Differing Effects of Restoration and Habitat Enhancement in Four Southern Appalachian Streams

ABSTRACT

Stream mitigation is widely used to offset and restore anthropogenic stream degradations, yet ecosystem health is not always improved. Specific mitigation type may play a role in the potential for biotic improvement, with differing common mitigation practices including restoration and habitat enhancement. By looking at small factors in stream communities, such as macroinvertebrates, a larger connection can be made to the overall biotic integrity and quality of the aquatic habitat. This study used a Before-After-Control-Impact design to evaluate changes to biotic integrity of four streams in western North Carolina that underwent either complete restoration or habitat enhancement as compensatory mitigation under provisions of the United States Clean Water Act. We developed a Habitat Quality Improvement Index (HQII) to compare macroinvertebrate family-based metrics of habitat quality between 2011 (pre-mitigation) and 2021 (post-mitigation) and used a multivariate analysis to examine changes in macroinvertebrate family composition at each site. Analysis of HQII values using a Monte Carlo resampling procedure showed significant improvement at restored sites, whereas habitat quality declined significantly at sites that underwent habitat enhancement only. Our results indicate that restoration practices can have positive impacts on stream health, especially where habitat degradation is localized, and macroinvertebrate populations at high-quality upstream sections can provide a source for recolonization once habitat conditions improve.