How do diet shifts affect the greenhouse gas balance of agricultural soils? Denmark as a case study

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 impact of diet shifts on the soil GHG balance has not been comprehensively evaluated yet. To comprehensively assess the impact of the EAT-Lancet healthy diet on the net soil GHG balance at a national level with an advanced process-based modelling framework, using Denmark as a case study. We adopted a two-sided approach. Firstly, we used the economic general equilibrium model MAGNET to quantify the demand-driven changes in food consumption and land use at the national level following the adoption of the EAT-Lancet healthy diet for the European Union (EU). We then used the DayCent process-based biogeochemical model to assess the implications of these changes for the GHG balance of agricultural soils at a national scale in Denmark. 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 480 Gg CO 2 e y −1 ) and increased N 2 O emissions (2.1 % representing 50 Gg CO 2 e 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 livestock production (1390 Gg CO 2 e y −1 ), they underscore the importance of comprehensively accounting for soil GHG emissions as they offset some of the benefits of adopting a plant-based healthy diet. Finally, the marked regional variation in net soil GHG balances highlights the need for spatially explicit assessments in other regions and at larger scales. • Novel methodology to assess the impact of a healthy diet on soil greenhouse gases. • Higher soil organic carbon losses and nitrous oxide emissions under a healthy diet. • Changes due to reduced organic carbon input and elevated mineral nitrogen in the soil. • The impact of a diet shift varies considerably across regions. • Larger-scale spatially explicit assessments are needed.