Planting just 20% more trees within city limits will add more than US$500 million in value for megacities like Buenos Aires, Los Angeles, and Tokyo, while improving the socio-economic, physical, and spiritual well-being of tens of millions of urban dwellers, according to a new study in the journal Ecological Modelling.

The dollar figure reflects the value of “pollution absorbed, temperatures lowered, and moisture taken up,” Climate News Network reports.

“By cultivating the trees within the city, residents and visitors get direct benefits,” said study co-author Ted Endreny, environmental resources engineering professor at State University of New York. “They’re getting an immediate cleansing of the air that’s around them. They’re getting that direct cooling from the trees, and even food and other products. There’s potential to increase the coverage of urban forests in our megacities, and that would make them more sustainable, better places to live.”

For inhabitants of megacities like Lagos, Nigeria and Karachi, Pakistan, the absence of the natural cooling that an urban forest provides can mean the difference between life and death during a heat wave. “Cities are afflicted by the notorious heat island effect,” Climate News Net notes, “and climate scientists have repeatedly warned that extremes of heat and humidity could rise to potentially lethal levels in many of the world’s great cities.”

But installing yet more mechanical (and chemical) air conditioning systems becomes a significant driver of emissions in its own right.

A paper in the journal Science by Sandra Díaz, professor of community and ecosystems ecology at Argentina’s Córdoba National University, adds “that a better understanding of the way nature—in the form of forests, wetlands, savannahs, and all the creatures that depend on the natural world—underwrites human well-being should inform political and economic decisions,” writes Climate News Net correspondent Tim Radford. That understanding, in turn, “would involve attending to the wisdom and experience of local communities and Indigenous people who depend more directly on nature’s riches.”  

Radford cites Sir Robert Watson, director of strategic development at the UK’s Tyndall Centre for Climate Change Research and chair of the Intergovernmental Platform on Biodiversity and Ecosystem Services, who pointed to the “greater riches” beyond economic calculus that come from such experiential wisdom.

“While nature provides a bounty of essential goods and services, such as food, flood protection, and many more, it also has rich social, cultural, spiritual, and religious significance—which needs to be valued in policy-making as well,” Watson said.