City isolation and not size may drive violence in Africa

There is an assumption that larger cities are inherently more violent than smaller ones, but this is not always the case. A new study of African cities has found the level of isolation could play a more crucial role in determining violence.

The research is led by Complexity Science Hub (CSH) in Vienna with support from the University of Exeter and published in Nature Communications. The study found the 10 per cent of biggest cities in Africa (216 cities in total) contain 66 per cent of the continent’s urban population, but only 33 per cent of the fatalities linked to politically motivated violence over the past 22 years.

Lead researcher Rafael Prieto-Curiel from CSH said: “Our findings clearly indicates that size alone cannot explain levels of urban violence and the importance of moving beyond the idea of universal laws when studying cities. We need to be very conscious of how heterogeneous the world is and can’t think of cities as a universal phenomenon that can be explained with fixed physical laws. Big cities are not inherently violent.”

The study used OpenStreetMap data to construct a network of all highways in Africa. Results showed cities with only one or two highway connections experienced nearly seven times more violence against civilians per 100,000 residents than cities with seven or more highways.

Comparing the ten per cent most isolated cities with the ten per cent least isolated, the researchers found the former faced more than seven times the level of violence against civilians. Moreover, looking at the top 25 per cent of most and least isolated cities from 2000 to 2020 revealed that the gap has widened over time and isolated cities have become more violent in recent years.

To refine the analysis, Professor Ronaldo Menezes from the University of Exeter helped introduce a second measure of isolation – city centrality. This captures not only how many highways lead to a city, but also how connected it is within the broader network of cities.

Professor Menezes said: “We needed a new way of understanding why smaller, more remote African cities experience disproportionately higher levels of political violence. My background in network science and crime analysis, along with my experience working with police forces in Brazil and the UK, helped map the relationship between urban isolation and violence intensity in African cities. Our research has given vital insights into potential interventions such as targeted security and infrastructure planning.”

The researchers built a model that detected the shortest route for residents of every city in Africa to every other city on the continent and simulated millions of those journeys, then measured how many of them pass through a given city. The findings showed a similar picture – for example, in cities ranking in the lowest 25 per cent for city centrality, lethality rates were 15 times higher than in the 25 per cent with highest city centrality.

To study violence, the researchers relied on data from ACLED (Armed Conflict Location & Event Data Project), which compiles media reports of armed conflicts worldwide. For this study, they analysed nearly 300,000 politically motivated events in Africa between 2000 and 2023, linked to almost 600,000 casualties. Researchers noted this is not a comprehensive geography of conflict in Africa and also that violence in small, remote cities is likely underreported, meaning the disparities may be even greater than observed.

The paper titled ‘Violence, City Size and Geographical Isolation in African Cities’ is published in Nature Communications.