Functional assessment of five wetlands constructed to mitigate wetland loss in Ohio, USA

  • Published source details Wilson R.F. & Mitsch W.J. (1996) Functional assessment of five wetlands constructed to mitigate wetland loss in Ohio, USA. Wetlands, 16, 436-451.


This study is summarised as evidence for the following.

Action Category

Require mitigation of impacts to marshes or swamps

Action Link
Marsh and Swamp Conservation

Restore/create freshwater marshes or swamps (specific action unclear)

Action Link
Marsh and Swamp Conservation
  1. Require mitigation of impacts to marshes or swamps

    A study in the late 1980s/early 1990s in Ohio, USA (Wilson & Mitsch 1996) reported that five development permits that demanded compensation for impacts to marshes and swamps did not maintain their area, number or vegetation type. The permits required creation of 42 ha of marsh/swamp in five sites, compared to 24 ha lost to development in five sites. All five permits were followed through, but only restored/created 16 ha of marsh/swamp: a net loss of 8 ha. Further, compensation was not “in kind” in two of the five sites: one failed to establish woody vegetation that was present in a lost swamp, and one created a deep pond surrounded by trees on upland (rather than a marsh). The study also quantified the vegetation of created sites in more detail – see Action: Restore/create marshes or swamps (specific intervention unclear). Methods: This study analyzed data relating to five permits, issued in the late 1980s/early 1990s for projects involving filling of marshes or swamps. Permits were issued under Section 404 of the Clean Water Act. The assessment was based on available published reports and field surveys carried out 1–4 years after restoration/creation was completed.

    (Summarised by: Nigel Taylor)

  2. Restore/create freshwater marshes or swamps (specific action unclear)

    A replicated study in 1994 of five freshwater wetland restoration/creation sites in Ohio, USA (Wilson & Mitsch 1996) reported that four of the sites contained the desired emergent vegetation within four years, and that wetland-characteristic species made up at least 45% of the vegetation cover in each site. Restoration/creation was intended to replace areas of emergent wetland vegetation. After approximately 1–4 years, four of five sites did contain emergent wetland vegetation (other site: submerged vegetation surrounded by upland). Across all sites, wetland areas contained 4–52 plant species (excluding “unidentified grasses”). Wetland species made up 65­–100% of vegetation cover. Wetland-characteristic species made up 45­–100% of vegetation cover. For data on the absolute cover of individual plant species, see original paper. Methods: In 1994, vegetation was surveyed in 0.25-m2 quadrats (number not clear) in five wetland restoration/creation sites. The sites were approximately 1–4 years old. Interventions were not clearly reported by included excavation, rewetting or other management of water inputs and outputs, planting herbs, planting trees/shrubs, and invasive species removal. Surveys included emergent, floating and submerged vegetation in wetland habitats only, and where water was <1 m deep.

    (Summarised by: Nigel Taylor)

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