Wetlands, unique ecosystems home to a great diversity of terrestrial and aquatic plants and animals, are beneficial in many ways. They improve water quality by filtering and accumulating pollutants, thereby protecting adjacent rivers, lakes, and streams. Wetlands provide food and protection for many of the nation's fish and wildlife species, including endangered and threatened species. Finally, wetlands have economic value associated with recreational, commercial, and subsistence use of fish and wildlife resources.
Over time, many wetland, riparian, and lakeshore environments have become degraded by human-induced disturbances, such as the introduction of invasive, non-native plants. Such exotic vegetation often reduces habitat quality (e.g., loss of food supply) by outcompeting native vegetation. It contributes to an unkempt, weedy appearance, and obscures the waterbody from view. Such disturbances have not only affected the natural functions of these systems by increasing erosion, reducing natural wetland vegetation, and degrading habitats, but they have diminished the aesthetic value of the environment.
Land development activities in adjacent areas and in upland areas within the watershed also disturb wetlands and waterbodies. These disturbances often result in sediment deposition, nutrient enrichment, and increased stormwater flows into the wetlands. This causes a reduction in water clarity that limits the growth of wetland plants and submerged aquatic vegetation, smothers streambeds, contaminates water quality, and alters natural hydrology.
Municipalities can plant wetland species to preserve existing wetlands and to enhance degraded wetland plant communities. Wetland plantings, however, are only a part of restoring, protecting, or creating a wetland.
When preserving and enhancing degraded wetlands, it is often necessary to plant wetland species along shorelines, in upland habitats, and along the bottom of waterbodies. Each wetland can be divided into specific zones based on soil hydrology. Upland transitional zones are adjacent to normally wet or inundated wetland areas. These zones are extremely important to the health, function, and appearance of the wetland or waterbody. Wetland and open water zones range from having saturated soil below the ground surface (such as in a wet meadow) to being completely inundated with water (such as a shoreline or streambank). These areas can support a variety of wetland plant species, including those that are intolerant of inundation, emergent species, and submerged or floating plants.
When preserving degraded wetland communities, municipalities can also use wetland mitigation banking. A wetland mitigation bank is a wetland area that has been restored, created, enhanced, or preserved, and then set aside to compensate for future wetland conversion from development activities. A municipality can participate in wetland mitigation by undertaking such preservation activities under a formal agreement with a regulatory agency. In Pembroke Pines, Florida, 358 acres of degraded wetlands on city property were restored through the Florida Wetlands Bank. In King County, Washington, a wetland mitigation banking program has also been established. See the King County Wetland Mitigation Banking Program website for more information on this program.
Obtain a permit. When beginning a wetland planting, it is important to remember that any entity that alters a wetland must first get a permit from the U.S. Army Corps of Engineers. This requirement is specified under the Clean Water Act, Section 404.
Determine the site history. The first step in a wetland planting program is to determine a site's history, including previous vegetation and typical conditions. Another important factor is a site's hydrology. Hydrology defines such factors as average and maximum depth, duration of inundation, and degree of soil saturation. Hydrology affects the soil and plant conditions that characterize different wetland types and streambank and shoreline environments. Municipalities should work with a reputable wetland firm to determine these conditions. Other factors that should be considered for wetland plantings are described below.
Select plants and begin planting. Selection of plants for wetland, streambank, and shore zones is closely tied to the hydrology of the site, particularly water depths and flood durations. Other factors such as shading, water clarity, and salinity should also be taken into account. Planting in open water areas typically involves the use of tubers, plugs, and potted plants. Often both seeds and live plants are used when planting in nonponded wetland zones. Project planners must be familiar with different types of plants that can be used, depending on the site's characteristics. Field tests can be useful to delineate planting zones on a site that contains a range of hydrologic regimes.
It is important to use a diverse mix of wetland plants and not just one type of plant such as Phragmites (reed grass) or cattails. These and other aggressive species are very easy to establish but should not be planted since they may outcompete valuable species and will eventually dominate less robust colonizers.
It is important to establish riparian vegetation in riparian wetlands, which exist adjacent to streams. Riparian vegetation stabilizes banks, provides large woody debris and detritus for aquatic habitat and food, and shades the stream, reducing water temperatures. Reestablishing riparian cover along streams can call for active reforestation of native species, removal of exotic species, or modification of mowing options to allow gradual succession.
The types of vegetation planted should depend upon geographic location, climate, and soil conditions. Species native to the area are naturally better suited to its conditions. Riparian vegetation includes ground cover like grasses, sedges, and rushes as well as woody plants, such as shrubs and trees. While all of these plants help stabilize stream banks and filter stormwater, their effectiveness varies. For example, deeply rooted plants like trees might work better than some shallow rooted plants for transforming or retaining nitrogen because the roots can reach deeper flowing water and accumulate larger amounts of nitrogen.
Information on selecting native plant species, the timing and techniques of planting, and other local factors is available from federal agencies, such as the Natural Resources Conservation Service, and from various state and local agencies. A local Cooperative Extension Service is another good source of information.
Initial and long-term management and maintenance. Many wetlands become overgrown with non-native, invasive plant species following a disturbance. Noxious weeds can be controlled in a variety of ways. Controlled burning is a commonly used technique for wetlands, natural streambanks, and shorelines. Timing is important, however, since these areas burn well only at specific times of the year. Furthermore, fires in wetland areas can be intense, especially where cattails and giant reed grasses are present; therefore, special care should be exercised. A two- to three-year rotation for prescribed burnings is often appropriate.
Invasive species can also be removed by physically extracting them from the site. This process is often difficult because many non-native species grow in dense patches with extensive root systems.
For species that are particularly difficult to eliminate using prescribed burning or physical extraction approaches, chemical control of non-native species is sometimes warranted. Herbicide techniques are different from those used in upland sites, primarily because herbicides have to be licensed for use in or near waterbodies, wetlands, and other aquatic systems. Chemical means of weed reduction should be used only when necessary, and product labels should be read and closely followed. Only a licensed herbicide applicator should conduct this work.
If hydrologic and soil conditions are conducive to plant growth, wetland plantings often respond very quickly. Extensive cover of native plants often can be achieved during the first growing season. Noxious weed control through the use of mowing or pruning is often necessary during the first several years. Some replanting might also be necessary. A stable, diverse, and aesthetic wetland/riparian landscape might take three to five years to achieve.
It is important to understand that the success of wetland plants will not be immediate, nor will the effort end with the planting itself. Wetland plants should be routinely monitored following planting. If the plantings do not appear to establish themselves, it is important to reevaluate the site selection and conditions before replanting. With each revegetation effort, both successful and unsuccessful, new information about suitable habitat and conditions will be gained.
Planting programs benefit wetlands in several ways. First, these plantings act as a "jump-start" for bare or significantly disturbed areas. Although revegetation might not completely cover a disturbed area, it helps establish plant species that can then propagate. Planting indigenous aquatic species helps restore the natural functions of wetlands. These functions include stormwater infiltration and filtration, nutrient uptake, sediment removal, and peak flow attenuation. Second, revegetation programs help educate the public about the value of wetland plants. Working on wetland planting projects provide the public with a hands-on opportunity to improve wetlands and aquatic environments. Wetland planting projects also help scientists identify the environments and growing conditions that promote plant growth. Finally, reestablishing wetland vegetation improves wildlife habitat for migrating waterfowl, reptiles, amphibians, and other aquatic species.
For example, West Eugene, Oregon's, Stream Team and Parks Volunteer programs have prompted several area agencies and organizations to adopt wetlands, stream segments, and parks (City of West Eugene, Oregon, 2001).
The success of new plantings depends on several factors, including weather (drought or flood) and insect damage. Also, upstream or nearby development and land use changes may alter wetland conditions and result in altered salinity, hydrology, or other factors that can kill recently planted vegetation. Maintenance ensures that the plantings have successfully established themselves.
Other problems associated with wetlands include the filling in of detention ponds originally built by developers. When filling occurs, municipalities should determine whether they should convert the ponds into wetlands or return them to their original state.
Local or regional environmental agencies often sponsor wetland planting programs. Many organizations use fund-raisers and membership dues to earn money for replanting activities. Scientists and wetland experts often donate their time to conduct site visits and provide recommendations for the plant species selection process.
Briggs, M.K. 1996. Our National Wetland Heritage: A Protection Guide. University of Arizona Press, Tucson, AZ.
Briggs, M.K. 1996. Riparian Ecosystem Recovery in Arid Lands: Strategies and References. University of Arizona, Tucson, AZ.
The Izaak Walton League.2000. American Wetlands Campaign. [http://www.iwla.org/index.php?id=214 ]. Accessed September 12, 2005.
Kentula, B., G. Holland, and S. Sifneos. 1993. An Approach to Decision Making in Wetland Restoration and Creation. CRC Press, Boca Raton, FL.
King County Water and Land Resources Division. 2000. King County Wetland Mitigation Banking Program. [http://www.kingcounty.gov/environment/waterandland/wetlands/mitigation-banking.aspx ]. Accessed November 16, 2005.
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USEPA, 1995. Ecological Restoration: A Tool to Manage Stream Quality. EPA 841-F-95-007 U.S. Environmental Protection Agency, Office of Water, Washington, DC.
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