Habitat benefits can reach downstream

Posted on March 26, 2010

There is widespread agreement that river restoration projects need to take account of catchment-level influences (e.g., discharge variation, water quality, sediment inputs) as well as the environmental and ecological features at the restoration site itself.  However, it can be argued that such a dual level approach is still inadequate because it ignores the ecological influences of adjacent reaches upstream and downstream of the restoration area.  Working on small highland streams, German researchers used correlation analysis to assess influences at three scales (sampling site, adjacent reaches and catchment) on local ecological quality, as indicated by invertebrate sampling.  Morphological features of the stream bed, stream banks and floodplain, including riparian vegetation and woody debris, were used as a proxy for the ecological status of upstream and downstream reaches.  Significant correlations were found at all three spatial scales.  The importance of upstream reaches was similar to that of local habitat quality, and was greatest for reaches within 2.5 km of the sampling site.  Downstream reaches were not influential.  The results suggest that the ecology of degraded reaches (e.g. in urban settings) could benefit from restoration work in more rural  upstream reaches, where land-use pressures are lower and the potential for habitat stream restoration is higher.

Reference:  Kail, J. & Hering, D.  2009.  The influence of adjacent stream reaches on the local ecological status of central European mountain streams.  River Research and Applications 25, 537-550.