An Urban Forest

As you head for home on a hot summer day, you turn off the loud blistering stretch of concrete that’s Piedmont Road into the neighborhood.  The shade of the tree canopy welcomes you, the temperature drops noticeably, it’s quieter, and you think how glad you are that you live here.  In fact, one of the main reasons you do live here is because it is an urban forest.

Urban forests are important to our quality of life and mental health; they are our contact with nature.  Every day in the neighborhood we see joggers, people on a stroll, dog walkers and bicyclists.  No need to convince you exercise is  better here than in a gym;  you already know it.

It’s the trees that provide the background for this setting.

Why Urban Trees Are Important

Wildlife – This website is all about urban wildlife, so we could talk about how important trees are to wildlife for a long time.  Instead, we put together the following 2-minute video that shows just a small number of the birds and critters that live with us and depend on trees.

Water Management – Trees and forests reduce stormwater runoff by capturing and storing rainfall in the canopy and releasing water into the atmosphere through evapotranspiration. In addition, tree roots and leaf litter create soil conditions that promote the infiltration of rainwater into the soil. This helps to replenish our groundwater supply and maintain streamflow during dry periods. [8]

Consider these facts:

• In one day, one large tree can lift up to 100 gallons of water out of the ground and discharge it into the air. [9]
• For every five percent of tree cover added to a community, storm water runoff is reduced by approximately two percent.  [10]

AS you watch the video below, imagine all of the water from this thunderstorm falling on impervious surfaces instead of the trees and leaf litter below the trees.  Plus, it’s much more pleasing to watch and be a part of.

Over 10 years ago, we worked with a developer  to save several old growth hardwoods on Timm Valley.  This builder saw the value of these trees and agreed that they made his property worth more.  Before his houses were even finished, the City of Atlanta came in and cut them down to put in a storm drain!

Air Quality – Hack! Gag! Cough!  That’s summer in Atlanta.  Although Atlanta’s air quality is improving, you can still smell the air and some days you can even see it.

Trees breathe in carbon dioxide and breathe out oxygen.

Oxygen production is one of the most commonly cited benefits of urban trees.  An acre of trees (100% tree canopy) can provide enough oxygen for 8 people.  However, ecology textbooks reveal that the vast majority of oxygen-producing organisms in the world are aquatic. [10]

It turns out that the relative impact of urban forests is more important for reducing carbon dioxide than for creating oxygen. Because small changes in air pollution concentrations can have relatively considerable impacts on air quality and human health, the effects of urban forests on air pollution can be significant. [10]

Also, older trees have a much bigger impact on air quality.  A 2002 USDA Forest study states that trees greater than 30 inches in diameter remove 70 times more air pollution than a small healthy trees that are 3 inches in diameter. [3]

Our mature urban forests then make a big difference in the quality of the air we breathe.

Buffer from Noise – Ever notice that when the leaves are off the trees in the winter this neighborhood is louder?  Noise coming from the train, MARTA, GA 400 and Piedmont road all seem to increase.  That’s because leaves have lots of surface area that baffle the sound.  Much like going to a restaurant where there is sound deadening material, like  acoustic tiles or fabric.

Trees are excellent at reducing the noise level.  Greenspace has the ability to mitigate noise in urban areas. Planting “noise buffers” composed of trees and shrubs can reduce noise by five to ten decibels for every 30m width of woodland, especially sharp tones, and this reduces noise to the human ear by approximately 50%. [11]

The folks on Darlington Commons had the right idea when they planted a row of Leyland Cypress  to help with noise from MARTA and the train.  Not only is their now mature row of trees dense, but the there’s a lot of surface area in the foliage.  And, these trees are evergreen, so they provide a noise reduction buffer all year.

Energy Savings – We know people in this neighborhood who have allowed a large, deciduous tree close to their house to be removed.  We’ve wondered how long it takes to realize that the reason their electricity bill in the summer months has skyrocketed is because all of the shade and evaporative benefits of the tree have also been removed.

Trees can also reduce energy use for heating by blocking cold winter winds.   Effective windbreak trees have crowns that extend to the ground and branches that keep their foliage in winter (evergreens).   Junipers, spruces, firs, Douglas-fir, and evergreen shrubs are good choices for wind protection.  [12]

Large old growth hardwoods and large evergreen pines were removed by a builder from a lot recently.  The before and after pictures are shown above.  Not only was this to the detriment of the new house being constructed, but the existing houses on either side will be impacted with higher energy costs as well.

Property Value –  It should be no surprise that trees increase property values.  Dr. Kathleen Wolfe with the University of Washington, College of the Environment, School of Environmental Science has published a document titled City Trees and Property Values.  In it she writes: “Although there have been a few exceptions, homes with trees are generally preferred to comparable homes without trees, with the trend across studies being a price increase of about seven percent.” [14]

She goes on to acknowledge that developers complain that preserving trees make development costs prohibitive.   This chart shows the results of a study showing the market price of treed vs. un-treed lots:

She concludes by saying “Given increased lot and home valuations, builders have reported that they were able to recover the extra costs of preserving trees in a higher sales price for a house and that homes on wooded lots sell sooner than homes on un-wooded lots.” [14]

Consider that an individual property value might increase even more if the property  is surrounded by other lots with ample tree cover. One of our neighbors writing on the neighborhood social media site said it best:

“One of the reasons we moved here was the green feel and the stunning trees in many yards.”

In other words, in an urban forest, the value of the whole just might be greater than the sum of the parts.  That only works if the whole urban forest is protected.

Trees In Your Yard

Tree Identification – It’s fun to learn what trees there are in your yard.  Many are quite old and have seen a lot.  Some are evergreen and some are deciduous.  Some are native and others are non-native.    If you are trying to identify a tree, we provide some help with a list of trees commonly seen in Peachtree Park.  We are always adding information to this list.

You can also get identification help from great websites such as the University of Georgia’s Extension Service, Lady Bird Johnson Wildflower Center and the Missouri Botanical Garden.

Size, Age and Special Status – We have a page with information that may help determine your tree’s size and age.

Also, some trees carry special status and may be deserving of recognition.  Find out about these special trees.

Planting a Tree

If you are thinking of planting a tree, we’ve put together a recommended list of Trees for Your Yard.  You can also learn about the importance of natives.

If you live in Peachtree Park or any part the City of Atlanta, Trees Atlanta offers up to 3  free yard trees for your front yard, and they will plant them for you.

Tree Stewardship

Unlike their counterparts in natural settings, urban forests exist and are maintained only through human intervention. [6]

References and Additional Information

[1]  Downtown Tree Management Plan – City of Atlanta, Georgia
[2]  Atlanta Urban Tree Canopy (UTC) study – Georgia Tech Center For Geographic Information Systems
[3]  The Effects of Urban Trees on Air Quality – David J. Nowak, USDA Forest Service
[4]  How Trees Can Retain Stormwater Runoff – Dr. James R. Fazio
[5]  American Forests: Tree Protection Toolkit
[6]  American Forests: Urban Forests
[7]  Trees Atlanta
[8]  Watershed Forestry Resource Guide: Reducing Stormwater Runoff
[9]  Keep Indiana Beautiful, Inc.:  Benefits of Urban Trees
[10]  Oxygen Production by Urban Trees in the United States: David J. Nowak, Robert Hoehn, and Daniel E. Crane
[11]  Forest Research: Benefits of Greenspace – Noise Abatement
[12]  Utah State University: Planting Trees For Energy Conservation: The Right Tree in the Right Place
[13]  HGTV: Increase Your Home’s Value With Mature Trees
[14] City Trees and Property Values – Kathleen L. Wolfe