This is a critical moment for land use policy globally, with many countries (e.g. the UK and the European Union) currently undertaking significant green reforms of their agricultural policies. Despite their importance for maintaining agricultural outputs and plant diversity, the effects of artificial soil enrichment on pollinators remain poorly understood. Our two-year study at the world’s longest-running ecological experiment, Park Grass, Rothamsted, […] indicate[s] a large and significant trade-off between productivity and biodiversity. Our findings are a salutary reminder of the challenge in reconciling conflicting aims in farmland management and strongly suggest that financial incentives are necessary to offset yield reductions to improve biodiversity outcomes in agricultural grasslands.

Our most important and challenging finding is the existence of a trade-off between flower and pollinator diversity and grassland yield (Fig. 3 and Figure S4, Supplementary Materials). This shows that to maximise flower species richness, and hence also pollinator species richness, a significant drop in fertility is required and will reduce yield. […]