Turning up the heat: How a warming climate might worsen violent crime in South Africa
South Africa could experience a thousand more homicides a year, were the temperature to rise by 1°C, according to a recent editorial review of the impact of temperature on violent crime. How the weather affects risk for crime is mediated by a host of other factors, the authors note. As temperatures rise, understanding heat-violence mechanisms will become increasingly important in anticipating and mitigating crime hotspots. By Andrea Teagle
Violent crime fluctuates with the weather. Between 2001 and 2012, almost half a million (418 327) homicides and 1.5 million sexual offences occurred in South Africa. Using ward-level crime data across the country, researchers from Ruhr Economic Papers – a collaboration between four German universities, including Ruhr-Universität Bochum – found that higher temperatures and droughts significantly affected levels of violent crime, as well as burglary.
Specifically, a 2.7°C increase in the maximum temperature (or one standard deviation away from the average) in an average month increased total crime counts by 3.7%. The same increase in minimum monthly temperature — which the Ruhr team read as a proxy for night-time weather conditions — led to an increase in crime of 5.3%, suggesting that night temperatures have a greater effect on crime rates.
The findings support other research that suggests that higher temperatures increase the risk of violence. Hotter weather increases irritability and hostility; it also has an impact on socioeconomic conditions such as drought and water scarcity that influence human behaviour.
Studies suggest that rising temperatures might have a greater impact on crime when people are already under strain — for example, in areas experiencing widespread poverty, high crime rates, gender imbalances or political unrest.
Additionally, the effect of temperatures on violence is not necessarily linear, as Prof Matthew Chersich of the Wits Reproductive Health and HIV Institute and his colleagues noted in a recent South African Medical Journal guest editorial. Warmer temperatures might initially lead to greater violence, but extreme heat tends to diminish activity, so crime might be expected to plateau or even drop.
The effect size differswidely, and untangling the impact of weather from other drivers of crime is notoriously challenging. However, given South Africa’s already violent climate, and the fact that it is going to get warmer, it is worth asking – what impact will a rising temperature have on crime rates?
Impact on vulnerable populations
In their guest editorial, Chersich and his team, including Dr Ian Edelstein, a former HSRC researcher, estimated a 4– 5% increase in local homicides were the temperature to increase by 1°C. This translates into 800 – 1000 homicides on top of the current homicide count of 20 336 per year.
The estimate is based on the Ruhr findings, as well as those of 15 other studies investigating the heat-violence nexus. Of those, 6 found a positive correlation that was statistically significant. Chersich and his colleagues note that their estimate is conservative - one of the reviewed studies estimated a 17% increase in homicides across Africa for a 1°C temperature increase. Another, a 2018 study based in Tshwane, found a 50% higher rate of violent crime on hotter days, on average, over a period of 5 years.
However, the authors recommend additional modelling using empirical data and including mediating factors to refine the expected impact.
While Chersich and his colleagues’ 4–5% estimate pertained to homicides, results from the Ruhr study suggest that higher temperatures are likely to result in an even greater increase in gender-based violence. Based on the 2001–2012 data, they found that an increase of one standard deviation in daily minimum temperature in an average month caused sexual crimes to surge by over 8.6%.
Individuals already at higher risk for violence are likely to bear the brunt of the increase. Although the Ruhr study did not measure xenophobic attacks, the same mechanism likely applies to foreign nationals.
“Importantly, physical environmental triggers of violence, such as heat, are set against the backdrop of complex social processes, poor governance and historical circumstances that influence violence in South Africa,” Chersich and colleagues write.
Mechanisms for weather-induced violence
In addition to affecting mood, weather can also influence social environments in ways that may change the costs and benefits of committing a crime on a particular day: a crowded outdoor area might make pick-pocketing easier, for example.
Warm weather also has a lagged influence on non-violent crime, according to the Ruhr study. The data showed that spikes in property crime in rural areas followed poor harvests, as households reliant on agriculture turned to other means to make up the shortfalls.
And, while the editorial was concerned with individual cases of crime, a large body of researchshows that weather is associated with collective violence and conflict. As in the case of individual crimes, extreme weather interacts with, and exacerbates, existing drivers, such as political unrest, dissatisfaction with government services, and gang warfare.
Rising temperatures
According to the Intergovernmental Panel on Climate Change’s special report on climate change, unless ambitious measures are taken, by the end of the century, the world will easily surpass a 1.5°C temperature increase above pre-industrial levels – which is around 0.5°C away from where we are now. And in inland South Africa, temperatures are projected to increase at twice the global average.
Climate change also increases the risk of conflict through resource scarcity and population displacement, or ‘eco-migration’, is anticipated to be a primary driver of conflict in the coming decades. By 2050, an estimated 150 to 200 million people will be displaced due to extreme weather conditions, drought and rising sea levels, according to Unesco.
In South Africa, evidence suggests that internal displacement, particularly of low-income groups, is already happening.
Chersich and his colleagues note that a better understanding of the heat-violence pathways might help authorities to deal better with increased crime risk ahead of hot spells in different parts of the country. Preventative measures could include air conditioning in schools or prisons, and greater police presence in high-crime areas, for example, while police and health professionals could prepare for more cases of assault ahead of heat spikes.
Author: Andrea Teagle
ateagle@hsrc.ac.za