Simply increasing tree cover does not always make cities cooler. In humid urban areas, dense tree canopies can even raise the Heat Index by trapping moisture. This is according to a new study published in Nature Communications and highlighted by a Mongabay-India (MI) report. Titled ‘Dense canopies reverse the cooling effect of urban greening in humid cities’, the study’s abstract points out that urban greening is widely promoted as an adaptation strategy to cope with rising heat stress; however, its effectiveness remains uneven, especially across rapidly warming cities of the Global South. Vegetation can cool urban environments but can also intensify humidity and thermal discomfort, raising questions about when green adaptation succeeds or backfires. The study assesses how vegetation structure and function influence the Heat Index (HI), a humidity-adjusted measure of perceived heat, across 138 Indian cities spanning diverse climates. Findings indicate that green adaptation can shift from a cooling asset to a humid-heat liability under some conditions, underscoring the need for climate-responsive and equitable design strategies in the Global South. The cooling benefits of urban trees depend on a combination of canopy structure, photosynthetic activity, local climate, urban density and airflow, rather than tree cover alone, says the MI report. It adds that researchers argue that urban greening must be climate-smart, prioritising the right tree species, the right locations and thoughtful planting design over simply planting more trees. Instead of looking only at air temperature or land surface temperature, the study focused on the HI which is the “feels like” temperature that combines heat and humidity because humans respond to both temperature and moisture in the air. The study finds that while urban trees generally help cool cities by providing shade, reducing incoming solar radiation, and lowering surface temperatures, these benefits vary in different cities. In humid cities, dense