Urban inequality, green infrastructure, and health system vulnerability to climate extremes in a tropical city

Flooding and landslides increasingly threaten urban public health systems, particularly in cities characterized by deep socioeconomic inequalities and fragile infrastructure. Using Salvador (Brazil) as a case study, this research examines how climate-related hazards, vegetation cover, and socioeconomic conditions interact to shape the spatial vulnerability of municipal health centers. We integrate geospatial analysis, environmental indicators (including the Normalized Difference Vegetation Index), socioeconomic data, and multivariate methods to assess exposure patterns across neighborhoods. The results reveal pronounced socio-environmental inequalities: health facilities located in low-income areas are disproportionately exposed to flood and landslide risks and are more frequently embedded in neighborhoods with inadequate sanitation and limited infrastructure. Although vegetation cover is associated with risk mitigation, higher NDVI values do not necessarily correspond to lower vulnerability. In several areas, elevated vegetation coincides with high landslide risk, reflecting the presence of unmanaged or poorly integrated green spaces on steep or environmentally fragile land. These findings highlight the need to distinguish between vegetated areas and socially functional green infrastructure within urban climate adaptation strategies. More broadly, the study demonstrates that climate vulnerability in cities emerges from the interaction of physical hazards, social inequality, and infrastructural governance, rather than from environmental factors alone. We argue that effective climate adaptation requires integrated urban governance linking green infrastructure, public health planning, and social equity to build healthier and more resilient cities in the Global South.