River floodplains are among the most threatened ecosystems of the world and their protection and restoration is of key importance for river managers. In Europe, the Water Framework Directive (WFD) and the Habitats and Birds Directives (HBDs) provide a guideline for decision processes in floodplain restoration projects. While the WFD, however, represents an aggregated, multiple-species approach aiming at the restoration of the natural hydrological dynamics, the single-species focused HBDs regulate the protection of the existing fauna and flora with protection status. Thus, trade-offs between rheophilic and stagnophilic aquatic organisms may hamper the definition of a compromise solution between the ecological objectives of the restoration. We present an assessment scheme for the restoration of a degraded Danube floodplain near Vienna, which equally considers both WFD and HBDs objectives in a transparent, comprehensible, and objective way. In a first step, predictive hydrological and ecological models were generated for different hydrological scenarios considering the aquatic community composition (floodplain index according to WFD) as well as individual protected species of the taxonomic groups fish, amphibians, reptiles, and water birds (HBDs). Based on these models, we developed an assessment scheme which considered potential changes in the available habitats, the current conservation states, and priorities of the species. Thereby, we included experiences from other restoration projects. The results show that both the multiple-species and the single-species approach achieved a similar ranking of the hydrological scenarios, in which the “business-as-usual” alternative without any restoration measure was identified as the worst case. The multiple-species approach of the floodplain index provided a clear ranking of the hydrological scenarios and revealed a low potential of any target measure to restore the pre-regulation state of the floodplain. In contrast, the single-species approach required a much higher degree of decisions by experts, but provided a detailed insight into spatial effects of the measures on different species, thus revealing the potential for local compensation measures. Our study demonstrates that a combination of these two approaches can be an effective tool for river managers in the development of sustainable floodplain restoration schemes in accordance with the WFD, the HBDs, and national nature protection laws (in this case, the Nature Conservation Acts of Vienna and Lower Austria).

中文翻译：

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将 EC 水框架指令和 EC 栖息地指令的冲突目标整合到洪泛区恢复计划中

河流泛滥平原是世界上受威胁最严重的生态系统之一，其保护和恢复对河流管理者来说至关重要。在欧洲，水框架指令 (WFD) 和栖息地和鸟类指令 (HBD) 为洪泛区恢复项目的决策过程提供了指南。然而，虽然 WFD 代表了一种旨在恢复自然水文动力学的聚合、多物种方法，但以单一物种为重点的 HBD 规范了对现有动植物群的保护，并处于保护状态。因此，嗜流性和嗜滞性水生生物之间的权衡可能会妨碍恢复生态目标之间折衷解决方案的定义。我们提出了一个用于恢复维也纳附近退化的多瑙河漫滩的评估方案，它以透明、可理解和客观的方式同等地考虑 WFD 和 HBD 目标。第一步，考虑到水生群落组成（根据 WFD 的洪泛区指数）以及鱼类、两栖动物、爬行动物和水鸟 (HBD) 分类群的个别受保护物种，为不同的水文情景生成了预测性水文和生态模型. 基于这些模型，我们制定了一个评估计划，该计划考虑了可用栖息地的潜在变化、当前的保护状态和物种的优先级。因此，我们纳入了其他修复项目的经验。结果表明，多物种和单物种方法都实现了相似的水文情景排名，其中没有任何恢复措施的“一切照旧”替代方案被确定为最坏的情况。洪泛区指数的多物种方法提供了对水文情景的清晰排序，并揭示了恢复洪泛区预调节状态的任何目标措施的潜力很低。相比之下，单一物种方法需要专家做出更高程度的决策，但提供了对不同物种措施的空间影响的详细洞察，从而揭示了当地补偿措施的潜力。我们的研究表明，这两种方法的结合可以成为河流管理者根据 WFD、HBD 和国家自然保护法制定可持续洪泛区恢复计划的有效工具（在这种情况下，