As summer heat waves grow more frequent and extreme because of climate change, so do the risks to human health. But while the immediate effects of heat are well understood, there is an insidious secondary effect, according to a new study: People go hungry.
"Households across the world struggle to afford to buy food when it gets too hot to work and earn an income,” says Carolin Kroeger, a doctoral researcher at the University of Oxford who authored the study, which was published on Tuesday in the journal Nature Human Behaviour.
Kroeger’s work found that a week of hot temperatures — defined as a week with at least three days whose temperatures rank in the hottest 10% of the year — was associated with a small but significant increase in household food insecurity. Extrapolated across a population the size of India’s, for example, that would mean over 8 million more people struggling to feed themselves properly during seven days of extreme heat.
When temperatures climb, people whose income is dependent on their productivity may earn less, either because they forgo work or because the heat makes them less productive. In 2021, 470 billion work hours were lost worldwide to extreme heat, the equivalent of roughly 1.5 weeks of labour per person.
"If you are a brick worker paid by the number of bricks you carry, then obviously you're going to get paid less on a hot day,” Kroeger says.
Antonella Mazzone, a University of Bristol researcher who studies the impact of heat but was not involved in the study, says Kroeger’s paper "presents an innovative approach and methodological exploration of the intersection between short-term food insecurity and heat-related challenges.”
While the study was correlative, and stops short of being able to prove that increased heat causes food insecurity, the "correlation between informal, precarious outdoor employment and food insecurity is logically coherent,” says Mazzone who called the paper "a wake-up call on the issue of climate change and food security that should make us think (about) what can be done to mitigate these circumstances and how to intervene promptly.”
Kroeger’s study drew its conclusions by leveraging over a half a million observations from the Gallup World Poll, which each year surveys adults in almost every country on metrics that include food insecurity. Kroeger used that data, along with temperature data from the Universal Thermal Climate Index, to compare those who experienced a hot week against those who didn’t. She found that people who experienced a hot week were more likely to face food insecurity that week, and that a higher number of hot days was associated with increasing rates of food insecurity.
"Countries with more vulnerable forms of employment are more affected,” Kroeger says. Day laborers, agricultural workers, and people in informal employment are less likely to have a safety net. In the U.S., for example, many agricultural workers are also undocumented, which means they have less access to social services. Among indoor workers, Kroeger points to textile factories, which "are really poorly insulated and ventilated and have no air conditioning.”
Mazzone notes that many places also lack access to refrigeration. "The presence of a refrigerator significantly reduces the experience of food insecurity compared to those without such facilities,” she says. Strengthening social networks — friends and family, as well as formal charitable organizations and NGOs — can also help.
Improving worker safety and the attendant risk of food insecurity will be increasingly important as the world heats up. For one example of a near-term solution, Kroeger points to a Rockefeller Foundation microinsurance pilot available to informal workers in India. Women make payments into insurance accounts, "and then on hot days they're paid out so that they don't have to go to work if it's really hot and might be threatening their health,” Kroeger says.
Meanwhile, some governments are actively rolling back worker protections. Earlier this year, Texas Governor George Abbott signed a bill that effectively overturned local ordinances mandating rest breaks for outdoor workers.
Long term, Kroeger says, cities, workplaces and buildings will need to be designed in ways that facilitate passive cooling to help workers avoid having to choose between risking their health and going hungry.
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