Rising temperatures due to climate change are likely affecting human migration patterns, according to a new study by Rita Issa of University College London and colleagues, published May 24 in the open access journal PLOS Climate.

Over the past decade, heat waves have been frequent and surface temperatures have been the warmest on record. As the planet warms, many people are expected to leave their homes to escape extreme temperatures. However, the exact role of heat in human migration is not yet clear.

To shed light on this relationship, Issa’s team conducted a review of research papers, annual reports, working papers, government documents and scientific literature examining the impact of heat on human migration or the heat experienced by migrants during their journey.

Of the 32 studies that examined how heat affects migration, half found an association between heat exposure and the likelihood that a person will migrate. The vast majority of the 18 studies that assessed the effects of heat on migrants during their journey reported negative health consequences such as heat-related illness, heat stress and early mortality.

The study also reports that people were more affected by the heat if they lived in regions with poor infrastructure, or had inadequate workplace adaptations, lower levels of education and low socioeconomic status.

The new study’s findings suggest that heat likely influences human migration patterns, including the timing of when people move, the risks they face along the way and the heat they may experience once they’ve settled in.

However, the fact that only half of the included studies found an association between heat and migration suggests that heat is not the only factor driving migration. The researchers point out that no “temperature threshold” has been reported in any literature above which humans are certain to migrate.

Instead, they propose the development of accepted ways to compare temperature measurements, heat effects and environmental factors that drive migration, which they say would support future efforts to study climate migrants and implement policies that protect them from harm.

The authors add: “Migration is a valid adaptive response to extreme heat. Part of the reason there is no set temperature at which people will migrate is to put in place adaptive measures that limit the effects of extreme heat, as we see in places like the UEA where air conditioning is widely used. However, the poorest and most marginalized often remain vulnerable to extreme temperatures, including migrants. These findings provide a double opportunity for action: decisive policies to limit global warming upstream by reducing carbon and other greenhouse gas emissions; and adaptive strategies that take into account human vulnerability – ranging from urban planning, occupational adaptations, household adaptations and more – to help reduce the impact of heat on human health, well-being and productivity. ”

Magazine reference

  1. Issa R, Robin van Daalen K, Faddoul A, Collias L, James R, Chaudhry UAR, et al. (2023) Human migration on a heated planet: a scoping review. PLOS climate 2(5): e0000214. DOI: 10.1371/journal.pclm.0000214