How Do Diet Shifts Affect the Greenhouse Gas Balance of Agricultural Soils? Denmark as a Case Study

Abstract

Current food systems account for approximately 30% of anthropogenic greenhouse gas (GHG) emissions; therefore, consumers' dietary preferences can have strong environmental consequences. This is well known for the GHG mitigation achieved by reducing animal protein consumption and associated methane emissions. However, the effects of diet shifts on the soil GHG balance have not been comprehensively evaluated yet. In our study, we employed a two-sided approach to investigate the impact of dietary changes following the EAT-Lancet diet guidelines on GHG emissions from agricultural soils. Firstly, we used the economic general equilibrium model MAGNET outputs to quantify the demand-driven changes in food consumption at the national level for the European Union (EU) under diet shift scenarios. We then used the DayCent process-based model to assess the implications for the GHG balance of agricultural soils at a regional scale, with Denmark as a case study. Our findings indicate that, compared to business-as-usual diets, the full adoption of the EAT-Lancet reference diet would cause significant carbon losses (up to 15 Mg of CO2e ha-1) and increased N2O emissions (5.8% representing 141.9 Gg CO2e y-1) from 2030 to 2100 in agricultural soils. These changes primarily stem from the reduction in animal manure application to soil and a decrease in the share of permanent grasslands. The soil GHG balance differed largely across pedo-climatic conditions. Although these results do not cancel the GHG reductions achieved by reducing enteric CH4 emissions, they underscore the challenges faced by policies aiming to create healthier food environments, which must be aligned with efforts to reduce anthropogenic GHG emissions.

Keywords: Healthy diets, soil organic carbon, nitrous oxide emissions, nitrogen budget, yield, process-based model