Why Do We Need Tree Canopies in Our Urban Areas?
The Environmental, Economic, and Social Benefits of Trees
“Why are tree canopies in urban areas important?”
With more studies and educational materials become available, we probably have all agreed that trees offer many environmental benefits: such as reducing erosion, helping stormwater management, providing shade and absorbing pollutions, etc.
Trees also have other benefits to the triple bottom line: Environmental, Economic, and Social aspects of our life.
But today, I would like to share another perspective to look at those trees in our neighborhoods.
Tree Coverage vs. Neighborhood’s Prosperity
“Trees are not merely good for us; they bring out good in us.”
See images below. What would you like to see when you look outside?
Trees and Neighborhood’s Happiness
A study, “Aggression and Violence in the inner City,” done by professors Ming Kuo and William C Sullivan, proved a positive impact of green spaces on our well-being. While they investigated residents’ behavior in a neighborhood on the southern side of Chicago, they found out:
“Residents living in ‘greener’ surroundings report lower levels of fear, fewer incivilities, and less aggressive and violent behavior. And residents living in relatively barren buildings reported more aggression and violence than their counterparts in greener buildings. Moreover, levels of mental fatigue were higher in barren buildings, and aggression accompanied mental fatigue.”
Trees as Neighborhood’s Income Indicator
Moreover, recent studies also show the tree coverage associated with the neighborhood’s income inequality. For example, the District of Columbia’s wealthiest neighborhood has 42 percent more tree coverage than destitute neighborhoods.
The reasons for this phenomenon are complex, yet researchers suspect that people who own their homes are more likely to take care of their trees than renters and more likely to lobby their governments to plant or maintain trees at places close to their homes. They are also more educated to embrace tree planting since they understand what benefits trees can provide. On the other hand, residents who make fewer wages and often commute longer distances are less likely to take care of their surroundings.
My Tiny Discovery
I was curious if this “tree coverage indicates neighborhood stability” could be applied to any place. Thus, I explored the web tool iTree and collected the tree coverage data in these four neighborhoods: Four Corners, Hillandale, Silver Spring, and Adelphi.
Combining iTree’s data with the recent census data, which I summarized in the table below, you can see there is a correlation between the tree coverage and median household income. It also shows higher tree coverage has a lower crime rate. And interestingly, the capital beltway (I-495) seems to divide these neighborhoods into slightly affluent and somewhat impoverished areas.
A Question for Myself
You might argue my small number of samples cannot give an overall trend. But I still want to ask, “Will our neighborhood’s formula similar to the fate of Ida B Well Housing Project?”
- When a neighborhood has lower income:
- fewer trees are planted and maintained>>
- more aggressive behavior occurs>>
- more social problems arise in the community>>
- the neighborhood’s value drops>>
- more geographical turnover.
I wonder if reversing this formula also works in our neighborhoods?
- To avoid geographic turnover:
- plant more trees>>
- less aggressive behavior and less violence occurs>>
- neighborhood’s value rises>>
- more trees are planted and maintained>>
- residents are more pleased and stay longer>>
- neighborhood’s income stabilized and rises.
Will these trees be a powerful catalyst, like those magic painting murals that bring a barren place to live?
By the way, here are some actionable advice from the sustainable principles.
Prioritizing Tree Planting, Started with Conservation
Sustainable SITES has set up a decision-making hierarchy when we begin to look at a project site: Conserve > Manage> Restore> Generate.
There is also a guideline to refer to when we try to get the project’s sustainable credits. Available credits are:
[Sustainable SITES] Credit 4.8: Optimize Biomass
Conserve and restore vegetation biomass on-site to a level appropriate to the site’s region. A biomass density index (BDI) value is needed to determine the existing and proposed vegetation density. For example, trees with understory can get 6 (the most) biomass density values than the rest of the vegetations. The calculation as follow:
Biomass Density Value x Percent Total Site Area = BDI
[LEED Neighborhood Development] Credit: Tree-Line and Shaded Streetscape
Following these requirements could help the project earn points.
Option 1: Provide trees at intervals of no more than 50 feet long at least 60%of the total existing and planned block length within the project and on the project side of blocks bordering the project, between the vehicle travel and walkways.
Option 2: Provide shade from trees or permanent structures over at least 40% of the total length of existing and planned sidewalks within or bordering the project. Trees must provide shade within ten years of landscape installation. Use the estimated crown diameter to calculate the length of the sidewalk shaded.
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