Summary1. Hydromorphological river restoration usually leads to habitat diversification, but the effects on benthic invertebrates, which are frequently used to assess river ecological status, are minor. We compared the effects of river restoration on morphology and benthic invertebrates by investigating 26 pairs of non-restored and restored sections of rivers in Austria, Czech Republic, Germany, Italy and the Netherlands. 2. Sites were grouped according to (1) region: central Europe vs. southern Europe; (2) river type: mountain vs. lowland rivers; (3) restoration approach: active vs. passive restoration and (4) a combination of these parameters. All sites were sampled according to the same field protocol comprising hydromorphological surveys of river and floodplain mesohabitats, microhabitats at the river bottom and habitat-specific sampling of benthic invertebrates. Restoration effects were compared using Shannon-Wiener Indices (SWIs) of mesohabitats, microhabitats and invertebrate communities. Differences in metric values between non-restored and restored sites were compared for 16 metrics that evaluated hydromorphology and the benthic invertebrate community. 3. Mean SWIs differed for both mesohabitats (1AE1 non-restored, 1AE7 restored) and microhabitats (1AE0 non-restored, 1AE3 restored), while SWIs for invertebrate communities were not significantly different (2AE4 non-restored, 2AE3 restored). Meso-and microhabitat metrics in the restored sections were usually higher compared with the non-restored sections, but the effects on invertebrate metrics were negligible. 4. Measures in southern Europe and mountainous regions yielded larger differences between non-restored and restored sections of rivers. Differences in the meso-and microhabitat metrics were largest for actively restored sections of central European mountain rivers and rivers from southern Europe, followed by passively restored mountain rivers in central Europe. The smallest differences were observed for lowland sites. There was no significant restoration effect on invertebrate metrics in any categories. 5. Synthesis and applications. Restoration measures addressing relatively short river sections (several hundred metres) are successful in terms of improving habitat diversity of the river and its floodplain. Active restoration measures are suitable if short-term changes in hydromorphology are desired. To realize changes in benthic invertebrate community composition, habitat restoration within a small stretch is generally not sufficient. We conclude that restoring habitat on a larger scale, using more comprehensive measures and tackling catchment-wide problems (e.g. water quality, source populations) are required for a recovery of the invertebrate community.
1. Restoration of river hydromorphology often has limited detected effects on river biota. One frequently discussed reason is that the restored river length is insufficient to allow populations to develop and give the room for geomorphological processes to occur. 2. We investigated ten pairs of restored river sections of which one was a large project involving a long, intensively restored river section and one represented a smaller restoration effort. The restoration effect was quantified by comparing each restored river section to an upstream nonrestored section. We sampled the following response variables: habitat composition in the river and its floodplain, three aquatic organism groups (aquatic macrophytes, benthic invertebrates and fish), two floodplain-inhabiting organism groups (floodplain vegetation, ground beetles), as well as food web composition and land-water interactions reflected by stable isotopes. 3. For each response variable, we compared the difference in dissimilarity of the restored and nearby non-restored section between the larger and the smaller restoration projects. In a second step, we regrouped the pairs and compared restored sections with large changes in substrate composition to those with small changes. 4. When comparing all restored to all non-restored sections, ground beetles were most strongly responding to restoration, followed by fish, floodplain vegetation, benthic invertebrates and aquatic macrophytes. Aquatic habitats and stable isotope signatures responded less strongly. 5.When grouping the restored sections by project size, there was no difference in the response to restoration between the projects targeting long and short river sections with regard to any of the measured response variables except nitrogen isotopic composition. In contrast, when grouping the restored sections by substrate composition, the responses of fish, benthic invertebrates, aquatic macrophytes, floodplain vegetation and nitrogen isotopic composition were greater in sections with larger changes in substrate composition as compared to those with smaller changes. 6. Synthesis and applications. The effects of hydromorphological restoration measures on aquatic and floodplain biota strongly depend on the creation of habitat for aquatic organisms, which were limited or not present prior to restoration. These positive effects on habitats are not necessarily related to the restored river length. Therefore, we recommend a focus on habitat enhancement in river restoration projects.
35The success of river restoration was estimated using the ecosystem services approach. In eight pairs of restored-unrestored reaches and floodplains across Europe, we quantified provisioning (agricultural products, wood, reed for thatching, infiltrated drinking water), regulating (flooding and drainage, nutrient retention, carbon sequestration) and cultural (recreational hunting and 40 fishing, kayaking, biodiversity conservation, appreciation of scenic landscapes) services for separate habitats within each reach, and summed these to annual economic value normalised per reach area. We used locally available data and literature, did surveys among inhabitants and visitors, and used a range of economic methods (market value, shadow price, replacement cost, avoided damage, willingness-to-pay survey, choice experiment) to provide final monetary service 45 estimates. Total ecosystem service value was significantly increased in the restored reaches (difference 1400 ± 600 € ha -1 y -1 (2500 minus 1100, p=0.03, paired t-test). Removal of one extreme case did not affect this outcome. We analysed the relation between services delivered and with floodplain and catchment characteristics after reducing these 23 variables to four principal components explaining 80% of the variance. Cultural and regulating services correlated positively 50 with human population density, cattle density and agricultural N surplus in the catchment, but not with the fraction of arable land or forest, floodplain slope, mean river discharge, or GDP. Our interpretation is that landscape appreciation and flood risk alleviation are a function of human population density, but not wealth, in areas where dairy farming is the prime form of agriculture. 55 225
STAR is a European
In this special issue we present the major results of the EU funded research project STAR (Standardisation of River Classifications: Framework method for calibrating different biological survey results against ecological quality classifications to be developed for the Water Framework Directive; contract number EVK1-CT-2001-00089).The aims of STAR were to develop methodologies, tools and background information to assess rivers throughout Europe using diatoms, macrophytes, invertebrates, fish and hydromorphological features. The project's research questions and structure are described in detail by Furse et al. (2006). STAR has generated results over a wide spectrum of topics, ranging from river typologies and new methodologies for assessing the condition of rivers using macrophytes to the uncertainty of assessment approaches. This special issue is structured to reflect the broad scope of the project and is sub-divided into seven sections. Each contains up to six papers describing specific results and each is introduced by a summary paper reviewing the main findings of the papers in the section. Individually, these sections are:-Stream and river typologies -Linking organism groups -Macrophytes and diatoms -Hydromorphology -Tools for assessing European streams with macroinvertebrates -Intercalibration and comparison -Errors and uncertainty in bio-assessment methods Acknowledgements
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