A Critical Review of the IPCC’s Tier 1–3 Quantification Approaches for Soil Organic Carbon Estimation: Relevance and Applicability on South African Soils

Soil organic carbon (SOC) plays a crucial role in agricultural sustainability, climate change mitigation, and the assessment of carbon footprints. Several quantification approaches have been developed and used world wide to simulate the decomposition and stabilisation of SOC under varying environmental and land use conditions. Despite these developments and global use of these approaches, the intricacy, diversity, and heterogeneity in South African soils and ecological zones, present difficulties in reliably estimating and/or predicting SOC changes within the country. This paper critically examines the applicability and limitations of the Intergovernmental Panel on Climate Change (IPCC) quantification approaches, namely the Tier 1, Tier 2, and Tier 3 methods, in the context of South African soils. The review highlights the complexities and variability of South African soils and landscapes, the challenges of translating global models to the South African context, and the difficulty of achieving accurate predictions across the nation's diverse biomes and climates. The recommendations provided are aimed at improving model adaptability, emphasising the need for region-specific data and calibration to support SOC estimations and climate change mitigation efforts in South Africa and other similar countries.