Researchers Finding Evidence of the Negative Impacts of Trees in Urban Settings

More and more evidence has emerged in recent years about the many benefits of trees in urban environments. Every now and then, however, a study finds evidence that tress might not always be as benevolent as they seem.

2 minute read

November 11, 2015, 10:00 AM PST

By James Brasuell @CasualBrasuell


Trees and People

WDG Photo / Shutterstock

Rob MacKenzie shares insight into new research that might complicate assumptions about the role of trees in urban environments. The problem, writes MacKenzie: "some recent studies have suggested that trees may in fact worsen urban air quality by trapping pollutants at street level."

It's not that simple, of course, and Mackenzie insists that a closer look at the evidence "can help us come to a more nuanced understanding of the impacts of trees on our urban environment."

It all has to do with effect of the cocktail of buildings, structures, and landscapes that make up the city, of which trees have a unique role to play. "Trees affect the urban environment in several subtle ways. From altering air flows, to collecting pollution deposits, to affecting the chemical make up of the atmosphere, their impacts are both pervasive and difficult to pinpoint," writes MacKenzie.

So while MacKenzie goes into more detail about the several different pollution processes tress take part in, no studies have so far managed to put all the pieces of a city together. In lieu of a comprehensive model, MacKenzie uses the article as an opportunity to suggest strategies for piecing together different studies to create a more complete picture.

For more on the complex questions posed by the role of trees in the urban environment, an earlier article by John Gallagher first raised some of the same discussion points.

Tuesday, November 3, 2015 in The Conversation

portrait of professional woman

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching. Mary G., Urban Planner

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching.

Mary G., Urban Planner

Cover CM Credits, Earn Certificates, Push Your Career Forward

Logo for Planetizen Federal Action Tracker with black and white image of U.S. Capitol with water ripple overlay.

Planetizen Federal Action Tracker

A weekly monitor of how Trump’s orders and actions are impacting planners and planning in America.

July 2, 2025 - Diana Ionescu

Aerial view of town of Wailuku in Maui, Hawaii with mountains in background against cloudy sunset sky.

Maui's Vacation Rental Debate Turns Ugly

Verbal attacks, misinformation campaigns and fistfights plague a high-stakes debate to convert thousands of vacation rentals into long-term housing.

July 1, 2025 - Honolulu Civil Beat

White and purple sign for Slow Street in San Francisco, California with people crossing crosswalk.

San Francisco Suspends Traffic Calming Amidst Record Deaths

Citing “a challenging fiscal landscape,” the city will cease the program on the heels of 42 traffic deaths, including 24 pedestrians.

July 1, 2025 - KQED

Blue and silver Amtrak train at small station.

Amtrak Rolls Out New Orleans to Alabama “Mardi Gras” Train

The new service will operate morning and evening departures between Mobile and New Orleans.

July 3 - New Orleans City Business

Large spinning swing ride at Chicago's Navy Pier.

The Subversive Car-Free Guide to Trump's Great American Road Trip

Car-free ways to access Chicagoland’s best tourist attractions.

July 3 - Streetsblog Chicago

Aerial view of downtown San Antonio, Texas at night with rotating Tower of the Americas in foreground.

San Antonio and Austin are Fusing Into one Massive Megaregion

The region spanning the two central Texas cities is growing fast, posing challenges for local infrastructure and water supplies.

July 3 - Governing