Using benthic macroinvertebrates to evaluate the effectiveness of stream restoration for improving biological integrity
PI(s): Voshell, Jr, J Reese
Investigators: Hudy, Mark, Braccia, Amy, Willey, Tara
Abstract: Billions of dollars are being spent on stream restoration but the results of these expenditures are unknown, especially in regard to recovery of biological communities, because appropriate post-restoration studies rarely occur. We are addressing this issue by first conducting detailed baseline studies of the benthic macroinvertebrate assemblages in relation to a wide array of environmental variables in an impaired stream where a restoration program has been implemented. Then, the same stream will be studied over a long time frame (at least 5 years) to follow the recovery of biological integrity and explain how these changes are related to stream restoration efforts.
Description:
Since 1990, government agencies have spent more than $7.5 billion on river restoration projects in the U.S.; yet, only about 10% of these projects have been monitored for success, especially in regard to recovery of biological integrity. Furthermore, where follow up biological studies have occurred, they are limited in scope, employ overly simple methodology, and are not conducted synchronously with studies of the environmental stressors that were responsible for the degraded condition of the stream. Over the next few decades, even greater resources are to be put into stream restoration activities in the U.S. Agriculture is one of the greatest causes of impaired streams because of the addition of sediment, nutrients, and organic waste from nonpoint sources. In cases of streams impaired by these agriculturally derived nonpoint pollutants, restoration will be attempted through the Total Maximum Daily Load (TMDL) program, which relies on voluntary implementation of best management practices (BMP's) by private landowners. Conservation programs that eliminate agricultural use of land near streams and establish forested riparian buffers by means of cost sharing, such as the Conservation Reserve and Enhancement Program (CREP), are being used to assist private landowners in adopting BMP's.
The underlying assumption of stream restoration programs, such as CREP, is that biological integrity will recover following pollutant reduction. Unfortunately, there is very little scientific evidence to support the assumption that recovery of biological integrity accompanies steam restoration. Agricultural land use adjacent to streams typically impairs multiple, interrelated stream components (water quality, physical habitat, food resources, channel geomorphology) which negatively affect the structure and function of biological assemblages, yet these components are rarely studied with a synchronous, integrated design and over the appropriate length of time (greater than 1 year). As a result, we know much less than we should about whether spending vast sums of money for stream restoration is leading to recovery of biological integrity in degraded streams and, if recovery does happen, when it will be noticeable.
Through the recent studies of cattle grazing impacts (Braccia and Voshell), we have developed sampling procedures that, in combination with advanced statistical techniques, can be used to quantify and link the environmental variables responsible for the benthic macroinvertebrate assemblage observed in impaired streams. (Benthic macroinvertebrates are aquatic insects and their relatives that live on the bottoms of water bodies.) This approach involves intensive quantitative benthic sampling and habitat measurements. We have begun similar studies in a stream that is listed as impaired by the Virginia Department of Environmental Quality, Smith Creek near Harrisonburg, Virginia. This study is an interdisciplinary effort with scientists at James Madison University in order to include expertise in the vast array of environmental variables and ecological processes that exist in streams.
Impact:
This project will help resolve lingering questions about the overall stressor identification component of TMDL plans. Further, our findings will help us understand the ecological processes that lead towards biological recovery of an impaired stream. We cannot rely just on the number of trees planted or number of cattle excluded as metrics of successful stream restoration. If stream restoration is going to be successful from an ecosystem perspective, then instream metrics that accurately measure ecological recovery in relation to restoration activities need to be identified and employed.
Commodities:
Resources: Aquatic Entomology Laboratory
Disciplines: Aquatic Systems, Ecology, Environmental Quality
Audiences: Environmental Groups, Government Agencies, Researchers
