Author(s): R. Schinegger; A. Melcher; C. Trautwein; S. Schmutz
Linked Author(s):
Keywords: Multi-impacted rivers; European scale; Ecological status; Pressure in-dex
Abstract: Most European rivers are affected by different types of human pressures that may impair fish populations. We analysed 15 pressure variables of 4 different pressure groups, i.e. hydrology, morphology, water quality and connectivity to detect spatial patterns, relationships and interactions between pressures and natural environment at the European scale. Based on literature, national databases and expert knowledge important pressures were identified and collected within the EUproject EFI+ in 14 countries at about 10 000 fish-sampling sites in Europe. In 90% of the catchments analysed fish migration was interrupted by barriers. We used PCA and correlation analysis to identify key pressures and to eliminate redundant pressures at local and river segment scale. Thirteen variables were found to describe the majority of human degradation at a specific site. To aggregate into pressure type specific indices we first harmonized the variables along a gradient from1-5, i.e. from nearly undisturbed to strongly impacted sites. Further, we calculated the mean of values > class 2 only, to avoid that values 2, i.e. to better indicate degradation. Pressure analysis showed that 24% of sites are affected by single, 22% by double 19% by triple and 12% by four pressure groups. Only 23% of sites are less affected, i.e. class <=2. In terms of pressure types, analysed sites showed alterations in 55% for water quality pressures, 40% for hydrology, 37% for morphology and 34% for connectivity (river segment). In 45% of the cases water quality problems are also associated with other pressures. The results clearly show that European rivers are multi-impacted. Therefore, only restoration strategies simultaneously considering all important types of pressures will guarantee the achievement of the good ecological status or potential sensu EU Water Framework Directive.
Year: 2009