Mapping of soil organic carbon stock in the Arab countries to mitigate land degradation

Abstract

Soil organic matter is a key soil component that plays a critical role in ecosystem functioning including soil productivity and resilience to erosion and drought. Most Arab countries are located in semi-arid and arid areas with dominance of drylands soils with poor organic matter content and soil quality. In line with the efforts of the FAO Global Soil Partnership (GSP) and French initiative for carbon sequestration (4 par mille); the soil organic carbon (OC) stock in the Arab countries was assessed and mapped using the FAO-UNESCO Digital Soil Map of the World (DSMW). The outputs must serve awareness raising both at the level of land users and decision makers. Results were compared with the only available national OC map, recently produced in Lebanon. Other national OC maps are under processing by the GSP and Intergovernmental Technical Panel on Soils (ITPS) within the Global Soil OC Map. Produced maps showed low OC stock in the topsoil of more than 69% of the cultivated soils with dominance of xerosols, arenosols, and lithosols. The average soil OC stock in the Arab countries is 37 ± 36 ton/ha in the topsoil and 78 ± 69 ton/ha in the standard soil depth. The total OC stock in the arable lands of the Arab countries was estimated at 50.5 gigatons (GT) with Sudan, Saudi Arabia and Algeria placed on top. The average total OC stock per one Arab country is 0.8 ± 1.7 million tons. Large standard deviation points to different pedoclimatic conditions but also to variable management and land use history. Water erosion and chaotic urban expansion caused the irreversible loss of 25 and 53.6 GT tons of OC, respectively. With increased pressure on limited soil resources, policies must address soil conservation and C sequestration to support soil productivity and improve food production.