How Much Are Trees Worth to Megacities?

In a metropolis teeming with shuffling crowds, cranes and high-rises shouldn’t be the only things reaching skywards. Megacities—those urban centers crammed with more than 10 million people—would be well served to double down on their arboreal assets, according to a new paper in the upcoming issue of the journal Ecological Modeling.

A team of researchers led by Theodore Endreny of SUNY’s College of Environmental Studies and Forestry sought to quantify how leafy infrastructure pays dividends in 10 chock-full cities—and the extent to which the benefits could compound if those areas went greener.

To estimate the existing tree cover in Beijing, Buenos Aires, Cairo, Istanbul, London, L.A., Mexico City, Moscow, Mumbai, and Tokyo, the researchers adapted the i-Tree model, which was developed by the U.S. Forest service in 2006. i-Tree employs aerial photography to gauge the dollar value and environmental payoff of the urban canopy. To date, it’s only been used to snap a birds-eye-view of the canopy across U.S. cities (past analyses have zoomed in on L.A. and Austin).

In order to assume a more global perspective, the researchers spent several months crunching the numbers for London to arrive at estimates of trees’ contributions to air pollution removed, stormwater runoff avoided, energy left unguzzled, and carbon sequestered. Researchers then scaled these estimates and units for the various cities.

For each location, the researchers surveyed 500 randomly selected points, and characterized them according to their potential for leafy benefits. Each plot was categorized as existing tree cover, potential canopy—including spots currently serving as parking lots, plazas, or sidewalks—or surfaces that didn’t lend themselves to trees.

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