impact on cities as global climate change progresses. At present, around one-fifth of working hours per year are currently too hot for high-intensity physical work to be conducted safely based on occupational health and safety standards. The number of lost working hours due to extreme heat is expected to rise by up to 30% in the case of Chennai, putting more than 4% of the city’s economic output at risk. While labor productivity outputs are crucial, it is however important to analyze these alongside expected health impacts, given that heatwaves result in illness and premature death concentrated among vulnerable segments of the population including the elderly. Consistent with existing epidemiological studies of extreme heat in India, our modeling estimates that the crude death rate may rise by 50% by 2050 under high emission scenario assuming a ‘no intervention’ scenario (Zhao et al. 2021).

Cities in India, and globally, are increasingly adopting measures to mitigate the diverse adverse impacts of extreme heat upon their citizens, economies, and infrastructure. The Ahmedabad Heat Action Plan has emerged as one ‘best practice’ model that other cities in India and internationally have emulated considering its multi-sectoral actions ranging from measures with a long time horizon that cool the physical spaces of the city (e.g., tree planting and cool roofs) and measures with a short time horizon that seek to save lives during heatwaves (e.g., issuance of color-coded alerts, activation of extreme heat protocols in hospitals, and measures to protect heat-affected workers). In this paper, we set out to model the benefits from adopting multi-sectoral packages of heat mitigation actions in Indian cities and to compare the benefit-cost ratios of the different actions.

We found benefit-cost ratios for the urban greening and heat-health early warning system interventions to be significantly positive. Increasing the area under tree canopy cover by 10% to 30% can be expected to yield air temperature reductions of up to 1.5°C on a localized basis, according to our analysis, which is in line with findings of a meta-analysis from European city-level studies of tree canopy cooling benefits (Iungman et al. 2023). Quantifying benefits of such temperature reduction based on averted mortality and labor productivity loss yields a positive benefit-cost ratio for urban tree planting. It is important to note that increasing tree cover and other natural assets in urban areas offers multiple advantages beyond reducing daily temperatures and heat stress. These enhancements create cooling areas for laborers, street vendors, workers, and commuters during hot days. Secondly, they play a significant role in flood risk management and provide a range of physical and mental health benefits to residents. This would be a significant advantage in labor surplus economies such as India, which are grappling with the challenge of addressing youth unemployment. These broader benefits may be equally or even more substantial in scale compared to the effects discussed here. Our finding that tree planting yields a benefit-cost ratio of 3:1 or higher suggests that such interventions ‘pay for themselves’ through mitigating adverse impacts of extreme heat on health and labor productivity alone, with their real benefit-cost ratios likely to be significantly higher, particularly in cases where tree planting brings significant flood mitigation benefits.

Our analysis also suggests that, among the heat mitigation interventions that cities can adopt, heat-health early warning systems has a particularly high ratio of benefits to costs. Indeed, with a benefit-cost ratio of 50:1 or higher, for heat warning systems – as well as high levels of 18