Mapping terrestrial eutrophication across Europe from plant community trophic signatures and reconstructed pre-fertiliser baselines

Reactive nitrogen inputs from fertilisers and combustion have profoundly altered the nitrogen cycle and are a major driver of terrestrial and freshwater eutrophication, with cascading effects on biodiversity and ecosystem services. Despite decades of regulation in Europe, spatially explicit, ecologically meaningful monitoring layers that are consistent across countries remain limited. Here we use the trophic ecological preferences of vascular plant species (Ellenberg-type nutrient indicator values) combined with spatially explicit species observations from GBIF to produce continent-scale maps of trophic status as a proxy for nutrient overload and an indicator of ecosystem response to nutrient enrichment. Spatial segments of a mesotrophic nature dominate the map (58.3%), while oligotrophic units are largely confined to mountainous, forested and heathland regions (32.8%) and eutrophic units concentrate in intensively cultivated lowlands (8.9%). Relative to the baseline, 49.5% of watersheds change trophic class, with 45.5% shifting towards higher trophic status. Our results demonstrate that plant community trophic signatures can provide a reproducible, observation-based indicator for mapping and tracking terrestrial eutrophication, complementing pressure-based nitrogen budgets and supporting monitoring, conservation prioritisation, restoration planning, and land-use decision-making. • Plant community composition provides a scalable, observation-based proxy of nutrient enrichment. • We map trophic status (oligo/meso/eutrophic) across Europe at HydroBASINS watershed level-7. • A reconstructed pre-fertiliser baseline suggests ∼49.5% of watersheds shifted towards higher trophic status. • The approach supports monitoring and prioritisation for restoration and land-use planning at watershed scale. • We provide cleaned occurrence data, derived spatial layers, and a fully documented workflow for reproducibility.