The Magic of Tree-Lined Streets

It’s time to talk about trees.

Why?  Because I live in Tulsa, Oklahoma, where it’s currently 96 degrees Fahrenheit with 50% humidity, resulting in a heat index of 109 degrees. This is just a scientific way to say that it’s hotter than hell-fired habaneros out there.  And to be frank, nobody cares about walkable urbanism when they’re sweating through their clothes. 

Mad Dogs and Englishmen Go Out in the Midday Sun…

No place for humans. (Photo by Sarah Kobos.)

A few days ago, despite the soaring temperatures, I decided to run a couple errands.  Since both trips were within a mile and a half of my house, I hopped on my bike.  For the first mile or so, I was able to cut through neighborhoods where mature trees shaded my route.  With the shade and a nice breeze, the ride was amazingly comfortable.  “This isn’t so bad,” I thought, casually dismissing all the heat warnings I’d heard earlier in the day.  

Unfortunately, my sanguine attitude evaporated the moment I emerged from the sanctuary of a shaded neighborhood into a treeless, asphalt furnace.  

No disrespect to Joan of Arc, but at least if you get burned at the stake, it’s a dry heat.  This was more like being boiled.  And then fried.  If you built a sauna inside a kiln, it would feel something like this street.  

A Hostile Walk Environment

The only thing worse than biking on a treeless street on a scorching hot day is walking on one.  Since cycling creates its own breeze, you get some relief through evaporative cooling.  You also reach your destination faster, which minimizes the agony.  Without trees, walking along a typical city street in the summer heat is not only unpleasant, it can be life threatening.

So when you talk about “complete streets” and “active transportation” be sure to mention the importance of canopy trees.  Because in a hot climate, if you don’t have shade, these options are moot.  Everyone with a car is going to drive.  Everyone without a car is going to suffer, or stay home.

And if you’ve never thought about street trees as a social justice issue, an afternoon spent in the summer sun walking to (and waiting for) the bus might just change your mind.

Street trees along a Mexico City boulevard offer respite from the afternoon sun. (Photo by Sarah Kobos)

Simply put, trees matter.  And I don’t mean those shrubs people stick in parking lots to fulfill the landscaping requirements of the zoning code.  I mean real trees.  The kind that line sidewalks and create canopies over the street.  The kind that turn inhospitable environments into pleasant places for people.

The Decline and Fall of the Urban Street Tree

Tulsa street trees in 1950. (Photo courtesy of the Beryl Ford Collection)

Our ancestors, who hadn’t yet invented air-conditioning or automobiles, understood this.  They knew that city building and tree planting went hand in hand.  Thus, long before the introduction of zoning codes, cities passed laws requiring trees to be planted along the public rights-of-way.

Unfortunately, here in Tulsa, our urban forest has suffered in recent decades.  In my lifetime alone, a number of tragic events—both man-made and natural—have decimated our once dignified tree-lined streets.  Dutch Elm Disease, wind storms, ice storms, and butchering by unqualified tree-trimmers—many hired by the local electric company to protect power lines—have destroyed countless thousands of mature trees throughout the city.

Not everyone has re-planted.  Many people simply don’t relish dealing with them after the expensive ordeal of removing massive downed trees from their property.  (I don’t know if a tree makes a sound when it falls in the forest; but when it crushes your roof, it leaves a lasting impression.)  Some can’t afford the luxury of replanting.  Others, like many rental property owners, just don’t bother.  And those with the inclination and financial resources to replant may select an inappropriate species or ineffective location for their replacement trees.  

A neighborhood looks naked without street trees. Photo by Sarah Kobos

When it comes to creating tree canopies, many obstacles are enshrined in public policy.  Zoning codes apply to private property, not the city’s right-of-way, so required trees are often set back too far from the street to create a pleasing pedestrian environment.  Engineering standards require clear sight lines next to the road, which prevents street trees from being located where they are most effective.  And the local power company recommends planting short, ornamental trees near power lines, which, all too often, are located along arterial streets.  Together, these rules eliminate the possibility of creating or restoring a tree canopy that would benefit pedestrians and cyclists throughout the city.

Beyond Pedestrian Comfort: Street Trees and the Bottom Line

We have a long way to go to replace what has been lost.  But we have to keep working because street trees make places more walkable and bikeable and beautiful.  All of which should be reason enough to fight for better streetscaping.

But there are myriad other ways in which street trees benefit cities and individuals alike. Among the most important to municipalities are significant reductions in stormwater runoff; improved air quality and reductions in greenhouse gases like ozone and carbon dioxide; improved pedestrian and driver safety; and higher taxes resulting from increased property values and commercial sales.  

Street trees working their magic in Tulsa, OK. Photo by Daniel Jeffries

To achieve these benefits, we need to take trees seriously.  Especially in urban areas, you can’t just stick a tree in the ground and expect it to prosper.  For cities interested in maximizing their return on investment of street trees, the EPA has created a guide focused on design considerations that will allow street trees to survive and thrive well into maturity.

Whether you care about the environment, energy savings, property values, public health, or your city’s bottom line--plant a tree by the street.  You’ll make sweaty cyclists and pedestrians happy for generations to come.

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