Population density, soil nutrient depletion, and economic growth in sub-Saharan Africa

Soil nutrient depletion is considered as the biophysical root cause of declining per capita food production in sub-Saharan Africa (SSA). Data from 37 countries in SSA confirm a significant relationship between population pressure, reduced fallow periods and soil nutrient depletion (including erosion), indicating a generally unsustainable dynamism between population, agriculture and environment. It is estimated that nutrient depletion accounts for about 7% of the agricultural share in the average Gross Domestic Product of SSA with national values ranging up to 25%, indicating soil nutrient mining as a significant basis of current economic performance. With respect to increasing population densities, it is argued that more than proper soil management will be required to sustain food security. While soil scientists and farmers can reduce the speed of the dynamism only, policy-makers are requested to address also the demographic and economic root causes of soil degradation. Care should be taken that the ‘obvious’ simplicity of the dynamism will not provide the groundwork for corresponding blueprint solutions, ignoring the diversity of the biophysical and socio-economic environment of SSA.