Citation:

Griffith, M. AND M. McManus. Consideration of spatial and temporal scales in stream restorations and biotic monitoring to assess restoration outcomes: A literature review, part 2. River Research and Applications. John Wiley & Sons Incorporated, New York, NY, 36(8):1398-1415, (2020).

Impact/Purpose:

This paper addresses Safe and Sustainable Water Resources research on the consideration of scale in matching environmental stressors and their sources, restoration, and recovery in streams (SSWR 3.01C.2). We find that in some cases untreated stressors may influence the outcomes of the restoration, but in many cases, there are mismatches in the temporal or spatial scale of the restoration. For example, either biomonitoring was conducted in too short a time for effects to be observed or the sources and stressors needing remediation occurred at a larger catchment scale when the restoration was conducted only at the reach scale. The results inform ongoing efforts to support local restorations of streams at scales from stream channels to watersheds by assessing the relationship between the scale of a restoration and the success of the restoration as measured by improvements in the biotic assemblages or their ecosystem function.

Description:

Stream and river restoration practices have become common in many parts of the world. To answer the question whether such restoration measures improve freshwater biotic assemblages or functions over time, and if not, can general reasons be identified for such outcomes, we conducted a literature survey and review of studies in which different types of stream restorations were conducted and outcomes assessed. In the first paper, we reviewed studies of culvert restorations, acid mine drainage or industrial pollution restoration; and urban stream restoration projects. Here, we review studies of restoration via dam removal, changes in dam operation or fish passage structures; instream habitat modification; riparian restoration or woody material addition; channel restoration and multiple restoration measures and develop some general conclusions from these reviews. Biomonitoring in different studies detected improvements for some restoration measures; other studies found minimal or no statistically significant increases in biotic assemblage richness, abundances or functions. In some cases, untreated stressors may have influenced the outcomes of the restoration, but in many cases, there were mismatches in the temporal or spatial scale of the restoration measure undertaken and associated monitoring. For example, either biomonitoring to measure restoration effects was conducted over a too short a time period after restoration for effects to be observed, or the sources and stressors needing remediation occurred at a larger catchment scale than the restoration. Also, many restoration measures lack observations from unimpaired reference sites for use in predicting how much of a beneficial effect might be expected.

Record Details: