Why Indian Cities Need Smarter Greening Strategies

A new study reveals that Indian cities need smarter, climate-responsive urban greening strategies that consider humidity and ventilation to effectively combat heat stress.

Researchers at the Indian Institute of Technology, Gandhinagar, have found that urban greening alone is insufficient to reduce heat stress and that cities need more climate-responsive planning to maximise cooling benefits.

The study, published in Nature Communications, analysed 138 Indian cities between 2003 and 2020 across tropical savanna, semi-arid steppe and humid subtropical climate zones.

"A new study by Indian Institute of Technology Gandhinagar researchers found that while urban greening remains essential to reduce heat stress, cities need smarter and more climate-responsive planning to ensure that tree cover delivers maximum cooling benefits," the premier institute said in a statement on Monday.

Understanding the Impact of Vegetation on Cooling

Researchers found that the cooling benefits of vegetation can vary significantly depending on humidity, canopy density, urban compactness and airflow conditions.

The findings also carry "strong equity implications" as communities most exposed to dangerous heat often live or work in dense, poorly ventilated neighbourhoods with limited access to cooling infrastructure.

"Better-designed urban greening could help reduce long-term heat vulnerability for these populations," the statement added.

The Need for Tailored Greening Strategies

Corresponding author Udit Bhatia, Associate Professor at IIT Gandhinagar's Department of Civil Engineering, said one-size-fits-all plantation targets fail to address the full scope of the problem.

"Greening is essential for climate adaptation and shade gives people immediate relief. Our results show that one-size-fits-all plantation targets miss part of the problem. Cities need greening strategies that are designed for shade, moisture and ventilation together," he said.

Lead author Angana Borah, a research graduate at IIT-Gandhinagar, said the question was not whether cities should be green, but "what kind of green, where and how much".

"In dry cities, vegetation can provide strong cooling benefits. In humid and compact neighbourhoods, planners also need to think about airflow and moisture build-up," she said.

Integrated Urban Cooling Strategies

The study said Indian cities need integrated urban cooling strategies where shade trees, parks, roadside plantations, open spaces, and ventilation corridors are planned together.

Researchers reconstructed the "Heat Index", which combines temperature and humidity and better reflects how heat is experienced by the human body, instead of relying only on land surface temperature.

Using multiple satellite and urban datasets, including vegetation indices, canopy density measures, night-time light data, and Local Climate Zone mapping, the team generated one-kilometre Heat Index maps and applied explainable artificial intelligence methods to identify urban features associated with heat stress.

The study found that while vegetation cover and canopy structure were linked to lower Heat Index levels once greenness crossed certain thresholds, "very high canopy activity" in humid and densely built neighbourhoods was sometimes associated with increased Heat Index levels.

Balancing Shade and Moisture

The researchers said trees cool cities through both shade and evapotranspiration. In dry climates, evapotranspiration can significantly reduce heat because the surrounding air can absorb additional moisture. In contrast, in humid and compact urban areas, excess moisture can remain trapped near the ground, increasing humid heat stress despite local shade benefits.

The researchers said the study operates at a city-scale resolution and does not yet provide species-specific or street-level prescriptions.

"The study's central message is that trees remain indispensable for climate adaptation, but future-ready urban greening must go beyond increasing green-cover targets alone. Under hotter and more humid climate conditions, cities will need greening strategies that simultaneously provide shade, manage moisture and preserve airflow," the statement added.