Salt affected soils in sub-Saharan Africa: an analysis of distribution from 1970 to the present

Abstract

Salt-affected soils pose a significant global challenge, impacting approximately 1 billion hectares worldwide, including 80 million hectares in Africa. This systematic review, conducted using the PRISMA framework, focuses on the extent and distribution of salt-affected soils in Sub-Saharan Africa (SSA) from 1970 to the present. The review revealed that salt affects about 65.6 million hectares of SSA's soils. The worst areas are near the coast, in river deltas like the Nile Delta, and in dry areas that get a lot of water from irrigation. Significantly affected areas include Eastern Africa, the Lake Chad Basin, and the West African coast. Ethiopia is the most affected country (11 million hectares) due to inadequate irrigation and poor drainage. The review reveals discrepancies in documentation, favoring coastal regions such as Senegal, Tanzania, and Kenya over inland areas like Chad and Mali. It also identifies the reliance on older FAO reports based on Solonchaks (saline soils) and Solonetz (sodic soils) to estimate the area coverage of salt-affected soils from the FAO/Unesco Soil Map in 1970–1981. The lack of current and updated data highlights the need for an expanded knowledge base on this topic. There is a pressing need to use data from the field and the lab, soil databases like WoSIS and HWSD, and environmental covariates gathered from remote sensing to create digital fine-scale salinity maps. The review also suggests saline agriculture, utilizing brackish water and salt-tolerant crops, as a viable strategy for rehabilitating severely affected areas, such as the Nile Delta and coastal zones.