On the Relation Between Hydrologic Variability and Violence

The purported link between climate and conflict has drawn increasing recent research attention. While increasing empirical evidence suggests a robust relation between climate (precipitation and temperature) anomalies and the emergence of violence across scales, the implicated mechanisms are poorly understood. Strong empirical correlations between climate, poverty and violence point toward income shocks as a potentially important causal pathway. This suggests that FEW systems may play an important role in the emergence of violence, particularly in rural developing regions where livelihoods are tightly linked to crop production.

Recent decision-theoretical models in economics and political sciences have tied conflictive behavior to resources variability (temporary droughts), as opposed to long term scarcity (desertification). Yet the direction and sensitivity of that effect has not been appropriately characterized (and can be counterintuitive, as we shall show). Furthermore, the respective roles of catchments, food, energy and water infrastructure, and farmer adaptation in modulating the relation between climate variability and conflict is not well understood.

We derive a game theoretical model of farmer behavior, where rational individuals attack their neighbors if the opportunity costs of foregoing current crop production (which are low in bad years) are exceeded by the expected future returns of the conquered land. Underlying probability density functions of crop production are represented realistically, using a probabilistic model of runoff generation, and tied to climate, catchment and infrastructure characteristics. Results point toward a non-monotonic relation between resources variability and conflict. We tie this counter-intuitive behavior to two distinct, and sometimes counteracting effects: (i) the direct effect of change in climate variability on crop production and (ii) the indirect effect of farmers adapting to new climate conditions by changing their behavioral thresholds for violence.