Soil carbon sequestration potential bounded by population growth, land availability, food production, and climate change

Improving soil management to enhance soil carbon sequestration (SCS)-a cost-efficient carbon dioxide (CO2) removal approach-can result in co-benefits or trade-offs. Here we address this issue by setting up a modeling framework for Switzerland that combines soil carbon (C) storage, food production and agricultural greenhouse gas (GHG) emissions. The link to food production is crucial because crop types and livestock numbers influence soil organic C (SOC) stocks, through soil C inputs from plants and manure. We estimated SCS rates for the years 2020-2050 for three scenarios, each with two variants for biochar: cover cropping (0.30 t CO2 equivalents [CO2-eq] ha(-1) yr(-1)), biochar addition (0.36-1.8 t CO2-eq ha(-1) yr(-1)) and agroforestry-biochar addition (2.2-2.3 t CO2-eq ha(-1) yr(-1)). Different limiting factors (land and biomass availability, population growth) affected SCS rates and indicated that they cannot be sustained until 2100 under all scenarios (cover cropping: 0.10 t CO2-eq ha(-1) yr(-1) [2051-2100]; biochar addition: 0.35-1.8 t CO2-eq ha(-1) yr(-1); agroforestry-biochar addition: 1.0-1.7 t CO2-eq ha(-1) yr(-1)). This information together with the associated GHG emissions is critical for planning net zero strategies and highlights the importance of integrated assessments that capture links between SCS and the food system.