For the last 50 years, much of Africa has experienced a decline in moisture availability with the strongest decline happening in areas that were already relatively dry. This trend has affected agricultural productivity and contributed to increased urban migration. This policy research working paper produced by the World Bank examines the links between agriculture and urbanisation within that time with regard to varying climate in the sub-Saharan region. More specifically, the paper makes the case that different climatic trends concerning moisture availability affects the income, employment, and migration to urban areas in different rural/urban contexts, showing how drier conditions can increase urban migration, decrease rural agricultural employment, and, depending on the urban centres reliance on local agricultural production, increase or decrease the economic productivity of urban areas.
Over 1,100 cities and towns were included in he study which uses empirical indicators, such as total night-time light emission, to gage city income and to identify correlates with climatic data. For instance, light intensity was compared to rainfall statistics for the surrounding 30km radius area from cities, in both the current and previous year. The findings indicated that while in times of decreased rainfall the subsequent increase in the urban labour force can increase urban income, this effect can be offset by decreased spending by farmers on local goods and services.
When urban sectors are primarily engaged in the production of goods and services for export outside of the district, the effect of the increased labour force prevails, and total city income rises. However, where cities exist primarily to serve agriculture with local services not traded across districts, total city income generally declines. With regards to rural occupational choice, the report finds that moisture availability correlates significantly with levels of agricultural employment. As moisture availability decreases, women are more likely to drop out of the labour force altogether, while men are more likely to move into non-farming employment.