Heat-related mortality mapping to inform heat adaptation measures

Climate change has increased summer air temperatures, leading to a significant rise in heat-related mortality. Since heat-related mortality varies spatially based on the distribution of landscape variables, population exposure, and vulnerability factors, it is crucial to identify areas with high heat-related mortality for prioritizing heat-adaptation measures. However, previous studies have been limited to quantify municipal or city level heat-related mortality and have not inform how landscape variables could reduce heat-related mortality spatially. We used a combined method of regional urban climate model and a relative risk function to quantify heat-related mortality in the Tokyo Metropolitan Area at a 1 km resolution. We found that densely populated areas around the central business district had high heat-related mortality (> 1.12 deaths/km2/2mon), and that heat-related mortality rate was negatively correlated with the fraction of water bodies, green areas, and road areas. Maximum greening (a 47% increase in green area fraction) could reduce total mortality by 9%, with a greater impact in high-risk areas. Our findings can support Tokyo Metropolitan’s 2030 greening goal is not enough to mitigate heat-mortality (implementing 1.1 km2 of green area may reduce 0.3 mortalities during July and August) even if it is implemented in the priority areas. It underscores the importance of quantifying the effects of landscape variable-based solutions and prioritizing high-risk areas for future adaptation efforts.