Urban trees aren’t just nice, scientists say — they’re mandatory

They tower overhead and sway in the wind and often teem with squawking birds, yet trees are easy to ignore. Urbanites rush by them without noticing, and without appreciating all the work they do: Trees reduce temperatures, mitigate flooding, and provide habitat for animals. City leaders are no exception to this oversight. As mayors around the world pledge to reduce municipal greenhouse gas emissions, they’re missing the literal low-hanging fruit of bolstering urban forests, dozens of scientists argue in a new essay. “We have to elevate it from something that is nice to have, to something that we require — like, mandatory,” said Manuel Esperon-Rodriguez, an ecologist at Bangor University in the United Kingdom and lead author of the piece, publishing today in the journal PLOS Climate. “In the same way that we treat education, security, transportation, it has to be elevated to that level.” What makes urban forestry so important? For one, trees significantly cool the concrete jungle, by providing shade and releasing water vapor to “sweat.” Patches of greenery also allow stormwater to soak into the ground instead of pooling and flooding — that investment alone will spare cities from economic damages as a warming atmosphere makes rain fall harder. Spending time in parks also boosts mental health, while urban farms produce nutritious food and create jobs. Planting trees, especially native species, also provides shelter and food for fauna. At the same time, vegetation absorbs pollutants, improving air quality for everyone. These scientists have laid out a four-point approach to funding, raising, and maintaining urban forests. This, by the way, includes individual trees on sidewalks, parks, and woodlands in cities. But it’s really about all the vegetation — not just trees but shrubs as well — within the city limits, whether that’s in someone’s backyard or growing in a street median. The first hurdle is investing in this stuff. Urban forestry isn’t just about buying a bunch o