Healthy, ecosystems are vital to plant, animal, and human life. Natural and managed ecosystems facilitate vital environmental processes such as air and water purification, waste decomposition, and carbon sequestration. Introducing unwanted species can affect the ecosystem health and productivity of natural and managed systems.
The destructive consequences of rabbit infestations and the introduction of the American grey squirrel into Europe are well known, but there are many other examples: the Harlequin ladybird, from Asia, poses a deadly threat to native ladybirds and other insects in Europe; coypu, mink and musk rat, brought from America for their fur, are now wild in Europe, damaging canals and flood protections systems and decimating indigenous species such as water voles; Japanese knotweed Fallopia japonica , which was introduced to Europe from eastern Asia as an ornamental plant in the 19th century, is causing damage to natural plant and insect species across the continent; and there is widespread agreement that the alarming decline in global bee numbers is at least partially attributable to the spread and impact of pests such as the Varroa mite.
Since , more than one species per year has become established, a rate that shows no sign of declining. As well as inflicting significant damage to the environment and ecological services, invasive species can pose a threat to humans.
The Asian tiger mosquito Aedes albopictus , which arrived in Europe through the trade in used car tyres, has been linked to the transmission of more than 20 human pathogens, including yellow fever and dengue. Alien plants such as the ragweeds Ambrosia sp. Invasive species have also been implicated in the spread of viruses such as flu and HIV.
Invasive alien species can be expensive for their new host countries. For example, Dutch elm disease — caused by an introduced fungus — has devastated elm trees in Europe, and the pine wood nematode Bursaphelenchus xylophilus , thought to have originated in North America, has worked its way to Portugal and is causing severe damage to certain species of pine.
The American grey squirrel not only out-competes the native red squirrel — it carries parapoxvirus, which is devastating to red squirrels — in Italy and the UK but damages coniferous trees and reduces their value as timber. This does not take into account the cost of major human pathogens or outbreaks of animal diseases.
The UN target is also included in the EU biodiversity strategy. It suggested a number of options to reduce the likelihood of further spread. In March an opinion on the risks posed by South American potato cyst nematodes Globodera pallida and Globodera rostochiensis to solanaceous plants such as potatoes and tomatoes concluded that existing phytosanitary measures are important to prevent entry of new virulent genotypes of the pest.
Also in , the PLH Panel delivered an evaluation of the pest risk analysis for the Spanish territory of the island apple snail Pomacea insularum , prepared by the Spanish Ministry of Environment and Rural and Marine Affairs.
Apple snails, originating in South America, are serious pests of rice and can have devastating effects on natural wetlands. The Panel subsequently published a detailed assessment of the potential establishment of the apple snail in the EU territory, followed in April by an environmental risk assessment of the apple snail, which showed potentially strong negative impacts on biodiversity , ecosystem functioning and ecosystem services in the wetlands of southern Europe.
The Panel reviewed several measures to limit or prevent spread within the EU of silverleaf whitefly Bemisia tabaci in an opinion published in April Bergersen, E. The distribution and spread of Myxobolus cerebralis in the United States. Fisheries Bounds, D. Marsh Restoration: Nutria Control in Maryland. Pilot Program Proposal. Fish and Wildlife Service, Washington, D. Bram, R. Introduction of nonindigenous arthropod pests of animals.
Burridge, M. Heartwater: An increasingly serious threat to the livestock and deer populations of the United States. In Proceedings, st Annual Meeting of the U. Animal Health Association. Spectrum Press, Richmond, Virginia. Simmons, and S. Introduction of potential heartwater vectors and other exotic ticks into Florida on imported reptiles.
J Parasitol Simmons, B. Simbi, T. Peter, and S. Evidence of Cowdria ruminantium in Amblyomma sparsum ticks found on tortoises imported into Florida. Isolation of Vibrio cholerae 01 from oysters, Mobile Bay, Morb Mortal Weekly Rep Civeyrel, L. A tale of two snails: Is the cure worse than the disease? Biodiversity Conserv Corn, J. Barre, B. Thiebot, T. Creekmore, G. Garris, and V. Potential role of cattle egrets, Bubulcus ibis Ciconiformes:Ardeidae , in the dissemination of Amblyomma variegatum Acari:Ixodidae in the eastern Caribbean.
Corn, M. Buckl, J. Rawson, and E. Invasive Plant Species. Issue Paper Number Crooks, J. Lag times in population explosions of invasive species: Causes and implications. Sandlund, P. Schei, and A. Viken eds. Eden, W. Brush, H. Cox, C. Kingsolver, D. Lovitt, and F. Department of Agriculture, Washington, D. Fuller, P. Nico, and J. American Fisheries Society, Bethesda, Maryland. Getz, C. Legal implications of eradication programs.
Dahlsten and R. Garcia eds. Eradication of Exotic Pests. Goetz, R. Exotic invaders. Agricultures 3 Summer Purdue University, West Lafayette, Indiana. Groombridge, B. Jemal, A. A review of the red imported fire-ant Solenopsis invicta Buren and its impacts on plant, animal, and human health. Prev Vet Med Johnson, D.
Distribution and dispersal of Cactoblastis cactorum Lepidoptera: Pyralidae , an exotic Opuntia -feeding moth, in Florida. Fla Entomol Jurek, R. Domestic ferret issues in California. California Dept. Kock, N. Van Vliet, K. Charlton, and F. Detection of Cowdria ruminantium in blood and bone marrow samples from clinically normal, free-ranging Zimbabwean wild ungulates.
J Clin Microbiol Lever, C. Quiller Press, London. Louda, S. Kendall, J. Connor, and D. Ecological effects of an insect introduced for the biological control of weeds. Science Mahan, S. Peter, B. Simbi, K. Kocan, E. Camus, A. Barbnet, and M. Comparison of efficacy of American and African Amblyomma ticks as vectors of heartwater Cowdria ruminantium infection by molecular analyses and transmission trials. McClure, M. Reshaping the ecology of invading populations of hemlock woolly adelgid, Adelges tsugae , in eastern North America.
Biol Invasions McGregor, R. Butler, A. Fox, D. Johnson, C. Kingsolver, B. Levy, H. Pritchard, and R. The Emigrant Pests. McMichael, A. Global changes, invasive species, and human health.
Mooney and R. Hobbs eds. Invasive Species in a Changing World. Island Press, Washington, D. Moyle, P. University of California Press, Berkeley, California. Myers, J. Simberloff, A. Kuris, and J. Eradication revisited--Dealing with exotic species. Trends Ecol Evol Global Change Ecosystems Research Report. National Research Council, Washington, D. Oberem, P. Heartwater in hosts other than domestic ruminants.
Onderstepoort J Vet Res Obrycki, J. Elliott, and K. Coccinellid introductions: Potential for and evaluation of nontarget effects. Follett and J. Duan eds. What type of harm does an invasive species do? Since invasive species are in a new environment, free from natural predators, parasites, or competitors, they often develop large population sizes very rapidly.
These high populations can out-compete, displace or kill native species or can reduce wildlife food and habitat. Some also have the potential to disrupt vital ecosystem functions, such as water flow, nutrient cycling, or soil decomposition. Other invasive species cause massive amounts of economic damage to the agricultural business by destroying crops and contaminating produce. Some invasive species can cause direct harm to humans or domestic animals.
Why are the species on this website of concern to North America? Why don't our native plants have resistance to these exotic pests? Plants developed resistance to pests through their interaction with the pest over many generations. The plants that were resistant survived to pass their survival characteristics on to the next generation.
As a result, the plant species develops a set of effective defenses that allows the species to survive. When a new pest is introduced, the defenses of the plant are not prepared to counter the attacks of the new pest; therefore significant losses are often experienced.
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