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Invasive Species

Top 100 invasive species in Oregon

Invasive Species

The spread of non-native invasive species during the last century has been unprecedented in Earth's history, with the speed and scale of these infestations more rapid than natural invasions. The spread of non-native species in human-disturbed habitats reflects a deterioration of the North American landscape.

Invasive species disrupt the functioning of native ecosystems upon which humans depend. Many non-native species become pests by rapidly dispersing into communities in which they have not evolved, and by displacing native species because of evolutionary mismatches. For example, non-native species contributed to 68% of the fish extinctions in the past 100 years, and the decline of 70% of the fish species listed in the Endangered Species Act (Lassuy 1994).

An "invasive species" is defined as a species that is 1) non-native (or alien) to the ecosystem under consideration and 2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health.

Invasive species can be plants, animals, and other organisms (e.g., microbes). Human actions are the primary means of invasive species introductions. One study estimates that the total costs of invasive species in the United States amount to more than $100 billion each year. Invasive species impact nearly half of the species currently listed as Threatened or Endangered under the U.S Federal Endangered Species Act.

Aquatic Life: Invasive Species

Aquatic nuisance species are non-native invasive species that threaten the diversity or abundance of native species or the ecological stability of infested waters, or commercial, agricultural, aquacultural or recreational activities dependant on such waters. Invasives include non-native species that may occur in inland, estuarine and marine waters and that presently or potentially threaten ecological processes and natural resources. In addition to adversely affecting activities dependant on waters of the United States, invasive non-native species adversely affect individuals, including health effects.

Invasive species are any species or other viable biological material that enters an ecosystem beyond its historic range, including any such organism transferred from one country into another. Invasive non-native species (also known as introduced, foreign, alien, and immigrant species) include both exotics and transplants.

Top 100 Most Invasive Species in Oregon

One invasive plant, purple loosestrife, can produce up to 2.7 million seeds per plant yearly and spreads across approximately 1 million additional acres of wetlands each year.

The glassy-winged sharpshooter, an invasive insect detected in California, carries with it the plant bacterium Xylella fastidiosa, a disease that has caused nearly $40 million in losses of California grapes. The disease poses a major threat to grape, raisin, and wine industries, as well as the tourism associated with them. Collectively these are valued at nearly $35 billion annually.

The Oregon Invasive Species Council maintains the most current list of the Top 100 most invasive species in Oregon. The list is categorized by type of invader, such as micro-organisms, aquatic plants, fish, mammals and others.

Additional Resources

USDA Forest Service. Pacific Northwest Region. Invasive Species Links and Contact. Includes lists of governmental and non-governmental sites.

Oregon WeedMapper