Cities Can’t Afford to Keep Treating Trees Correctly

Stand under a big old tree on a sweltering afternoon and you’ll understand something city planners are only now starting to take seriously: that shade isn’t decoration. It’s doing a job.

Trees are cooling the block, catching stormwater before it floods the street, and scrubbing pollution out of the air a person’s actually breathing.

A new study, written by more than 60 scientists spanning dozens of countries, makes the case that most cities still can’t quite bring themselves to treat trees like the infrastructure they clearly are.

The team behind it is led by Manuel Esperon-Rodriguez from Western Sydney University and Bangor University, with Mark G. Tjoelker from Western Sydney University as senior author.

Trees need time to grow

You can plant a sapling in twenty minutes. Growing an actual canopy, the kind that meaningfully cools a neighborhood though, takes decades.

So when a mature tree comes down, a city doesn’t just lose a tree. It loses thirty or forty years of accumulated shade, habitat, and carbon storage, and there’s no fast way to buy that back.

And yet trees keep losing these fights. Developers clear them because it’s cheaper and faster and penalties for illegal removal are often too weak to sting.

City budgets tend to fund the planting photo-op but not the years of watering, pruning, and pest management that actually keep a tree alive.

The researchers want stiffer enforcement, real tax incentives for landowners who keep mature trees standing, and minimum canopy requirements written into law rather than left to goodwill.

They even suggest big infrastructure projects, the kind that usually flatten everything in their path, could be redesigned to grow canopy instead of erasing it.

Not every neighborhood gets the shade

Wealthy neighborhoods, almost everywhere researchers have looked, tend to be noticeably leafier than poor ones.

Meanwhile, it’s the low-income neighborhoods that usually catch the worst of the heat and the dirtiest air.

The trees, in other words, tend to show up exactly where they’re needed least.

Closing that gap takes more than a citywide average that quietly hides the worst blocks.

Greening neighborhoods without displacing residents

The authors want targets set neighborhood by neighborhood.

They also want the people who actually live there, including Indigenous communities, involved in deciding what gets planted and where – rather than having greenery imposed on them from a planning office.

There’s a warning too: planting lots of trees without a plan can trigger green gentrification, raising rents and pushing out the very residents the trees were meant to benefit.

The only real fix, the researchers argue, is tying tree policy directly to housing policy instead of treating them as two separate departments that never talk.

Trees barely show up in climate policy

Given how much trees do, it’s almost strange how absent they are from the major climate and biodiversity agreements that actually move money and political will.

The authors want that fixed, with urban forests written explicitly into national climate plans, biodiversity strategies, and the commitments countries make under frameworks like the Paris Agreement.

Money remains the sticking point. Estimates put the global price tag for nature-based climate solutions, urban forests among them, at well over $500 billion a year.

Most current funding covers the ribbon-cutting moment of planting a tree and stops right there, leaving the decades of upkeep that actually determine whether that tree survives unfunded and, often, forgotten.

The study points to newer tools like green bonds, biodiversity credits, and tracking programs such as Tree Cities of the World as ways to start closing that gap, rather than continuing to fund trees like a one-time expense.

Many cities fail to keep record of trees

Maybe the most surprising finding here isn’t political, it’s logistical. Plenty of cities simply don’t keep good records on their own trees.

Nobody’s tracking which newly planted saplings actually survive their first few summers, which species are struggling, or how unevenly canopy is spread across town.

Without that information, cities are essentially guessing whether their tree policies work at all.

The scientists push for cheaper, sharper tools, satellite imagery, AI-assisted monitoring, to close that data gap, especially for less rich cities.

City trees should be diversified

The team also flags a quieter risk: planting the same few species block after block. It looks tidy, but it’s fragile.

One well-timed pest or disease can wipe out an entire city’s canopy in a single outbreak.

Instead, the researchers argue that cities should diversify their tree populations. Non-native species can be included where they are well suited to a hotter, drier future.

At the same time, cities should continue prioritizing native trees while respecting the ecological and cultural context of each place.

An urgent problem

A city’s trees aren’t a nice-to-have thing that gets funded once the “real” priorities are covered.

They’re already doing the work of public health policy, climate defense, and neighborhood fairness, whether or not anyone’s paying for it that way.

The authors don’t treat this as a distant problem. Cities keep growing and heatwaves keep getting worse.

Thus, the decisions being made right now – about which trees get to stay standing and which neighborhoods get to keep their shade – will quietly decide how livable those cities feel for decades after the people making those decisions are gone.

The study is published in the journal PLOS One.

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