An assessment of long-term compliance with performance standards in compensatory mitigation wetlands

Published source details van den Bosch K. & Matthews J.W. (2017) An assessment of long-term compliance with performance standards in compensatory mitigation wetlands. Environmental Management, 59, 546-556.
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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
	Restore/create freshwater marshes or swamps (specific action unclear) Action Link

Require mitigation of impacts to marshes or swamps

A study in 1996–2012 of 30 compensatory mitigation sites in Illinois, USA (van den Bosch & Matthews 2017) reported that that they did not consistently meet targets specified in permits after 4–21 years. Of the 30 mitigation sites, 29 were classified as wetlands based on vegetation, water levels and soils. However, of seven targets related to vegetation, only one (cover of wetland plants) was met in 100% of applicable sites at some point during monitoring. The other targets were met in 13–86% of applicable sites at some point during monitoring. The study does not report the precise target for each site. The study also compared vegetation in compensatory sites and remnant natural wetlands – see Action: Restore/create marshes or swamps (specific intervention unclear). Methods: The study involved 30 sites where wetland restoration was required by permits for road construction and maintenance. Target wetlands were marshes (15 sites), swamps (13 sites) or a mixture of both (2 sites). Restoration was carried out between 1992 and 2004. Vegetation was surveyed once/site in 1996–2009 and once/site in 2012.

(Summarised by: Nigel Taylor)
Restore/create freshwater marshes or swamps (specific action unclear)

A replicated, paired, site comparison study in 1996–2012 involving 15 wetland restoration sites in Illinois, USA (van den Bosch & Matthews 2017) found that they had higher or lower quality vegetation than nearby natural wetlands, depending on the metric. The 15 restoration sites had lower quality vegetation than 15 nearby natural wetlands when measured as a conservatism score (how characteristic the plant species are of undisturbed local habitats), but higher quality vegetation when measured a floristic quality index (combining conservatism score with species richness). The proportion of native, non-weedy, perennial species was statistically similar in the restoration sites (49–55% of species) and the natural wetlands (60% of species). Methods: The study involved 15 sites restored between 1992 and 2004 (methods not reported) and a natural wetland site near each restored site. The study included both marshes and swamps (number of each not clearly reported). Vegetation was surveyed twice in restoration sites (once in 1996–2009, once in 2012) and once in natural wetlands (2012).

(Summarised by: Nigel Taylor)