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

CONTEXT

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.

OBJECTIVE

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.

METHODS

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.

RESULTS AND CONCLUSIONS

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 CO₂e y⁻¹) and increased N₂O emissions (2.1 % representing 50 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.

SIGNIFICANCE

Although these results do not cancel the GHG reductions achieved by reducing livestock production (1390 Gg CO₂e 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.