Europe's Ecological Debt: Mapping Freshwater Restoration Needs.

Since the 20th century, global biodiversity indicators declined, especially for freshwater ecosystems. In European Union, to counter this, the enactment of the Habitats Directive (HD) and the Water Framework Directive (WFD) established legally binding environmental objectives for Member States. Thus, identifying where HD and WFD non-compliance occurs is critical, as these locations represent areas of restoration needs for freshwater environments. We used data from the HD (habitats and species) and WFD and harmonised these datasets using River Restoration Units (R2U), preserving river network structure and providing a consistent spatial resolution. Applying the Composite Indicator of Conservation Status to HD habitats, HD species, and WFD Good Ecological Status, we determined the restoration needs for each R2U. This allowed contrasting restoration needs for HD and WFD at European and national scales, and mapping the combined freshwater-related restoration needs. Around 89% and 55% of R2U expressed restoration needs according to habitats and species, respectively. This rose above 93% for the overall HD goals and exceeded 45% for the WFD. Less than 5% of R2U complied with both directives. We found a European-wide gradient of decreasing restoration needs from habitats, to species, and to WFD, though this pattern was inconsistent among Member States. The spatial patterns of restoration needs identified seem to align with socio-economic conditions and land-use patterns across Europe. The European-wide trend suggests a sequential process in which habitat loss and degradation lead to delayed biodiversity impairment, which may result in subsequent impairment of ecosystem functioning. These are consistent with ecological theory, suggesting that habitat degradation may have delayed but potentially cascading effects on biodiversity and ecosystem functioning. The Nature Restoration Regulation (NRR) can potentially halt European ecological degradation, but restoration efforts must be scaled up and coherently implemented. This broad-scope perspective provides actionable guidance to support NRR implementation across multiple governance levels.