Wetlands moderate the flow of nutrients and sediment running off the land
and regulate the flow of water moving downstream. They clean water by
absorbing and filtering pollutants that would end up in lakes, rivers, and
groundwater. They buffer riverbanks and lake shores from the eroding
effects
of currents and waves. By absorbing spring runoff, they take the punch out
of floodwaters. Wetlands produce as much plant and animal life as do
similarly sized areas of rain forest. Wetlands affect, and are affected by,
the forests, prairies, lakes, streams, and rivers around them. Movement of
wildlife, water, and nutrients is critical for sustaining all ecosystems,
including wetlands (Minnesota Audubon Council, 1993).
Wetland complexes, which include a variety of wetland types, are crucial to
many wildlife species and support a wide range of biological diversity.
Many
wildlife species can only find all the diverse food and habitats they need
by using a combination of wetlands and other ecosystems. For example,
seasonal and temporary wetlands warm early in the spring, and provide food
for waterfowl at a time when larger, deeper wetlands are still frozen. They
provide ideal feeding sites in terms of abundance and availability of
high-protein foods throughout the spring and early summer. As they dry up,
feeding shifts to semi-permanent ponds and lakes where adult insects are
beginning to emerge (Swanson et al. 1974).
To learn more about the status of wetlands in the United States, see the
National Wetlands Inventory Web Site.
Wetland Restoration
Restoring wetlands is often simply a matter of destroying manmade drainage
facilities and letting water and vegetation return to the site naturally.
The same tools used to destroy wetlands are used to restore them. If a
wetland is drained by underground tile, a section of the tile is uncovered,
removed, and the area is backfilled with soil. Wetlands that are drained by
ditches are restored by the construction of an earthen ditch plug at the
outlet to the wetland. A pipe or earthen spillway is used to regulate water
levels and provide for overflow. On larger wetlands, a water control
structure may be installed that allows a periodic drawdown of the wetland
in
an attempt to mimic the natural wet-dry cycle of many basins.
After restoration, wetland plants begin to reappear. The seeds of some
wetland species can lie dormant, but viable, for as long as thirty years,
waiting for moist conditions to return. These species will be among the
first to appear after restoration, often even after years of agricultural
herbicide use. Other seeds are carried into the wetland basin by birds,
wind, and floods. It is generally not worth the cost to attempt to
revegetate a wetland; if the conditions are right for a species, it will
find its own way into the restored basin.
If you are interested in restoring a wetland on your property, check out
our
Partners for Fish and Wildlife Program.
Moist Soil Management
When mud flats are exposed by summer drawdowns of water levels, moist soil
plants develop. These plants have the potential to produce high seed yields
that serve as an important food source for waterfowl and other wildlife.
When compared with grain from agricultural fields, moist soil plants may
provide waterfowl with lower levels of metabolizable energy, but they
contain a better balance of nutrients (Fredrickson and Taylor 1982,
Fredrickson 1991, Havera 1992).
A diversity of invertebrate and vegetative foods from different wetland
types are needed on fall and spring migration areas to meet the changing
nutritional demands of waterfowl and provide them with a complete diet.
Although mallards like corn, studies show that if they are fed only corn,
even when supplemented with oyster shells to provide calcium and grit, they
begin to die after about 60 days (Havera, 1996).
Many restored or enhanced wetlands are equipped with stop log structures that allow the
manipulation of water levels. This manipulation permits us to control the drawdown of water levels in a way that provides optimum moist soil
plant growth. Water levels are slowly increased in the fall to provide the
desired mix of open water and mature flooded moist soil vegetation.
References
Fredrickson, L.H. 1991. Strategies for water level manipulations in moist-soil systems. Waterfowl Management Handbook, Fish and Wildlife Leaflet 13.4.6. 8 pp.
Fredrickson, L.H. and T.S. Taylor. 1982. Management of seasonally flooded impoundments for wildlife. Fish and Wildlife Service Resource Publication 148. 29 pp.
Havera, S.P. 1992. Waterfowl of Illinois: status and management. Final report to Illinois Department of Conservation. W-110-R-2. 1,035 pp.
Havera, S.P. (Illinois Natural History Survey). November 1, 1996. Personal Communication with Susan B. Julison.
Minnesota Audubon Council. 1993. Minnesota Wetlands: A primer on their nature and function. Ed. Cheryl Miller. Saint Paul, Minnesota. 23 pp.
Swanson, George A., M.I. Meyer, and J.R. Serie. 1974. Feeding ecology of breeding blue-winged teals. Journal of Wildlife Management. 38(3):396-407
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