Session

Identifying the drivers of plant diversity is crucial for conservation and ecosystem management, especially under anthropogenic pressures and climate change. Grasslands, vital for European ecosystem services, are threatened by agricultural intensification and land use changes. We examined the effects of grazing practices and nitrogen (N) deposition on grassland plant diversity across Europe. We explored these links while considering variation in land use cover and biogeographical regions. We used a dataset of ~130,000 plant relevés from the European Vegetation Archive (EUNIS habitat type Grasslands). N deposition was obtained by spatial disaggregation of Common Agricultural Policy Regional Impact Analysis (CAPRI) model outputs. The information on grazing pressure was obtained from datasets that, for the first time, separate indoor and outdoor livestock density at the European scale. Integrated Nested Laplace Approximations (INLA) within the Stochastic Partial Differential Equation framework were used to model spatial dependencies and complex interactions. This modelling method allows fine-scale spatial variability to be captured, providing unbiased estimates on the effects of grazing and N deposition on plant species richness and functional diversity. Preliminary results for plant species richness show negative impacts of cattle grazing intensity and N atmospheric deposition, but a positive impact of caprine grazing intensity. However, results also showed strong variations across biogeographical regions and land use categories, which need to be further analysed to confirm the generalisability of the impacts of management practises on grassland plant diversity. Climatic factors such as temperature and precipitation further influence these relationships, highlighting the complex nature of biodiversity responses to environmental drivers. Our study employs spatial modelling on a large-scale plant diversity dataset, combined with unprecedented grazing intensity and N deposition data at the European level. The findings underscore the importance of considering multiple interacting factors in biodiversity assessments and offer insights for land management and policy-making to preserve grassland diversity under changing environmental conditions across Europe.