Do heat-related health and income losses increase food insecurity? A natural experiment across 148 countries, 2014-2017

Background Climate change is expected to cause a substantial rise in food insecurity with serious consequences for human health globally1–3. Existing evidence links hot periods to food insecurity through a decline in agricultural yields in the medium- to long-term, but heat-related health impacts may influence food insecurity immediately by limiting workers’ ability to earn income1,4–6. This paper explores whether extreme heat causes immediate food insecurity through heat-related health and income reductions, and how this relationship differs across 148 countries. Methods The research design exploits a natural experiment based on the day in which people report food insecurity to survey questionnaires, matching this to weather conditions experienced by the individuals in that week. The analysis combines representative socio-demographic data at the individual level (n=497,816) from 148 countries in 2014-2017 with thermal stress data in a multi-level linear probability model. The model estimates the association between moderate-severe food insecurity and the number of hot days in the seven days leading up to the survey, accounting for age, gender, partner status, children in the household, as well as precipitation and fixed effects for the year. Findings After a hot week, on average, an additional 0.42% [95%-CI: 0.1117 to 0.7317, p=0.0077] or 34 million people worldwide are likely to experience moderate-severe food insecurity mediated by reductions in income and health. The effects are stronger in countries with lower incomes, higher agricultural employment, and more informal labour markets. Interpretation Heat increases food insecurity in the short-term by reducing people’s capability to buy food with particularly strong effects among those living in countries with more heat-exposed and informal labour markets. To prepare for a world with more frequent and intense periods of extreme heat, policymakers and researchers should carefully consider the immediate knock-on effects of climate shocks and integrate these into heat action and food security plans.