A Global Comparison of Fertility Responses to Heat

Vinod Kannankeril , University of Bologna

Rising global temperatures may alter human reproductive patterns, yet the extent to which men’s fertility responds differently to heat remains unclear. This study examines sex-differentiated fertility responses to temperature using global male and female age-specific fertility rates (ASFR) linked with country-year temperature anomalies and cooling degree days. Fixed-effects panel regressions were estimated to isolate within-country variation. Results indicate modest, cumulative fertility reductions under hotter conditions, with weak immediate effects. Male fertility responses show slight postponement, a higher mean age at fatherhood and increased births at ages = 40—while overall male and female total fertility rate slopes are statistically similar. These findings suggest that heat influences fertility timing more than its quantum and that biological sensitivity among men may contribute to subtle demographic shifts. Incorporating male fertility sensitivity into climate–population models can improve projections and inform reproductive health adaptation in heat-exposed regions.

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 Presented in Session P80. Flash Session Environment, Human Capital and Inequalities