News: A global study covering 761 cities across 105 countries (including India) reveals that urban greening does not always reduce heat. In dry and water-scarce cities, poorly planned vegetation can increase urban temperatures, creating a “Green Paradox”

Highlights:

• Nearly 25% of cities, mainly in low-rainfall regions (<1,000 mm annually), experienced net warming.
• Several Indian cities fall within this vulnerable category.

Key Features:

Urban Heat Drivers Identified:

• Global climate change
• Urban Heat Island (UHI) effect, where concrete and asphalt trap heat more than rural areas.

Metric Used – Temperature Regulation Capability (TRC):

• Defined as the temperature difference between vegetated surfaces and built-up surfaces.
• Negative TRC: Vegetation is cooler → cooling effect
• Positive TRC: Vegetation is warmer → warming effect

Green Paradox Explained (Dry Regions)

• Limited water availability reduces evapotranspiration, the main cooling mechanism of plants.
• Water-stressed vegetation:
• Absorbs more solar radiation
• Provides little evaporative cooling
• During heat stress and low humidity plants restrict water loss= sharply reducing cooling.

Concerns

• One-size-fits-all urban greening policies may–Worsen heat stress in arid and semi-arid cities, Increase water demand, Undermine Heat Action Plans
• Risk of misguided climate adaptation in water-scarce megacities.

Outcomes / Significance

• Need for climate-sensitive urban planning.
• Shifts focus from “more trees” to “right trees in the right place”.
• Helps optimize greening strategies for actual cooling benefits.