An Ecological Assessment of Wetland Mitigation Projects in East Tennessee

Federal wetland protection regulations stipulate that developers who destroy natural wetlands are required to construct mitigation or replacement wetlands. Despite the frequency of wetland mitigation, few studies have evaluated the ability of mitigated wetlands to mimic the ecological function and community composition of natural wetlands. Fewer still compare mitigation sites with existing natural wetlands in the same ecological region.

Studies from other freshwater habitats suggest that comparisons of the ratios of functional feeding groups (FFGs) of benthic macroinvertebrates (i.e., shredders, scrapers, collectors, predators) may provide useful information about the ability of mitigated wetlands to mimic the ecological functions of natural wetlands.

In this study I examined the ratios of FFGs of benthic macroinvertebrates in three mitigated wetlands and in a natural reference wetland in the Ridge and Valley physiographic province of the southeastern United States. Using a multihabitat sampling protocol, I sampled open water areas, Typha latifolia zones, and areas of mixed emergent vegetation < 1 m in height. Chi-square tests indicate that the ratios of FFGs in the mitigated wetlands are significantly different than those of the natural wetlands. Based on these results, I conclude that the mitigated wetlands have a much different trophic structure than the natural wetland, and thus do not replace the ecological function of natural wetlands lost to development. The results from this study raise questions about the long-term viability of these systems and the use of wetland mitigation as a natural resource management strategy.

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