Hotter than normal temperatures raise the risk of violent conflict in East Africa, while increased rainfall makes such disturbances less likely, according to a new study conducted by the US National Academy of Sciences.

For both climate variables, there is about a 30 per cent change in the likelihood of violence occurring in an affected area, the study finds.

The results appear to reinforce warnings of climate change leading to more conflict in Africa, which is regarded as particularly vulnerable to the effects of sharp shifts in temperature and precipitation.

President Barack Obama, for example, has said climate change poses an “urgent, serious and growing threat” because crop failures and loss of livestock “breed hunger and conflict.”

But the scientists responsible for the study published last week point out that higher temperatures and rainfall have much influence on the chances of conflict than do factors such as population density, ethnic rivalry and denial of political rights.

In fact, the study notes, “population is the most important predictor of the number of violent events in an area.”

The National Academy of Sciences study is based on 16,359 individual violent events in a total of nine east African countries between 1990 and 2009. Kenya and Uganda each accounted for nearly 2,500 of these outbreaks during that period, while Tanzania was far more peaceful, with only 281 flare-ups reported.
In pastoralist communities, the study finds, traditionally competitive groups are spread further apart from one another during rainier times, thus diminishing the chances of conflict.

Conversely, the risk of violence between pastoral groups rises when temperatures become much warmer than normal, the US scientists say.

Increases of 2.5 degrees Celsius cause a net income loss of about 32 per cent for pastoralists, with losses rising to about 70 per cent when temperatures soar to five degrees Celsius above normal. The drops in income reflect losses of livestock, which in turn increase “incentives to replenish the herd by raiding,” the study observes.

A seeming anomaly in the findings is that periods of low precipitation were shown to have no effect on the likelihood of conflict. Drought alone, in other words, does not raise the probability of violence in East Africa, according to the study.

For farmers, hot weather may have harmful effects on crops such as maize, the study notes. That outcome reduces income and presumably raises the risk of violence.

On the other hand, “greater than average precipitation increases agricultural productivity, which improves the availability of food and also raises incomes for households reliant on earnings from farming,” the study says.