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Effects of Exotic Species on Forest Wildlife and Wildlife Habitat

Exotic nonnative plants and animals were introduced into this country either intentionally or accidentally. In addition, many native species have been accidentally or intentionally introduced to other regions of the country, sometimes with negative consequences. The latter group will not be discussed in this chapter. Since European colonization, thousands of plants and animals have been intentionally introduced into the United States. Many of these introductions have been beneficial to humans. Nonindigenous crops and livestock are the foundation of U.S. agriculture (U.S. Congress, Office of Technology Assessment 1993). Other exotic species are mainstays of horticulture and the pet and aquarium industries; others are used successfully for soil erosion control and biological control. Of the introduced species, only a relatively few cause great harm. The U.S. Congress, Office of Technology Assessment, estimates 4 to 19 percent of exotic species fall into this category. Another 6 to 53 percent are estimated to have neutral or unknown effects. Many of our most invasive exotic species have been introduced into an environment in which they did not evolve and in some cases they have few or no natural enemies. Once established, they reproduce and spread unimpeded by (and often at the expense of) native plants and animals.