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Threats to Biodiversity
V.1 Causes
Multiple
Stresses
Habitat
Loss
Ozone
Depletion
Climate
Change
Introduction
of Exotic Species
Pollution
V.2 Scale
Local
Populations
Species
Entire
Ecosystems
Wetlands
as an Example of Habitat Loss
Definition:
A wetland is an area where water covers the soil, or is present at, or
near the surface of the soil for part, or all of the year. Legally, a
wetland has to have three characteristics present during part of the growing
season: hydrophytic vegetation, hydrophytic soils, and appropriate hydrology.
Hydrophytic vegetation typically includes cattails, bulrushes, willows,
and sedges. Hydric soils are developed in areas where soil was oxygen
limited for long periods. Soil surveys and other indicators such as the
Munsell soil charts can be used to determine if hydric soil is present.
Hydrology indicators can be determined with a field identification of
standing/flowing water, water marks on trees, drift lines, or sediment
layers. The Army Cops of Engineers (ACOE) maintains wetland delineation
maps that show where many of the larger wetlands are located.
Uses:
Wetlands are valued as an ecological resource, but are also valued for
storage for floodwaters, natural water quality treatment (silt, nutrients,
toxins), prevention of saltwater intrusion, shoreline stabilization, and
recreation.
Why Losses?
Wetlands now occupy less than 5% of land acreage in the United States.
In the lower 48 states, 1/2 of wetland acreage has been lost. Historically,
public policies served to destroy wetlands, e.g. government subsidies
in the 1930s and 1940s for conversion to farmland (87%), use as landfills
up until 1977 (5%), and use as building space for highways and housing
developments (8%).
Permits/Regulations:
Since 1972, to be able to fill, excavate, or mechanically clear in a wetland,
lake, river, or stream, you need a Clean Water Act discharge permit. These
are known as Section 404 permits and are granted if the applicant can
show that the project will not have an unacceptable adverse impact on
the ecosystem. The applicant typically applies to the ACOE for the section
404 permit. If a permit is needed, the applicant also needs a Section
401 water quality certification from the state environmental agency. The
agency reviews the application to see if the activity complies with the
water quality standard, and typically requires measures to minimize impacts.
Often the applicant is required to compensate for the impacts. Permits
can be denied.
Other
Protection: The 1985 Farm Bill further protects wetlands from drainage,
fill, or damage. The difficulty is often delineating the wetland and then
determining if the project will have negative impacts. Several programs
also exist to restore degraded wetlands and build new ones. These are
administered by several not profit groups, the Fish and Wildlife Service,
and the Department of Agriculture's Wetland Reserve program. Constructed
wetlands are also being used for controlled stormwater and wastewater
treatment.
V.3 Implications
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