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Invasive Plant Information
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Do weeds differ from invasive plants, exotics, or
aliens?
The terms alien, invasive,
exotic and weed are often used inter-changeably to describe unwanted plant
species. The term weed
represents any plant that is growing where someone doesn’t want it. The terms alien and exotic are used
interchangeably to describe an unwanted plant that has been introduced to an
environment by humans, or is non-native. Weeds may or may not be non-native.
Invasive species are
distinguished from other unwanted plants by their ability to spread (invade)
into native ecosystems.
Invasive species are typically non-native, however, not all non-native
species are invasive.
For the purposes of this EIS an invasive plant is defined as “a
non-native plant whose introduction does, or is likely to, cause economic or
environmental harm or harm to human health”. Non-native means, with respect to a particular
ecosystem, any species that is not native to that ecosystem.
What invasive plants are degrading National
Forests in the Pacific Northwest?
Forests throughout the
Pacific Northwest Region are in the process of submitting their most current
inventory of invasive plants to the EIS team. To date, Forests have reported the occurrence of 121
individual species of invasive plants.
Click below to see the list of the species that have been submitted to
date:
Species
submitted to date
For a general visual image
of where invasive plants are concentrated throughout the Region click below
and link to a map from the Regional Invasive Plant Program.
Pacific Northwest Region
weed page
What are the impacts of invasive
plants?
 Invasive
plants can displace the native plants that provide food and shelter for
wildlife. Their presence also
reduces the quantity and quality of forage available for both big game and
domestic livestock. Some
invasive plants are poisonous or can cause injury to wildlife and livestock. The page linked below has information
on a very unsuspected impact of invasive plants:
How
invasive plants affect wildlife
Invasive plants out-compete and eliminate
native plants. As invasive
populations rise, native species populations fall. This results in a
reduction in species diversity, changes in community structure and loss of
ecosystem function.
Invasive
plants increase soil erosion.
Research has shown that invasive species can reduce organic litter
found in native bunch grass ecosystems and cause increased topsoil loss
during rainfall.
Invasive
plants diminish or eliminate recreation opportunities. Many invasive plant species have
thorns or spikes that are painful to recreationists. The presence of these plants also
impacts the visual quality and general esthetics of the recreation
experience. In addition, reduced
forage and spawning habitat results in diminished hunting and fishing
opportunities.
Invasive
plants can alter the natural fire cycle of plant communities.
Invasive species impact nearly half of the
species currently listed as Threatened or Endangered under the U.S Federal
Endangered Species Act. A local
example of this is the encroachment of yellow star thistle on the Endangered
MacFarlane’s four o’clock in Hells Canyon.
FOR MORE INFORMATION
Please see our Frequently Asked
Questions page.
Invasive plant related handouts..
Umatilla NF Weed Prevention Poster
Wallowa Whitman NF Advisory Poster
Idaho Forests Trailhead poster
Coloring book put out by Washington State Noxious Weed control board.
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