An updated IPCC major soil types map derived from the harmonized world soil database v2.0

Abstract

Soils are the largest carbon pool in terrestrial ecosystems and play a major role in regulating the Earth’s climate. Detailed information on soil properties is necessary to evaluate current soil organic carbon (SOC) stocks, as well as past and projected carbon stock changes. Currently, the most complete dataset of global soils is the Harmonized World Soil Database (HWSD), which was updated to version 2.0 in 2023. From the HWSD, it is possible to derive a map of the Intergovernmental Panel on Climate Change (IPCC) major soil types (high activity clay (HAC), low activity clay (LAC), volcanic, sandy, spodic, wetland, and organic soils) that can be used to calculate country reference SOC stocks using the default reference SOC stock values from the IPCC guidelines for national greenhouse gas (GHG) inventories. Following the update of the HWSD, an updated 1-kilometer resolution global map of the distribution of the seven IPCC major soil types, derived from the HWSD v2.0, is presented. When comparing the IPCC major soil types maps derived from HWSD v2.0 and HWSD v1.2, it appears that 18 % of the land areas are differently classified. Changes are mostly located in northern latitudes and small islands states. They are attributable to a change in the classification of soils, from FAO90 and FAO74 classes in the HWSD v1.2 to WRB classes in the HWSD v2.0, and an extended coverage of coastal areas and small islands.These same changes lead to an average difference in country reference SOC stocks of around 3 % when comparing Tier 1 country reference SOC stocks derived from the HWSD v1.2 and v2.0.