Academics do not agree on the relationship between climate change and armed conflicts. Weather events driven by climate change, like droughts and extreme precipitation, might be societally destabilizing. But attempts to determine whether this connection is happening in the real world have produced ambiguous and sometimes contradictory results.

A new study published in PNAS looks at up-to-date conflict data from 1989-2014 in Asia and Africa, examining the relationship between these events and droughts. The study finds that droughts affect the level of conflict, but only in poor societies that are dependent on agriculture.

Drought can incite conflict because it can cause food scarcity, but is that actually happening today? To probe this relationship, the authors used geo-referenced data on armed conflict events between ethnic groups. The procedure used to link the ethnic groups to conflict behavior included consideration of how localized drought affected groups’ behavior regardless of the physical location of the fighting relative to the drought. In other words, if the group suffered a drought but ended up fighting in a region that received sufficient rain, that still counted. For this analysis, "ethnic group" was defined as discrete groups of humans with a shared culture and language living in the same geographic space.

On top of this geographic data, the authors overlayed ethnicity and land use data in addition to drought statistics. They then calculated the extent of drought in agricultural areas during the growing season of each of the dominant local crops. They used something called Standardized Precipitation Evapotranspiration Indexes (SPEI) as the primary indicator of drought, because this measure captures both precipitation anomalies and variations in things that determine evaporation rates.

Overall, their analysis revealed a mixed pattern. Point estimates for the drought’s effect on conflict were positive, suggesting that drought was likely to be associated with an increase in civil conflict. However, the rates of increase for these relationships weren’t at a 95 percent confidence level (the standard used in most science), which makes it hard to make inferences based on this data. This could be because there was a high level of variability in the relationships—a variability that depended on which other factors were included in the model, such as size of group, national GDP, and spillover effects from neighboring groups’ conflicts.

The authors found that drought had a stronger effect on conflict when an ethnic group’s agricultural dependence was included in the model. If groups were primarily agrarian, they were at much higher risk of civil conflict during times of food scarcity for instance. Additionally, if the level of economic development was included in the model, then the data showed that the groups most vulnerable to drought-induced conflicts live in less developed regions, where access to other food sources may be limited.

Overall, the analysis showed that most groups are quite resilient to the deleterious effects of drought. However, those that were more politically marginalized and agriculturally dependent, particularly those in less developed regions, were at a higher risk of civil conflict during times of environmental hardship.

The authors conclude their paper by saying that the impact of drought on conflict in most circumstances is limited. The exceptions are groups that are particularly vulnerable where drought does increase the likelihood of conflict. This finding is consistent with a troubling truth about climate-related vulnerabilities: people whose baseline vulnerability is higher are more likely to be adversely affected by climate-related pressures. Those who are already in good shape are less likely to be affected.

This reality is unsettling because the societies with the most power to reduce their contributions to climate change are typically wealthier and more secure, while the people who will most benefit from these changes can’t do much about the problem.

PNAS, 2016. DOI: 10.1073/pnas.1607542113 (About DOIs).