A successful agricultural sector depends on the interplay of a wide variety of agro-ecological, economic, and societal factors. Soil health makes up a very important piece of this puzzle; soil loss and infertility pose a significant threat to overall economic development in countries that depend largely on agriculture. This includes many countries in Africa south of the Sahara.
FAO recently conducted a study of soil loss in Malawi, in partnership with the Poverty-Environment Initiative (PEI) of the United Nations Development Programme (UNDP) and the United Nations Environment Programme (UNEP). The three soil types most commonly found throughout the country are particularly susceptible to erosion due to their physical and chemical properties; in addition, the country has seen significant decline (nine percent from 1991-2010) in the amount of land planted in natural forest cover in favor of increased agricultural land. While this increase in cropland could have benefits for the country’s agricultural yields, it could also have continued negative impacts on the country’s soil if proper soil management techniques are not used on the expanded cropland.
The FAO report builds on previous soil studies conducted in Malawi since 1970; much of this previous literature focused on plot-scale studies of soil loss rates using empirical soil loss estimation models such as SLEMSA (Estimation Model for Southern Africa). The majority of these plot-level studies have found soil loss rates between 0 and 20 ton/ha/year. Only a few existing studies have taken a national scope; these have estimated that Malawi has seen national average soil loss rates of 33 ton/ha/year. The FAO study implements the SLEMSA model to estimate topsoil loss on a national scale in order to track the history of topsoil loss rates over the past 10 years, identify potential drivers of soil loss, and better plan future soil loss assessment programs.
The study finds that in 2014, the national average soil loss rate was 29/ton/ha/year. The northern regions of the country saw moderate soil loss rates, ranging between 0.4 and 39 ton/ha/year; contributing factors in this region appear to be topography (many steep slopes), fragile and shallow soil types, erosion caused by high rainfall, and poor soil management practices. In addition, time-series analysis of soil loss trends from 2000 to 2014 show that soil loss rates in the northern areas increased during this period; several areas that experienced this increased soil loss also saw changes in land use from natural forest to agricultural land during the same period, highlighting the impact that such land use changes can have on soil health without proper management.
The southern areas of the country, on the other hand, were found to have had declining soil loss rates between 2000 and 2014; in some areas in the south, soil loss rates fell to less than 10 ton/ha/year by the end of that period.
The study identifies two main factors behind Malawi’s high soil loss rates: fragile soils on steep slopes and erosive rainfall. Human activities can also exacerbate these factors, however. Engaging in agricultural activities in fragile soils or steep slopes plays a large role in increasing the rate of soil loss. The expansion of Malawi’s agricultural land at the cost of natural forest cover has reduced vegetation cover and exposed more soil to the country’s erosive rainfall. In addition, sustainable land management policies have not been adequately implemented to protect vegetation cover and ensure the sustainable use of non-renewable natural resources.
The FAO study ends with several recommendations for future land management and soil management studies, as well as land management and soil management policies.
In terms of policies, the study suggests that staff in Malawi’s Land Resources Conservation Department (LRCD) could be better supported through training in software and models to monitor soil loss and environmental resource use throughout the country. The study also suggests that the Department establish a comprehensive capacity building framework that would support this type of training. Second, the study recommends an assessment of the impact of soil loss on agricultural productivity in order to more fully identify effective policy options to deal with soil loss and poor soil management practices. Third, policymakers need to ensure that research results are used to develop strategies, programs, and extension services to implement sustainable land use and soil management practices, soil conservation programs in high-risk areas, and proper water resource and quality management practices.
The FAO study focused mainly on topsoil loss as a result of rainfall and runoff; future studies could focus on other significant soil loss types such as riverbank erosion to determine how they impact Malawi’s soil loss rates. In addition, researchers should focus on explaining the declining rates of soil loss in the country’s southern regions to draw potential lessons for use in other areas. Finally, the study recommends the creation of a monitoring network to ensure that soil loss and fertility is measured correctly on a routine basis. Such a network can go a long way in giving policymakers the scientific evidence they need to enact effective, sustainable programs.
By: Sara Gustafson, IFPRI