200 years of river engineering: changes in meta-ecosystem resilience and connectivity

This study investigates changes in habitat connectivity and meta-ecosystem resilience between 1817 and 2022 along a 150 km section of a large European river (Danube) and its adjacent floodplains. The analysis was based on a time series of functional habitat networks (graphs) constructed from historical records and remote sensing data, integrating habitat suitability and dispersal modes of functional organism groups. The results indicate that overall habitat availability declined by about 50% since 1817, leading to the near-complete loss of functional connectivity among dynamic habitats by 1910. Less dynamic habitats persisted or expanded but became functionally less connected. Connectivity-based habitat classification further revealed four distinct functional connectivity clusters and the near-complete loss of an originally dominant, dynamic, and highly connected habitat type. Furthermore, the results indicated a fundamental loss of meta-ecosystem resilience. This development was reflected by increased spatial modularity among functionally similar habitats and by reduced layer dissimilarity and structural robustness in multilayer networks representing the spatial habitat structure and functional habitat connectivity across different functional organism groups. SignificanceRiver engineering is widely recognized for causing habitat loss and fragmentation, yet its long-term consequences for functional habitat connectivity and meta-ecosystem resilience remain poorly understood. This study illustrates how 200 years of river engineering reorganized a vast, dynamic, and highly interconnected river-floodplain system into a fragmented and functionally homogenized state. The findings empirically expose the true scale of functional degradation, offering a vital and novel historical perspective that underscores the urgent need for large-scale, process-based restoration.