Limitations of the IPCC Methodology for Soil Carbon Assessment: Application in areas with land use change

Abstract

Considering the problem of burned areas in Portugal and the growing concern about the decarbonization of Europe, land use change (LUC) in some areas of the country becomes a strategy to achieve the goal of zero emissions. LUC can result in an increase or decrease in the stock of Soil Organic Carbon (SOC). Quantifying this element is crucial to anticipate possible future scenarios in these areas. The methodology recommended by the Intergovernmental Panel on Climate Change (IPCC) can generate misinterpretations. Therefore, this study sought to demystify its application to a Mediterranean study area with LUC using the help of QGIS software. Each land use class used SOC reference data corresponding to Level 1 of the methodology (national data) extracted from Portugal's National Greenhouse Gas Emission Inventory of 2021 (NIR-PT). The results indicated an increase in the SOC stock for the area, with an average rise of 1 t/ha-year, when the LUC moves from scrubland to hardwood forest. Although the level 1 methodology roughly estimates SOC values, it is useful when there is no local or regional data.