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Over the
last century we have seen outstanding technological
advancements and economic expansion. These improvements
have enabled humans to travel faster and more freely, conduct
global
trade, create possibilities for new recreational activities, etc. Along with these advantages we have experienced negative effects, including the spread of detrimental plants outside of their native habitats to other parts of the world. Initial introduction of plants to other countries could be the result of intentional action such as to benefit the timber industry or for agricultural purposes, or non-intentional such as dispersal as a result of travel and commercial activities. If used for horticultural purposes, some of these plants could escape their cultivated habitats, and become highly abundant. In the case of accidental introduction as a result of travel or trade, it could be quite some time before detecting the new invaders. In the US these plants of foreign origin are generally referred to as exotic species. Once they are widespread in their newly found habitat, they have the potential to cause harm to the native flora, thus becoming invasive species. As a result, invasive species can have negative economic impact and can threaten native biodiversity and ecosystem function (Kolar & Lodge, 2001). Invasives that have high impacts on the economy or the environment may be declared noxious by state or provincial governments and subject to regulation.
Current
mechanisms to prevent species from entry into the United States based on their invasive potential are largely ineffective (Westbrooks, 1991). The Federal Noxious Weed Act provides the main authority for the restriction of “weeds” from entry into the U.S. (Reichard & Hamilton, 1997). Reichard points out that the Act has been largely ineffective for a number of reasons, primarily because it targets only a small list of species known as agricultural pest plants and because of inadequate funding. She outlines four possible strategies for screening the invasive potential of new species, including calling for “an informed estimate…” In particular, the informed estimate strategy would rely on developing a predictive model for evaluation of invasive potential based on what is already known about other invasive species.
Currently
there are 554 known exotic plants in the Idaho plus Montana
(Rice, P.M., 2002). Already 89 of them have
been declared as “noxious” by the regulatory state
agencies in the five Pacific Northwest States. “Noxious weed”
is a legal term used by agencies in their respective states,
with every state having a somewhat different process for
designating plants as noxious weeds. However, these noxious
weeds all share the same invasive behavior, including
causing significant environmental and economic damage.
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