Economic Dimensions of the Problem of Invasive

tacks, and the establishment of the Office of Homeland Se-curity, many individuals have become aware of the threat of biological weapons directed towards people. However, few realize how vulnerable the U.S. agricultural infrastructure is to pests and disease outbreaks resulting from accidental or deliberate introductions of invasive species. Over the past 200 years or so, more than 50,000 foreign plant and animal species have become established in the United States. About one in seven has become invasive, with damage and control costs estimated at more than $138 billion each year (USDA/APHIS, 2001). An “invasive species ” is defined as a species that is non-native (or alien) to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm or harm to human health. (Exec. Order No. 13112, 1999). Invasive species ca