Fall of giants: European diversity resistance to waterscape degradation and its potential continental drivers

Aquatic landscapes, or waterscapes, face severe threats from human activities propelling their deterioration. Waterscape degradation represents a main driver of the current diversity crisis, although its long-term consequences are difficult to quantify. In addition, the understanding of the potential effects of waterscape degradation on biodiversity at large spatial scales, such as biomes and continents, remains limited. In this work, we explore the potential trends in diversity decay in response to waterscape degradation across Europe to provide a first answer to these main threads. We reconstructed the European waterscape based on available satellite data and simulated diversity patterns using a coalescent metacommunity model run for several European ecoregions and considering nine dispersal abilities. Subsequently, we generated a gradient of waterscape degradation by systematically removing a percentage of available habitat and recalculating diversity metrics. For each ecoregion, dispersal ability, and degradation level we obtained a theoretical gamma diversity value. We synthesized the captured diversity decay trends in two parameters: the proportional decay rate and the collapsing rate, which respectively inform about the speed of diversity loss and its acceleration as waterscape degradation progresses. Finally, we mapped these parameters across Europe and related them with ecoregion structural descriptors (i.e. geographic location, water cover, connectivity, and size). Through this exercise, we could identify ecoregions sensitivities and their continental variation based on their diversity decay parameters. Connectivity and water cover emerged as primary descriptors of diversity decay, with more heterogeneous ecoregions generally exhibiting greater resistance to waterscape degradation. Our study provides a first order approximation to an urgently needed information: the continental-scale consequences of waterscape degradation for biodiversity. This data has the potential to improve conservation practices and facilitate the integration of innovative approaches in management, thereby enhancing our understanding of the consequences posed by one of the principal threats to freshwater diversity. ### Competing Interest Statement The authors have declared no competing interest.