Ecological Indicators : Integrating and extending ecological river assessment: Concept andtest with two restoration projects

While the number of river restoration projects is increasing, studies on their success or failure relativeto expectations are still rare. Only a few decision support methodologies and integrative methods forevaluating the ecological status of rivers are used in river restoration projects, thereby limiting informedmanagement decisions in restoration planning as well’as success control. Moreover, studies quantifyingriver restoration effects are often based on the assessment of a single organism group, and the effects onterrestrial communities are often neglected. In addition, potential effects of water quality or hydrologicaldegradation are often not considered for the evaluation of restoration projects.We used multi-attribute value theory to re-formulate an existing river assessment protocol’and extendit to a more comprehensive, integrated ecological’assessment program. We considered habitat conditions,water quality regarding nutrients, micropollutants and heavy metals, and five instream and terrestrialorganism groups (fish, benthic invertebrates, aquatic vegetation, ground beetles and riparian vegetation).The physical, chemical’and biological states of the rivers were assessed separately and combined to valuethe overall ecological state.The assessment procedure was then applied to restored and unrestored sites at two Swiss rivers to testits feasibility in quantifying the effect of river restoration. Uncertainty in observations was taken intoaccount and propagated through the assessment framework to evaluate the significance of differencesbetween the ecological states of restored and unrestored reaches. In the restored sites, we measured ahigher width variability of the river, as well’as a higher width of the riparian zone and a higher richnessof organism groups. According to the ecological’assessment, the river morphology and the biologicalstates were significantly better at the restored sites, with the largest differences detected for groundbeetles and fish communities, followed by benthic invertebrates and riparian vegetation. The state of theaquatic vegetation was slightly lower at the restored sites. According to our assessment, the presence ofinvasive plant species counteracted the potential ecological gain. Water quality could be a causal factorcontributing to the absence of larger improvements.Overall, we found significantly better biological’and physical states, and integrated ecological statesat the restored sites. Even in the absence of comprehensive before-after data, based on the similarityof the reaches before restoration and mechanistic biological knowledge, this can be safely interpretedas a causal consequence of restoration. An integrative perspective across aquatic and riparian organismgroups was important to assess the biological effects, because organism groups responded differently torestoration. In addition, the potential deteriorating effect of water quality demonstrates the importanceof integrated planning for the reduction of morphological, water quality and hydrological degradation.

  • Genre de document : Revue
  • Type de document : À préciser

  • Auteurs principaux : PAILLEX A., SCHUWIRTH N., LORENZ A. W.
  • Editeur : Elsevier
  • Année de publication : 2017