Upgrading Slums as Pathway to Climate Resiliency

This study provides empirical evidence that slum upgrading programs are associated with meaningful climate adaptation benefits as an unintended consequence. Leveraging the staggered rollout of 31 interventions in Rio de Janeiro, Brazil, between 2006 and 2019, we employ a difference-in-differences design with fixed-effects Poisson models applied to daily mortality records across 806 healthcare facilities. We find that heatwaves increase mortality by 5.1% to 8.2%, and that proximity to slum upgrading interventions is associated with a 3.9%–5.5% reduction in this excess mortality, mitigating nearly half of the heatwave mortality penalty. Effects are concentrated in cardiovascular and respiratory causes of death, consistent with the biological pathways linking heat exposure to mortality. These findings have direct implications for the over 1.1 billion people residing in informal settlements, many in tropical regions where heatwave frequency and intensity are projected to increase under climate change, and suggest that large-scale infrastructure investment in slums should be recognized as a tool for climate adaptation in urban policy.