Human migration on a heating planet: A scoping review

Whilst people’s migration outcomes may be influenced by climate change, the interaction of heat with migration and migrants is little understood. This scoping review explores the relationship between heat and human migration, focusing on i) whether and how heat functions as a driver of migration, and ii) how migrants are impacted by heat across the migratory journey. Four databases were searched for peer-reviewed literature to identify studies reporting on the heat-migration nexus through 18 June 2021, alongside a grey literature search. Of 12,149 peer-reviewed and 476 grey literature records, 187 articles were screened in full, resulting in the inclusion of 50 records (47 peer-reviewed, 3 grey). Publications assessed the impact of heat on human migration (n = 32), or the experience of heat among migrants (n = 18). In the former, 16/32 report a significant positive association where exposure to heat increases the likelihood of migration or intention to migrate. Moderating factors in the heat-migration pathway include other climatic factors, agricultural productivity, economic opportunities, age, and gender. The vast majority of studies assessing the impact of heat on migrants reported negative impacts of heat (such as heat related illness, heat stress and premature mortality) among migrants compared to non-migrants. Heat impacts were aggravated by poor infrastructure, insufficient workplace adaptations, lower educational level, and socio-economic factors. Findings suggest heat may influence migratory patterns in terms of people’s intention to move, risk when on the move, and consequences of heat for settled migrants. However, the heterogeneous results suggest heat may not be a driver of migration in all contexts. No literature reported on a so-called ‘temperature threshold’ above which migration is certain. Developing comparability in measurements of heat, heat impacts, and definitions of environmentally-induced migration and migrants may support future research on, risk reduction for, and response to the impact of heat on migration and migrants.