Trees and Londoners co-exist in a southeast suburb of the capital. Chris Ratcliffe/Bloomberg

Shady trees mean less air conditioning and increased worker productivity in the summer months.

London’s leafy streets and gardens have long been prized for their beauty — and more recently their ability to counteract carbon emissions and improve air quality. But the value of urban trees can also be measured with money. A new report from Britain’s Office of National Statistics estimates tree cover saved the capital more than 5 billion pounds ($6.56 billion) from 2014 to 2018 through air cooling alone. Additionally, by keeping summer temperatures bearable for workers, trees prevented productivity losses of almost 11 billion pounds.

The estimates underline just how vital the role trees play is in making cities comfortable and functional in a warming world — particularly in London. An unusually long, hot summer in 2018 pushed cost savings estimates to their highest level to date.  

Part of the study’s purpose is to promote planting trees and maintaining green spaces, according to Hazel Trenbirth, a member of the ONS' Natural Capital team, which looks at cost savings of greenery across the U.K.

“Britain’s trees have a value that goes far beyond what you can get from chopping them down,” she said.

Protecting existing urban trees can be more beneficial than planting new ones. // Matthew Lloyd/Bloomberg
The findings from the ONS echo a 2015 report partly funded by the London Mayor’s office, which found that the city’s 8.4 million trees removed an estimated 2,240 tonnes of pollutants (mostly ozone) from London’s atmosphere annually, a process that would otherwise have cost 126 million pounds. They sequestered carbon up to a value of 4.79 million pounds and saved the city 2.8 million pounds by alleviating storm water run-off.  

That economic benefits may remind authorities and businesses that a workplace surrounded by trees, located in a well-planted city, ultimately helps look after their bottom line. Still, not all trees are equal, and when it comes to cooling and carbon capture, the answer isn’t as simple as just planting more trees to replace older ones.

“Often when a heritage tree is threatened with removal, you hear, ‘We’re going to plant ten trees to replace it,’” says Phil Wilkes of University College London, author of a study mapping the carbon absorption of London’s trees. “But younger, smaller trees don’t absorb anything like the same amount of carbon, and five or ten years down the line they’re far easier to get rid of if someone wants the land for something else.”

The most obvious benefit of older trees is less measurable: natural beauty in an urban area. London’s woodlands are storied places — some of them continually planted since the Middle Ages — while the city’s residential neighborhoods are seamed with back gardens whose trees shelter bird and insect life. Altogether they shade 21% of the city’s area with their canopy. Even if these trees delivered no economic benefit at all, many city dwellers have plenty of reason to keep them alive.

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