Acre For Acre, Urban Trees Can Store As Much Carbon As Tropical Forest

Sourced from Anthropocene Magazine

Trees lining city streets, in public and private gardens, in parks, and in patches of urban woodland do a lot for cities. They help mitigate air pollution, lessen the urban heat island effect, provide flood control, and contribute a host of other benefits. Some studies have valued these ecosystem services at almost USD $1 million per square kilometer per year.

And it turns out that these trees, collectively known as the urban forest, also contribute more than you might imagine to carbon sequestration, according to a new study published in the journal Carbon Balance and Management.

Researchers from University College London used a laser-based remote sensing method called LiDAR to build an intricately detailed 3D picture of more than 84,000 individual trees in their home borough of Camden, in northwest London. Then, based on the volumes of trunks and crowns, they calculated the amount of carbon each tree stores.

“We were able to map the size and shape of every tree in Camden, from forests in large parks to individual trees in back gardens,” lead author of the study and University College London geographer Phil Wilkes said in a press release. “This not only allows us to measure how much carbon is stored in these trees but also assess other important services they provide such as habitat for birds and insects.”

Wilkes and his colleagues pioneered this method in tropical forests, but they had to calibrate it anew to apply it to urban trees. That’s because tree crowns can grow very differently in open parks or street canyons than they do in closed-canopy forest. In addition, urban trees tend to encounter unique conditions such as exposure to car exhaust, extra water from irrigation, trimming to avoid contact with buildings and power lines, and so on.

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