Urban trees provide valuable services to megacities and their residents, including environmental and financial benefits, that are estimated to be worth over $500 million a year, according to research from the College of Environmental Science and Forestry (ESF) in Syracuse, New York.

Looking at 10 megacities—Beijing, China; Buenos Aires, Argentina; Cairo, Egypt; Istanbul, Turkey; London, Great Britain; Los Angeles, United States; Mexico City, Mexico; Moscow, Russia; Mumbai, India; and Tokyo, Japan—researchers determined that trees help to reduce pollution, stormwater runoff and carbon emissions, in addition to keeping the heating and cooling costs of buildings lower thanks to the coverage the trees provide.

"Megacities can increase these benefits on average by 85 percent," said the study's lead author, Dr. Theodore Endreny of ESF. "If trees were to be established throughout their potential cover area, they would serve to filter air and water pollutants and reduce building energy use, and improve human well-being while providing habitat and resources for other species in the urban area."

"Trees have direct and indirect benefits for cooling buildings and reducing human suffering during heat waves," Endreny continued. "The direct benefit is shade which keeps the urban area cooler, the indirect benefit is transpiration of stormwater which turns hot air into cooler air."

Another, lesser-known benefit of urban tree coverage includes the protection offered by leaves that collect dangerous airborne particulate matter.

"Placing these results on the larger scale of socio-economic systems makes evident to what extent nature supports our individual and community well-being by providing ecosystem services for free," said one of Endreny's co-authors, Professor Sergio Ulgiati of University Parthenope of Naples, Italy. "A deeper awareness of the economic value of free services provided by nature may increase our willingness to invest efforts and resources into natural capital conservation and correct exploitation, so that societal wealth, economic stability and well-being would also increase. As a follow-up of this joint research, we have created in our university an Urban Wellbeing Laboratory, jointly run by researchers and local stakeholders."