Fertile ground for conflict: evidence revisited using spatial first differences

In this paper, we revisit the empirical evidence regarding the effect of variations in soil fertility on violence at the local level. Recent evidence shows that as input (fertilizer) prices rise, poor soil productivity exacerbates income inequality and increases the tendency for conflict within and across ethnic groups, especially where soil fertility is more heterogeneous. However, spatial modeling with dense observational units in physical space is susceptible to spatial dependence and heterogeneity. Tackling such econometric issues requires a robust research design to address unobserved heterogeneity. Our main contribution is methodological: we use local soil nutrient availability measurements to proxy soil fertility and employ the spatial first differences (SFD) approach to investigate the effect of soil quality on local conflict. We show that soil nutrient heterogeneity is associated with conflicts and that this relationship is independent of climatic factors and fertilizer prices. Regarding policy, our results suggest that encouraging investment in agricultural practices that protect soil productivity might be important for reducing resource-related conflict in developing regions.