Can artificial waterways provide a refuge for fioodplain biodiversity? A case study from North Western Germany

Rivers and floodplains are among the most species-rich ecosystems in Middle Europe. Intensive anthropogenic influence has led to a loss of floodplain area and threatens their ecological functionality. This is especially the case for waterways, which have been subject to river engineering due to their economic importance and thus have lost a significant amount of their original floodplains and biodiversity. Canals as artificial waterways have been in the focus of reconciliation ecology, and they have been proven to serve as a refuge for several aquatic species groups where their original habitat is impaired or lost. However, the potential to preserve terrestrial macrophytes and biodiversity along their banks has rarely been considered. Thus the question arises whether canals can provide, at least partly, suitable habitat space to sustain species diversity and functionality of floodplains. In the present case study, we compared the floristic, functional and structural diversity of the floodplain and the respective adjacent areas of the river Ems and the Dortmund-Ems canal in North Western Germany, since both waterways run in parallel and are hydrologically connected. Species composition shows distinct differences between both waterways. Most species along the canal are mainly generalists adapted to anthropogenic influence, while species along the river are characteristic for floodplain systems. Species diversity is up to 10% higher along the canal due to higher lateral heterogeneity, while functional divergence and landscape structure diversity are up to 5% higher along the natural river. Diversity distribution patterns are mainly influenced by landscape structure and land use patterns. Numbers of endangered species did not differ significantly. Thus, the canal can serve as a habitat for single endangered floodplain species but it cannot substitute the functions of a natural dynamic floodplain. Increasing structural diversity and preserving the habitat function of the canal banks by an adapted management regime might enhance the ecological value of a heavily used artificial waterway within the given economic limitations. (C) 2014 Elsevier B.V. All rights reserved.