It includes loss of western rangelands to invasive plants, blockage of power plant intakes to invasive mussels, and major declines of birds and mammals to invasive snakes in the Everglades. So vast is this "bioinvasion" (as some have termed it) that only rough estimates can be made of the numbers of non-native species now in North America or in the rest of the world. Moreover, despite a few rare successes, eradication of these species, once they become established, is extremely improbable. But because of the number and variety of non-native species, it is unclear how best to manage or prevent these effects or what legislation would be needed to address these problems. The absence of a general federal responsibility for wildlife affects the federal role in addressing invasive species. The National Invasive Species Council (NISC) was created by Executive Order 13112 in 1999, and has addressed some aspects of the invasive species problem. However, legislative efforts to date have tended to focus on well-established problems: the invasion of a single species, a specific pathway of introduction, or damage or risks to agriculture. The mild climates of Hawaii and Florida make it easier for the rich flora and fauna from other tropical and semitropical regions to survive, and they also make the states attractive to businesses that import, maintain, or breed non-native animals and plants, such as tropical fishes and ornamental plants. Easy transportation access increases the likelihood of invasion in aquatic habitats such as the Great Lakes. The areas around airports, with increased levels of international traffic and tourism, also are at risk. The arrival of a number of beetle species has played a similar role in focusing attention on pallet wood, packing crates, live plants, and airport warehouses as pathways and centers of biotic invasion. This evidence may be based on experience with the species domestically or in other countries. Preventing the spread of the species after it enters the United States may rely on public education, penalties for shippers, monitoring, and other means. This approach allows more flexibility for industries that depend on the importation of new species of plants or animals. With the white list approach, there is an attempt to predict potential harm before a species' arrival. Any species not on the list would be excluded. Issues for Congress: Actions and Approaches

Federal laws concerning invasive species form a patchwork, stronger in some areas, such as agriculture and ballast water, and weaker or absent in other areas. Current laws do not clearly address
prevention of biological invasion across foreseeable pathways (with the exception of ship ballast water); or early detection and rapid response (EDRR) before the establishment of the new species, when the focus of effort shifts from less expensive prevention to more expensive and less efficient control. Approaches to Regulation: Species-by-Species Versus Pathways

Legislation to address invasive species could take a species-by-species approach, a pathway approach, or a combination of the two. Both agencies would benefit from faster assessments of either species or pathways so they could direct resources to the most critical areas. Its goals put prevention on an equal or higher footing compared with control of species that are already established. The list below is compiled from many sources. Review of industries dependent on importing and transferring non-native species . Since the creation of NISC, agencies have begun to respond across a broad front in the days, weeks, or months after an invasion is discovered.
For the first few centuries after the arrival of Europeans in North America, plants and animals of many species were sent between the two continents. The transfer of non-natives consisted not only of intentional westbound species ranging from pigs to dandelions but also of intentional eastbound species, such as gray squirrels and tomatoes. And for those centuries, the remaining non-native species crossing the Atlantic, uninvited and often unwelcome, were ignored if they were noticed at all. They were joined by various species arriving deliberately or accidentally from Asia and Africa. The national focus on invasive species arose in the 19 th century, primarily owing to losses in agriculture (due to weeds or plant diseases), the leading industry of the time. A few recently arrived invasive species, and estimates of adverse economic impacts exceeding $100 billion annually, have sharpened that focus.
Very broadly, the unanswered question regarding invasive species concerns whose responsibility it is to ensure economic integrity and ecological stability in response to the actual or potential impacts of invasive species. As this report shows, the current answer is not simple. It may depend on answers to many other questions: Is the introduction deliberate or accidental? Does it affect agriculture? By what pathway does the new species arrive? Is the potential harm from the species already known? Is the species already established in one area of the country? Finally, if the answers to any of these questions are unsatisfactory, what changes should be made?
The specific issue before Congress is whether new legislative authorities and funding are needed to address issues related to invasive species and their increasing economic and ecological impacts on such disparate matters as power plant operations, grazing lands, and coral reef fishes. Such legislation could affect domestic and international trade, tourism, industries dependent on importing non-native species and those dependent on keeping them out, and, finally, the variety of natural resources that have little direct economic value and yet affect the lives of a broad segment of the public.
In the century or so of congressional responses to invasive species, the usual approach has been an ad hoc attack on the particular problem, from impure seed stocks to Asian carp in the Chicago Sanitary and Ship Canal. A few notable attempts have begun to address specific pathways by which invasives arrive (e.g., ship ballast water), but no current law addresses the broad general concern over non-native species and the variety of paths by which they enter this country. A 1999 executive order took a step in bringing together some of the current authorities and resources to address a problem that has expanded with both increasing world trade and travel and decreasing transit time for humans and cargo. Multiple bills have been introduced on this subject in recent Congresses as well as in the 114 th Congress.
There are two basic approaches to addressing invasive species: a species-by-species assessment of the risks or benefits of admitting or excluding species, and a policy based on controlling pathways of entry in which vigilance is maintained on incoming ballast tanks, cargo holds, packing materials, and similar vehicles for unwanted organisms. These two approaches may complement each other. Policymakers also have the choice of an emphasis on preventing the arrival or establishment of more invasive species versus post hoc control of species that have already arrived and become established.