You are here:
Meta-Analysis of Lost Ecosystem Attributes in Urban Streams and the Effectiveness of Out-of-Channel Management Practices
Citation:
Smucker, Nathan J. AND Naomi E. Detenbeck. Meta-Analysis of Lost Ecosystem Attributes in Urban Streams and the Effectiveness of Out-of-Channel Management Practices. RESTORATION ECOLOGY. Blackwell Publishing, Malden, MA, 22(6):741-748, (2014).
Impact/Purpose:
Watershed development is a leading cause of stream impairment and increasingly threatens the availability, quality, and sustainability of freshwater resources. Many management practices have been used with the goal of reducing these negative effects of development, but the effectiveness of these practices and their links to downstream ecosystem conditions are poorly documented. Our work synthesized results from numerous studies and quantified the magnitude of development and restoration effects on stream ecosystem structure and function. While management efforts tend to improve the ecological structure and function of streams, these attributes fail to attain conditions found in minimally disturbed reference streams. Our results help inform management priorities and expectations, and they emphasize the importance of implementing mindful development and protective actions in a watershed context.
Description:
Watershed development is a leading cause of stream impairment, and it increasingly threatens the availability, quality, and sustainability of freshwater resources as human populations continue to grow and migrate. Most efforts have focused on trying to improve ecological conditions through in-stream habitat or geomorphic restoration, but growing amounts of research indicate little to no long-term ecological success and that stream management needs to occur in the context of watershed conditions. However, little research has focused on linking out-of-stream management practices to downstream ecosystem conditions. Given the limitations of extrapolating from case-by-case projects and of scarce monitoring data, we conducted a meta-analysis of scientific literature with the intent of explicitly quantifying (1) losses in downstream ecosystem attributes due to watershed development and (2) the effectiveness of out-of-stream management practices intended to restore or protect streams. We calculated response ratios for water quality, habitat/hydrology, ecological structure, and ecological function attributes by comparing restored to degraded (Rt/Dg) streams (or post- and pre-management), restored to reference (Rt/Rf) streams, and degraded to reference streams (Dg/Rf). Ecosystem attributes of streams in developed watersheds were significantly less than those in reference streams (response ratio Dg/Rf < 0, P < 0.01), and ecological structure, ecological function, water quality, and physical habitat attributes were only 23%, 34%, 28%, and 76%, respectively, of those in reference streams. When compared to streams in developed watersheds, management practices significantly improved ecosystem attributes (response ratio Rt/Dg > 0, P < 0.05). Ecological structure, ecological function, water quality, and physical habitat attributes were 148%, 114%, 116%, and 134%, respectively, of those in degraded streams. However, ecosystem attributes at restored sites were significantly less than those at reference sites (response ratios Rt/Rf < 0, P < 0.01), and median response ratios of all attributes in restored streams were 53% of those in reference streams. Results indicated that management practices often improved ecological conditions in degraded streams, but still failed to restore pre-disturbance or reference stream conditions. These trends highlight the need for preventative actions in a watershed context and can inform future management strategies and watershed development practices.
