Road density simplifies regional food webs

Roads stands as major threats to biodiversity, affecting the functioning of ecosystems and their provision of ecosystem services. Understanding how road-related impacts affect the dynamics of ecological interactions is essential to help manage human impacts on biodiversity, but such studies remain largely unexplored. We investigated the intricate relationship between roads, species vulnerability to road density, and the ensuing effects on food webs across Europe. Utilizing species-specific road density thresholds and trophic interaction data, we constructed regional food webs to assess the potential loss of trophic interactions due to roadkill. Our analysis, encompassing 551 species across three trophic levels, revealed spatially varied impacts, with areas surrounding major cities facing drastic losses of trophic interaction exceeding 90%. Notably, 191 species may be affected by trophic interaction losses (loss of prey or predator). Apex predators exhibited lower direct impacts from road density, while basal-level species seem to be more exposed to direct road-related effects, potentially triggering a cascade of interaction disruptions. Our findings emphasize the need for informed road infrastructure development and targeted conservation strategies to mitigate the negative impacts of roads and traffic, thereby preserving the integrity of ecological networks. This research offers valuable insights for policymakers and conservation practitioners globally by identifying critical areas where road-induced cascade effects may be most pronounced and highlighting trophic groups of species that may be at higher risk.