Site selection, design criteria and performance assessment for wetland restorations in the prairie pothole region

Abstract

Between 1987 and 1991,1892 wetlands (2714 ha) were restored by state and federal agencies, most as part of the Conservation Reserve Program in northern Iowa, southern Minnesota, and southeastern South Dakota. These restored wetlands are assumed to provide wildlife habitat and improve water quality. These assumptions were evaluated by comparing features of restored wetlands to those of natural wetlands (historic or extant). A preliminary evaluation was made on all restorations; more detailed information was collected on 62 wetlands restored in 1988. The water quality evaluation is based on watershed land use, basin morphometry, and emergent vegetation development. The evaluation of restored wetlands as wildlife habitat is based on wetland type, water regime, and vegetation composition and zonation. Thirty-six of the 62 restorations do not have any part of their watershed in row-crop production and only ten had more than 50% in row crops. Earthen dams are installed on most (73%) of all restorations in the region, increasing the full pool volume and consequently the potential water residence time. However, nearly all wetlands restored by removing drainage tile (17% of all sites) have inlets positioned next to outlets, greatly diminishing water residence time at full pool. Most restorations are less than 4 ha and 41 % have soils indicating an ephemeral to seasonal pre-drainage water regime. Wetlands restored to be ephemeral/temporary are under-represented compared to their pre-agricultural extent. After three years, wet prairie and sedge meadow zones have not re established in most restorations (0% and 9%, respectively). The number of wet prairie, sedge meadow, and shallow emergent species is less than for natural wetlands. Natural wetlands have 1-22 wet prairie species, whereas restored wetlands have 0-2 species. Sedge meadow species number 7-49 in natural wetlands and 0-9 in restored wetlands. Seven to 19 shallow emergent species are present in natural wetlands, compared with 1-8 species for restored wetlands. Deep emergent and submersed aquatic zones develop in restored wetlands and the species richness of these communities is comparable to that of natural wetlands.

The influence of wetland age on bird and aquatic macroinvertebrate use of restored Iowa wetlands

“…within four years of restoration, wetlands are providing habitat for a variety of bird and invertebrate species, and are developing increasingly diverse floral and faunal populations. My study supports the results of other studies; restored prairie wetlands recover many of the plant and bird taxa typical of natural prairie wetlands , Oelphey 1991, Galatowitsch 1993. However, some invertebrates (crayfish) and vegetation zones (wet-meadow) were not present in restored wetlands.…”

“…The absence of wet meadow-zones has also been noted in other studies of restored wetlands , Galatowitsch 1993. The lack of this zone could affect restored wetland 42 recolonization by bird species, as wet-meadow areas are the preferred nesting habitat of several species, including the swamp sparrow, common yellowthroat, marsh wren, sora, and Virginia rail (Weller and spatcher 1965, Kantrud and stewart 1984.…”

“…Other programs, such as the Conservation Reserve Program and the Wetland Reserve Program, provide opportunities for voluntary wetland restoration by landowners. Although restored wetlands have been shown to support a variety of flora and fauna within a year of reflooding (Hemesath 1991, Sewell and, species richness and abundance of some bird species are lower on restored Iowa wetlands than on similar natural wetlands, and wet-meadow and low-prairie vegetation zones are missing in 6 restored basins , Galatowitsch 1993. It is not clear whether restored wetlands are unable to support the bird and plant species found in natural wetlands, or whether they have not had enough time to recolonize.…”

“…The lack of this zone could affect restored wetland 42 recolonization by bird species, as wet-meadow areas are the preferred nesting habitat of several species, including the swamp sparrow, common yellowthroat, marsh wren, sora, and Virginia rail (Weller and spatcher 1965, Kantrud and stewart 1984. The establishment of wet-meadow zones in restored wetlands may require initial seeding or transplanting by wetland managers (Galatowitsch 1993), and may be necessary to further increase their use by breeding bird species.…”

Breeding bird communities of recently restored and natural prairie potholes

“…In the 1980s, 200 however, prairie pothole restoration on private land increased markedly due to the Conservation Reserve Program (CRP) and the North American Waterfowl Management Plan (Madsen 1988). Between 1987 and1991, about 1,892 prairie potholes in northern Iowa, southern and central Minnesota, and southeastern South Dakota were restored (Galatowitsch 1993).…”