International Review of Hydrobiology最新文献

The progressive loss of biodiversity in rivers and their floodplains has not yet been stopped. With the European Biodiversity Strategy and the goal of restoring at least 25,000 km of free-flowing European rivers by 2030, the first important step has been taken. Now we need to be able to effectively demonstrate a reversal of biodiversity loss as well as the success of urgently needed restoration measures. This special issue presents twelve results of current river and floodplain restoration and evaluation approaches that have successfully combined hydromorphological restoration measures with interdisciplinary research. We report comprehensively on the challenges and opportunities that river and floodplain restoration can offer to protect the biodiversity and ecosystem functioning of these habitats.

Within the EU LIFE-Nature project ‘River and floodplain revitalisation Emmericher Ward’, three small temporary waters and a former gravel pit were connected by a side channel running parallel to the river Rhine through former groyne fields. The initial status of macrozoobenthos, fish, avifauna, flora, vegetation, and habitats before and their development after implementation of the project's measures were recorded and compared. The monitoring years 2018 and 2019 were exceptionally dry and accompanied by an extremely low runoff in the Rhine and the side channel. These conditions likely affected the development of habitats and species populations in the new side channel. The new side channel showed intensive morphodynamic development and differentiation of its structures. While the more complex vegetation and habitat types appeared as mostly species-poor initial stages, short-lived species-rich pioneer habitats such as annual mud banks in the water exchange area were already established. Two years after the implementation, the benthic invertebrate fauna was still predominantly species-poor and dominated by neozoans. Occasionally, representatives of the more sensitive EPT fauna (Ephemeroptera, Plecoptera, Trichoptera) were already detected but were, in general, strongly underrepresented in the main stream. Low colonisation potential, nonpermanent flow, and lack of river wood limit the development of the macrozoobenthos community. The relative abundance of rheophilic fish species increased in the project area and high juvenile fish densities proved the function as a nursery habitat. As pioneer species of riverine landscapes, sand martins and little ringed plovers colonised the new structures already in the first year. The initial state of the side channel represented a typical dynamic pioneer habitat pattern of a sandy lowland river, which was almost absent in the Lower Rhine area. The new habitats were quickly colonised by pioneer flora and fauna, but the potential for more demanding and complex communities was restricted by the poor structural and biological states of the Lower Rhine.

The majority of rivers in Europe has been dramatically altered in terms of their morphology and hydrology with severe consequences for the diversity and ecological functioning of the rivers and their floodplains. Consequently, an increasing number of river reaches has been restored over the past decades, often including the removal of bank fixation to reinitiate bank erosion and allowing for a rewidening of the rivers' cross-section. However, monitoring in detail the effect of such a measure on riverine vegetation is scarce. Using a Before-After-Control-Impact (BACI) design, we analysed the early changes of the vegetation 2 years after the removal of bank fixation at the Mulde River (central Germany). The results were compared with two types of control sites, representing a nonrestored as well as a natural riverbank that has never been fixed. We analysed differences in taxonomic and functional composition of the vegetation between bank types as well as community turnover after restoration. Two years after restoration, the vegetation differed clearly from the nonrestored sites. A substantial proportion of the community, especially the newly established species, became more similar to the natural bank community. Most importantly, spatiotemporal heterogeneity of the vegetation increased after removal of bank fixation, being an indicator for re-established dynamic processes similar to the natural site. The presented data serve as a baseline for a long-term monitoring and quantitative meta-analysis of restoration effects.

Over the last 40 years, a growing number of restoration projects have been implemented to improve the ecological conditions of highly degraded rivers and their floodplains. Despite considerable investment in these projects, information is still limited about the effectiveness and the success of such river restoration measures, mainly due to a lack of standardised and interdisciplinary assessment approaches. During the project ‘Wilde Mulde—Restoration of a dynamic riverine landscape in Central Germany’, we implemented hydromorphological restoration measures (installation of large wood, removal of rip-rap, reconnection of a former river side-arm) along a lowland river in Central Germany. We carried out intensive scientific monitoring of biodiversity, hydromorphology, ecosystem functions and services, as well as socio-economic aspects. A Before/After-Control/Impact (BACI) design was used to identify the spatial and temporal effects of the restoration measures and to distinguish them from changes caused by background variation. For this, we used a comprehensive set of indicators, including abiotic (flow velocity, diversity of riverbed topography, and flow resistance), biological (ecosystem respiration, macroinvertebrates, fish, carabids, vegetation, and birds) and socio-economic (acceptance and public awareness) indicators as well as the ecosystem service indicator aesthetic quality of the landscape. To meet the inherent challenges of such a large-scale field experiment, like unpredictable environmental conditions, we used an experimental approach that allowed us to demonstrate a measurable success of the implemented restoration measures. The majority of the abiotic and some of the biological and socio-economic indicators at the restored sites approached values of a natural reference site while already deviating from values of a nonnatural reference site two years after restoration. In addition to the applied interdisciplinary approach, multiple scales of field investigations and data analyses are essential as key components for evaluating successful river and floodplain restoration projects.

The concept of ecosystem services (ES) is a powerful tool for communicating with stakeholders because it highlights the benefits of ecosystems for people and demonstrates their economic importance through monetized values. However, this hypothesis has rarely been substantiated in the context of local landscape planning. To investigate which ecosystem services information formats (ESIF) stakeholders prefer in decision situations, we experimented with a highly conflictual planning situation about the Lower Mulde restoration in Germany. We invited local stakeholders to a so-called ‘future vision workshop’. It included a paper-based, noncompetitive planning game, which combined the freedom of choice with strict rules for justifying the proposed measures. We tested how often participants used different ESIFs to justify their decisions, focusing on quantification, monetization, and the default qualitative (ordinal-scaled) format applied in landscape planning. A total of 17 representatives from stakeholder groups such as nature conservation, recreation, and local politics attended. We provided information on four ES and eight related measure proposals to the stakeholders, who used them to select, locate, and justify actions for the area's future development. The participants applied the ordinal-qualitative format in more than two-thirds of the decisions. Quantification and monetization were used with approximately equal frequency, mostly for measures that favoured flood risk regulation. Actions supporting habitat provision and biodiversity were justified exclusively in ordinal-qualitative terms. Instead of our provided quantifications, some participants mentioned numbers they were already familiar with before. They also partly doubted our monetization approaches. In conclusion, we recommend combined and context-specific uses of several ESIFs, while using the ordinal-qualitative format as the basis. Furthermore, the participants appreciated the workshop and requested that the results be presented to the city council. The workshop also confirmed that the ES concept is challenging to understand, especially for laypeople unfamiliar with ES and landscape planning.