Scientists, industry officials, and land managers are recognizing that invasive species are one of the most serious, yet least appreciated, environmental threats of the 21st century. Expanding global trade and travel with countries such as Russia, China, and South Africa have resulted in rapid increases in the rate of introduction and number of newly established invasive species in the United States. While most of the plants and animals that make their way here are benign or even beneficial (for example, cattle, wheat, and tulips are all non-native species), the small proportion that become highly invasive have had huge economic and biological impacts. Damages resulting from invasive species may include power outages; loss of farmland property values; increased operating costs; and loss of sport, game, or endangered species. While the damages caused by these species have been considerable, their precise economic impacts—particularly those that do not damage agriculture, industry, or human health—are not well documented. However, a recent study by Cornell University scientists estimated the total annual economic losses and associated control costs to be about $137 billion a year—more than double the annual economic damage caused by all natural disasters in the United States. Because invasive species encompass plants, animals, and microbes, the problems they cause vary. The following examples demonstrate some of their impacts: On rangelands, leafy spurge, an invasive plant from Eurasia, crowds out desirable and nutritious forage, reduces land values, and degrades wildlife habitat. Annual damages from this weed are estimated to exceed $100 million in the Great Plains states. In U.S. forests, 19 of the 70 major insect pests are invasive species. Also, over the past several years, over 6,700 trees were destroyed in New York and Chicago after the discovery of the Asian long-horned beetle, an insect that most likely arrived in packing material or wood from China. According to USDA’s Agricultural Research Service (ARS), if this beetle and other wood-boring pests become fully established in the United States, they could damage industries that generate combined annual revenues of $138 billion. In freshwater habitats, aquatic invasive species, such as the zebra mussel, clog lakes and waterways and adversely affect fisheries, public water supplies, irrigation, water treatment systems, and recreational activities. Great Lakes water users spend tens of millions of dollars annually to control zebra mussels. In saltwater habitats, the European green crab has been associated with the demise of the soft-shell clam industry in New England. The green crab has recently been introduced to the West Coast where there is serious concern that it could affect shellfish aquaculture and Dungeness crab populations. In 1996, the most recent estimate, researchers calculated that the potential economic damage to shellfish production there could be as high as $44 million a year. A threat to humans and animals, the West Nile virus, commonly found in Africa, West Asia, and the Middle East, is an invasive virus now present in 12 eastern states and the District of Columbia. Birds are the natural hosts for this microbe, which mosquitoes transmit from infected birds to humans and other animals. While the ecological impacts of invasive species can be devastating, they are hard to quantify. However, many scientists believe that invasive species are a significant threat to biodiversity—second only to habitat loss and degradation. Further, they are a major or contributing cause of declines for almost half the endangered species in the United States. On February 3, 1999, President Clinton issued Executive Order 13112 on invasive species. Among other things, the order requires federal agencies to (1) prevent the introduction of invasive species and (2) detect, respond rapidly to, and control them in a cost-effective, environmentally sound manner. The order established a National Invasive Species Council—chaired by the Secretaries of Agriculture, Commerce and the Interior—with members including the Departments of State, Treasury, Defense, and Transportation, and the Environmental Protection Agency. The order directs the Council to provide national leadership on invasive species and to see that federal agency efforts are coordinated and effective. The Secretary of the Interior was also directed to form an advisory committee (the Invasive Species Advisory Committee) to provide information and advice to the Council. The order emphasizes the need for federal and state cooperation, as the states have a key role in managing invasive species within their borders. For example, in fiscal year 2000, Florida—which has a strong invasive species program—spent over $127 million on invasive species activities. States also retain general control over state lands and determine how they will address invasive species on their lands. The order also states that the Council shall develop recommendations for international cooperation. An effort already underway before the Council was established is the joint U.S./Canadian effort to combat the sea lamprey—an eel-like ocean fish that fastens onto other fish and eats until sated. Since 1956, the two governments have worked jointly through the Great Lakes Fishery Commission to control the spread of this invasive aquatic, which has had a detrimental impact on the Great Lakes fishery. The Council was also directed to prepare a National Invasive Species Management Plan. The plan, issued in January 2001, provides a general blueprint for dealing with invasive species and contains 57 recommendations—3 of which focus on rapid response. The Council’s member agencies obligated about $631.5 million in fiscal year 2000 on invasive species-related activities; USDA provided almost 90 percent of this amount. USDA’s and particularly APHIS’ programs are significant in their breadth and scope. For example, APHIS has jurisdiction over plant pests, certain biological control organisms, the import and export of plant species, and animals and animal diseases considered harmful or a threat to livestock or poultry health. In addition, the Forest Service, which manages about 191 million acres of federal land, has authority for forest and rangeland pest and plant control. Interior provided the second largest amount of federal invasive species funding, $31.1 million in fiscal year 2000, or 5 percent of the federal invasive species funding. Interior agencies—such as the Fish and Wildlife Service, Bureau of Land Management, National Park Service, and Bureau of Reclamation—are involved in regulating the import of animals found injurious under the Lacey Act, enforcing laws and regulations governing the import and export of wildlife into the United States, implementing actions to address aquatic invasive species, and managing invasive species on various publicly owned lands. Defense provided the third largest amount of funding, about 2 percent. As the fifth largest federal land manager, Defense is responsible for controlling invasive species infestations on its installations and uses native plants to restore Defense lands. In addition, the Army Corps of Engineers spends several million dollars annually for controlling invasive aquatic plants and zebra mussels and for supporting research to develop control technologies for managing these invasive species. All told, at least 20 different federal agencies share responsibility and authority over some facet of invasive species management. In addition, several interagency groups help coordinate activities in this area. Executive Order 13112 directs the Council to work with the: Aquatic Nuisance Species Task Force, which coordinates activities relating to aquatic invasive species; Federal Interagency Committee on the Management of Noxious and Exotic Weeds, which coordinates weed management efforts primarily on federal lands; and Committee on Environment and Natural Resources of the National Science and Technology Council, which coordinates research efforts. Invasive species management covers such activities as prevention, detection, control, restoration, research and development, information management, and public education. Prevention—the exclusion of invasive species from the country or from specified regions or ecosystems—is the first line of defense. When this fails, successful management often hinges on early detection and rapid response to an invasion. Eradication or containment of invasive species is most efficient, and sometimes only possible, at an invasion’s earliest stages. Once an area becomes altered, control activities, which may be costly, are needed to restore the habitat. Invasive species that threaten agricultural crops or livestock are far more likely to elicit a rapid response than those affecting mainly natural areas. As shown in table 1, APHIS provided most federal rapid response funding—an estimated $125.8 million out of a total $148.7 million reported for fiscal year 2000. About 90 percent of APHIS’ funding was directed at invasive species that primarily threaten agricultural crops or livestock; another 9 percent was spent on the Asian long-horned beetle, which primarily threatens forestry. Interior, second among federal departments in total funding for invasive species, estimated that its agencies provided about $1.4 million for rapid response activities. Its rapid responses were directed at species that threaten natural areas. Many rapid response needs are not being met, according to agency officials and others, particularly for invasive species that threaten natural areas. When these needs are not met, the consequences—to the economy and the environment—can be costly. Invasive species that threaten crops or livestock are the most likely to be quickly addressed since APHIS, which is responsible for protecting agriculture from invasive species, does the lion’s share of federal rapid response. In fiscal year 2000, APHIS estimated that it spent $125.8 million for rapid response—about 85 percent of the estimated $148.7 million federal agencies spent on this activity. About $113.7 million of APHIS’ funding went toward species that primarily threaten crops or livestock. All told, total federal rapid response funding for species that primarily affect agriculture was reported to be about $118 million. Most of APHIS’ rapid response funding was spent on relatively few invasive species. APHIS’ biggest expenditure, almost $81 million, was for citrus canker, a highly contagious bacterial disease that affects Florida’s citrus crops. This effort entailed tree removal, destruction, and replacement.