Strategically placed greenbelts in the suburbs could cool some of the world’s biggest cities by almost half a degree across at least half their area, according to a new analysis.

The findings suggest an old but often overlooked strategy to manage the urban heat island effect, the tendency for cities to be a few degrees hotter than surrounding landscapes due to their extensive pavement, concrete and steel buildings, and lots of people packed together.

In recent years, many cities have tried planting trees to help mitigate heat. But some are still sweltering through increasingly warm summers. The new study suggests a solution might be found outside the cities themselves.

“For urban cooling, where we place vegetation can be just as important as how muchvegetation we have,” says study team member Shi-Jie Cao, director of the Center for Sustainable Built Environment at Southeast University in Nanjing, China.

Cao and his collaborators were inspired by an urban planning pattern characteristic of traditional Chinese villages known as the mountain-water-forest (MWF) framework, in which “settlements are backed by mountains, facing water bodies, and are embedded within surrounding forests,” the researchers write in Nature Cities.

The team set out to explore whether this approach could also apply to today’s large, heterogeneous metropolises. They used a computer model to gauge how temperatures in the urban core on a hot summer day would be affected if suburban areas upwind of a city were converted to either woodlands or built-up areas.

The strategy could help cool both Beijing, a city built on a plain at the base of mountains, and Shanghai, located on the coast, the researchers found. Analysis based on these two cities revealed the mechanisms involved: first, the suburban vegetation creates a cool mass of air, and then prevailing winds sweep the cooler air from the suburbs into the city.

The researchers then analyzed six additional mega cities—Cairo, Kinshasa, São Paulo, Houston, Sydney, and London—to see how widely applicable the approach might be. “One of the most striking results was how robust the basic cooling mechanism was across cities with very different climates, topographies, and urban forms,” Cao says.

Across the eight cities, the upwind greening approach could reduce temperatures on a hot summer day by an average of 0.4 °C across at least half the city area. The exact magnitude, timing, and spatial extent of the cooling varied from city to city, “but the underlying pathway—creating cooler air upwind and transporting it into the city—remained remarkably consistent,” says Cao.

The analysis shows not just the potential but the limits of the strategy. The cooling effect is more modest and localized in Shanghai than in Beijing because Shanghai’s cooling sea breezes don’t align perfectly with the locations where suburban trees could be planted.

“This is not simply a call to plant more trees everywhere,” Cao says. “The strategy works best where cities have relatively persistent wind pathways and sufficient space for greening on the upwind side.”

Of course, that space for suburban greening might already be taken up by houses, roads, and industry, so creative approaches to creating multi-functional landscapes—and getting local governments and others stakeholders on board—will be necessary.

But the real lesson from traditional village design is a more general one, Cao says: “We hope the study encourages cities to think beyond isolated green spaces and consider vegetation, wind, topography, water, and the surrounding landscape as an interconnected climate-regulation system.”

Source: Yang M. et al. “Overlooked upwind greening for urban cooling.” Nature Cities 2026.