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INVASIVE
SPECIES
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| Horses are used to help
spray for noxious weeds in Oregon. Photo courtesy
of Wallowa Resources. |
Invasive species of plants and animals are displacing
and destroying native species all across our National
Forest lands. There unwelcome invaders, which are native
or non-native plants, animals, insects and pathogens
(disease causing bacterium or fungus), can cause ecological
and economic harm as well as create human health issues.
Some invasive species, such as the tamarisk in Utah
and Arizona, were introduced on purpose to control erosion,
while others, such as the Asian longhorn beetle were
accidentally introduced in wood packing crates from
China. Today, invasive species cover 3.5 million acres
of national forest land and 133 million acres in all
ownership nationwide.
New species are introduced into native ecosystems every
day, but most don’t survive or can’t reproduce.
But when conditions are right, many invasive species,
especially noxious weeds, which are invasive plant species,
can take over an ecosystem very quickly. Those conditions
usually include a lack of predators, the correct soil
type and moisture content, the availability of nutrients,
and a chemical composition that can make that plant
superior to other native plants.
Combating invasive species is time-consuming and expensive
and not well understood. Each year, the U.S. spends
$13 billion per fighting noxious weeds; invasive species
altogether cost us $138 billion per year.
The National Forest Foundation, through many of its
Grant Programs,
is helping the U.S. Forest Service and community organizations
control invasive species through education and restoration
programs.
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| Spotted
Knapweed. |
Adverse affects of
invasive species:
Invasive species
adversely affect the health of our National Forests
in numerous ways, including:
- Loss of native animal species: Of 43 native
fish species in the Southwest, 23 are listed
as endangered due to competition from non-native
species. As well, West Nile virus affects
140 species of birds.
- Loss of native plant species: Noxious weeds
push out many native plant species, especially
rangeland species such as grasses, sedges
and forbs.
- Loss of wildlife rangeland and agricultural
grazing land: Noxious weeds and other invasive
species displace, kill or weaken plants and
trees, all of which serve as food and habitat
for many foraging and grazing animals.
- Noxious weeds absorb water and nutrients
from soil otherwise needed for native plants.
- Insects kill and destroy trees and other
plants vital to forest and rangeland ecosystems.
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