News - January 28, 2016

Extreme weather leads to violence

Joris Tielens

Extremely heavy rainfall and drought influenced levels of violence in colonial Nigeria. PhD candidate Kostadis Papaioannou has demonstrated this using a method which could help now in refuting false correlations.

Google ‘spurious correlations’ and you will find, for example, a statistical correlation between people who drown in a swimming pool and the number of films starring Nicolas Cage. This is nonsense of course, because there is no causal relationship. Yet there can be a danger of this even in more serious research, says Papaioannou, a PhD candidate in the Agricultural and Environmental History chair group.

In recent years there have been an increasing number of studies of the relation between climate change and violence. The theory is that extreme weather harms agriculture, affecting the food supply and causing more conflict. One example is the high food prices which led to the Arab Spring in Egypt. But, says Papaioannou: ‘the majority of these studies only look for statistical correlations without verifying whether there is a causal relationship.’

The economic historian did verify this. He first compared rainfall figures with the number of prisoners, court cases and murders in colonial Nigeria from 1912 to 1945. There was no question of climate change yet then, but there were weather extremes. The figures show that periods of extreme drought or heavy rains corresponded to periods of serious violence.

In order to establish whether there was also a causal relationship, Papaioannou studied reports by British colonial officers. And they spoke regularly of drought and floods as the cause of conflict. He also noted that the relationship was weaker in areas with more cash crops providing additional income.  Papaioannou sees this as reason to promote export agriculture in Africa now. His results will be published in the Journal of Political Geography this month.