Assessing wetland compensatory mitigation sites to aid in establishing mitigation ratios

Published source details Robb J.T. (2002) Assessing wetland compensatory mitigation sites to aid in establishing mitigation ratios. Wetlands, 22, 435-440.
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This study is summarised as evidence for the following.

	Action	Category
	Require mitigation of impacts to marshes or swamps Action Link

Require mitigation of impacts to marshes or swamps

A study in 1998–1999 in Indiana, USA (Robb 2002) reported that permits requiring compensation for impacts to marshes and swamps did not prevent a loss in marsh/swamp area or maintain habitat types. The study examined 345 sites where marsh/swamp or aquatic habitats should have been restored or created to compensate for loss. Of these sites, 214 had been constructed as planned. In a sample of 31 constructed sites, permits required restoration/creation of 26.3–30.2 ha of marshes/swamps to compensate for impacts to 12.1–12.8 ha. The actual area of marsh/swamp created was 10.2 ha. So, there was a 16–20% net loss of marsh/swamp area in constructed sites. For three of four vegetation types (shrubby swamps, wet meadows, shallow marsh), the area restored/created (6.4 ha) was greater than the area lost (4.1 ha). For forested swamps, the area restored/created (3.8 ha) was less than the area lost (8.0 ha). Methods: The status of 345 compensatory mitigation sites, required by Section 404 permits issued before December 1996, was checked in 1998–1999. Status was classified as constructed, incomplete or no construction attempted. Vegetation of 31 sites was surveyed in more detail.

(Summarised by: Nigel Taylor)