Wetlands have been steadily and rapidly disappearing across the
country since the beginning of European settlement.
Montana lost approximately 27% of its wetlands between the1780's
and 1980's (See
History of U.S. Wetlands). This
is much lower than the national average.
created in the last half-century have attempted to stop the loss of wetlands
in the US, but the loss continues. (An
EPA resource for wetland laws.)
This loss is mainly associated with certain land uses. Land uses
with the greatest impact on Clark Fork Basin wetlands are:
Development: Floodplain development
often directly impacts wetlands by removing vegetation (increasing bank
erosion), and filling or draining
wetlands for building sites. Floodplain
development sometimes indirectly impacts riparian wetlands through the
installation of artificial stream stabilizing devices like rip-rap and
bulk-heads that attempt to stop the natural meandering process which creates new
wetlands and replenishes existing ones.
Road Building: Most river valleys have
roads and/or railroads. These
structures squeeze rivers and streams by narrowing the floodplain.
This destabilizes the river which has
less room to meander and therefore has an excess of energy.
The roads and railroads also affect drainage from uplands onto the
floodplains, and many are built on top of areas that once were wetlands.
Such roads often create long, low-quality wetlands upslope of the road by
interrupting surface and groundwater flows.
These wetlands can attract wildlife dangerously close to roads.
Wetland loss caused by roads is mitigated through the restoration of
other impacted wetlands although the replacement wetlands are not always of the
same type and quality as those lost. See Montana
Department of Transportation's
Off-Site Wetland Mitigation Reserves Map.
Grazing: Overgrazing harms wetlands through soil compaction, removal of vegetation,
and stream bank destabilization.
Wetlands offer some of the best forage for livestock as well as
a water source and cover, so livestock tends to spend a disproportionately
large time in wetlands. There
are many grazing strategies that discourage cattle from using wetlands. Click
web site for a discussion of these strategies.
Agriculture: Wetlands often have fairly
flat areas of rich organic soil that is highly productive agricultural land if
drained. For this reason many
wetlands have been drained and converted to agricultural lands.
Historic mining has had a major impact on wetlands of the Clark Fork basin,
particularly along the upper river where mine wastes have been deposited in the
floodplain, creating the country’s largest Superfund site. View the Superfund
EPA also list the following as major human causes of wetland loss: logging, runoff,
air and water pollution, introducing nonnative
species. See examples of nonnative species
following lists specific damaging actions commonly taken in wetlands.
Dumping: Dumping fill material
buries hydric soils and effectively lowers the water table so hydrophytic (water
loving) plants cannot compete with upland plants.
Dredging: The removal of material from a wetland or river bed.
Dredging of streams lowers the surrounding water table and dries up
Draining: Water is drained from wetlands by cutting ditches into the
ground which collect and transport water out of the wetland. This lowers the water table and dries out the wetland.
Water is diverted around wetlands, lowering the water table.
Devegetation: Vegetation plays an important role in wetland ecology by
removing water through evapotranspiration, altering water and soil chemistry,
providing habitat for wildlife, and reducing erosion.
Removal of vegetation can drastically and sometimes irreversibly alter
Damming flow: Many
ponds and reservoirs are constructed on wetlands.
A flooded wetland cannot provide the same habitats and functions.
Development of springs:
Pumping large quantities of water from springs lowers nearby groundwater
and can result in the loss of wetland vegetation.
Compaction of springs by cattle can cause springs to cease to flow.