Modeling Organic Agriculture Expansion in the EU: Assessing Productivity and Environmental Trade-Offs.

Intensive agriculture has led to significant soil degradation and nutrient surpluses in the EU, prompting the need for more sustainable practices. Organic agriculture is often considered a strategy to produce food more sustainably, albeit with challenges such as yield reduction. Here, we estimate the impacts of expanding organic agriculture to 25% of agricultural land in the EU and UK-a key target of the European Commission's Farm to Fork Strategy-using a spatially explicit biogeochemical model, focusing on changes in crop yields in combination with C, N, and P fluxes and stocks. Achieving the 25% target could improve 0.8%-1.4% of degraded soil areas (out of ~49.0 million ha that exceed at least one degradation criterion based on N surplus, excess soil P, or soil erosion thresholds), quantifiably reduce dependency on mineral fertilizers (P by 15.8%-16.0% and N by 15.2%-15.7%), and either lessen or maintain current eutrophication impacts on freshwater fish. However, these benefits come with a trade-off of about 6.5% reduction in average yields of grain and tuber, partly due to increased fodder production replacing grain and tuber crops in the rotation. Applying the 25% target area EU-wide or per member state minimally affects the overall results. An additional cover crop scenario demonstrated the benefits of increased N fixation, improved yields, and mitigating SOC decline, but also resulted in higher impacts on freshwater biodiversity due to increased N losses. Thus, it highlights the importance of considering interconnected N, P, and C cycles alongside crop yields and potential feedbacks. This approach offers valuable insights into the synergies and trade-offs between agricultural practices and environmental consequences at high spatial resolution.