Story at a glance

  • By some estimates, Tampa, Florida and New York City are the cities with the most tree cover.
  • Urban trees provide health and environmental benefits, absorbing pollution and reducing heat islands.
  • "If we show you a map of tree canopy in virtually any city in America, we're also showing you a map of income," says one expert.

Urban trees offer a lot of benefits to city-dwellers, from absorbing air pollution, to providing shade, to raising property values. Now, researchers are using satellite photos and artificial intelligence to calculate which cities have the most tree cover and how cities with sparse tree cover can learn from their greener counterparts.

Multiple organizations are trying to quantify urban tree cover, The Guardian reports. Researchers at MIT’s SENSEable City Lab developed ‘Treepedia,’ which launched in 2016 and uses Google Street View photos and an algorithm to count the trees on the streets of 27 cities worldwide. The researchers found that Tampa, Florida has the most street tree cover at about 36 percent, followed by Singapore; Oslo, Sweden; and Vancouver, British Columbia.

But the U.S. Forest Service, which is using satellite imagery to calculate the sizes of urban canopies, found that New York City has the most trees with more than 39 percent. The MIT team put NYC at only 16.6 percent tree cover, but because they were focused on the trees that line city streets, they didn’t count Central Park. The two studies looked at different cities (the U.S. Forest Service studied the single most populated urban area in each of 25 countries) and used different data sources, for example the satellite imagery being used by the U.S. Forest Service is from between 2010 and 2014, according to The Guardian.

“We are seeing a surge in attention around urban trees around the world…not just because they are beautiful, but because cities realize that trees are an important part of resiliency, health, wellness, happiness, economic benefit — the list goes on,” Dan Lambe, president at the charity Arbor Day, told The Guardian.

Cities are now making concerted efforts to increase their tree cover. In 2015, New York finished a project to plant 1 million trees, and in Singapore, any new road projects must include planned space for trees on either side. Trees are particularly important for reducing urban heat islands, but research has shown that lower income areas of cities most often lack trees. NPR reported in September that wealthier areas of Louisville, Ky., have up to double the trees of lower-income neighborhoods.

And programs to expand tree cover in cities to neighborhoods that lack it need to be cognizant of history, as environmental activists found when trying to start a tree planting program in Detroit. City Lab reports that the planting program faced pushback rooted in distrust that the city would properly maintain the trees, and lack of proper community outreach by the advocates. 

"If we show you a map of tree canopy in virtually any city in America, we're also showing you a map of income," Jad Daley, president and CEO of the nonprofit American Forests, told NPR. "And in many cases, we're showing you a map of race and ethnicity."

Published on Nov 12, 2019