Agriculture Reference
In-Depth Information
plant yearly and spreads across approximately 400,000 additional hectares of
wetlands each year. These strategies demonstrate the impact of an invasive
species on a natural habitat.
Invasive plants damage soil and water resources. The displacement of
bunch-grasses by spotted knapweed (Centaurea maculosa Lam.) substantially
increases surface water run-off and sediment yield (soil loss). An additional
16,200 kg of soil would be lost from a 225-hectare rangeland infested with
spotted knapweed in western Montana during an average 30-minute rainfall
event, compared to a similar site occupied by native bunch-grasses [25].
Invasive plants may have impacts on endangered species in relation to their
own habitats, competitive ability, and environmental stress factors. Rare spe-
cies appear to be particularly vulnerable to the environmental changes that are
brought about by non-native species. In California, it has been estimated that
30 of the state's endangered plant species are threatened by non-native
invaders [7]. In Florida, Australian pine has spread to such an extent in coastal
areas that it is interfering with nesting sea turtles and crocodiles [13].
Invasive plants reduce available winter forage for wildlife. Spotted knap-
weed invasion of bunchgrass sites in western Montana reduces available win-
ter forage for elk as much as 50-90%. Since a highly productive foothills site
in western Montana can produce an average of 2,016 kilogram of forage grass
per hectare, forage loss from spotted knapweed can be as high as 1,315 kilo-
gram per hectare [25].
Human and sociological dimensions
The human or sociological dimension in relation to species invasion is not
often examined for its significance. The human dimension is considered to be
the elements or social factors that are influenced by human actions in our soci-
ety. Historical perspectives, economic impacts, educational component, socio-
logical stature, political acceptance of the stature, and regulatory aspects,
including national and international laws are viewed as human dimensions. In
reality, the human dimension has significantly impacted the current status of
global invasive species.
Historical status of invasive plant species
The importance of invasive species changes over time as we continue to iden-
tify and assess many of the invasive species. This status may be inflicted by
many aspects of the human dimensions.
Kudzu ( Pueraria montana var. Iobata (Wild.) Maesen & S. Almeida) demon-
strates why the historical information can be important. Kudzu is a tall-climb-
ing perennial vine from eastern Asia. The Japanese government first exhibited
kudzu as an ornamental vine at the Philadelphia Centennial Exposition in 1876.
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