland and coastal waterways. Invasive species occur at most of these projects and include terrestrial and aquatic plants, animals, and insects. Invasive species are serious threats impacting wildlife and fisheries habitat as well as human health, and impose enormous costs for eradication and management efforts.
Invasive species have been introduced through routes called invasion "pathways." Transported by air, water, rail, or road, invasive species move beyond natural geographic barriers and inhabit new sites. By altering species diversity, hydrology, nutrient cycling, and other ecosystem processes, invasive species can change whole ecosystems and irreparably damage natural resources. The management of invasive species requires that resource managers take steps in the war against them. These include: 1) prevention, 2) early detection and rapid response, 3) eradication, and 4) control.
Education is an important mechanism to prevent the introduction of invasive species. Recreational boaters introduce invasive species by, for example, transporting vegetation on trailers and by the release of live bait in bodies of water. Ornamental plants and pets may be imported from a different country to provide unusual products to the market. Some non-native species, intentionally introduced for beneficial purposes, later turn out to be invasive. A small percentage cause serious problems in their new environments and are collectively known as "invasive species." Most U.S. food crops and domesticated animals are non-native species and their beneficial value is obvious - for example, managed livestock consist of non-native species that are not invasive.
The management of invasive species requires that resource managers be properly trained in the identification of invasive species and methods available for control. Aquatic vegetation problems can be addressed through biological, chemical, and mechanical control. Invasive terrestrial species must be dealt with on a case-by-case basis. Resource managers must know how to respond when an invasive species is detected.
The eradication of an invasive species may be an option if the organism is rapidly detected and the extent of its invasion is established. Many invasive species have already been established and control is the only option. The cost of control can often be excessive and priority must be given to efficiently using the resources available.