Urban Trees = Nature’s AC

Thumbnail image for Jun10 292.jpgby Kathy Jentz


Those two weeks in June when we hit record high temperatures, were you feeling. “Hot Hot Hot” as Buster Poindexter sings? Walking around our local neighborhoods during that scorching month, I notice an odd phenomenon. Some streets are shady and cool, but others were as exposed and baking as Death Valley. What gives? Why are some yards full of healthy trees while others on the same block practically denuded of any plant life?


I started to think about those inside their homes cocooned in their air-conditioned world, oblivious to what those passing by their homes were dealing with on the naked sidewalks. I looked at their dark, asphalt shingle roofs absorbing all the rays of the sun with no trees or shrubs to filter and buffer the home. I bet they are not looking forward to receiving their next energy bill!


A few years ago  I attended the “Green Matters” symposium at Brookside Gardens in Wheaton, MD, homeowners and professional landscapers gathered to learn all about trees and their use in our lives and landscape. “Urban Re-Leaf” was the official name of the program and it centered greatly on trees in urban settings. Lest you be laboring under the mistaken assumption that you live in the suburbs, think again. In-fill development, disturbed soils, air pollution, surface compaction, etc. are stressing your trees and the tree canopy, just as they are in the inner city.


The day started off with an inspirational talk by famed photographer, James Balog. He featured images from his book Tree: A New Vision of the American Forest. Balog is passionate about nature and not separating ourselves from the real world by getting caught up in artificial media and pastimes.


“DC’s trees filter out 540 tons of harmful air pollutants per year,” according to Mark Buscaino, executive director of Casey Trees Endowment Fund. Mark also told us, “DC’s trees also give us $26 million in annual air conditioning savings.” Trees provide stormwater mitigation. They also offer direct economic and quality of life benefits. For instance, one study showed that urban streets with full tree canopies had more pedestrians. Trees pull people outdoors and subliminally encourage neighborhood interaction, which in turn lessens the local crime rate.


“Size does matter,” said Mark. “The bigger the tree, the more the leaves and the more benefits we get out of it.” Removing just one large tree has a serious effect on your neighbors’ health and on the adjacent property values. “What you do impacts everyone,” Mark explained. “Through street trees, in-fill urban parks, and trees on your own property, you must have interaction with nature everyday” Mark noted.


One of the best sessions of the day was “Green Infrastructure Planning.” Speaker CJ Lammers, a supervisor in the Environmental Planning Section of MNCPPC, said it is imperative that we “plan to ensure nature does not go someplace else.” Her wise advice to citizen activists was to not waste your energy and efforts fighting to stop development. It is coming no matter what as we are a growing county and our population will only be increasing. You won’t win that battle.


Instead, she advised us to fight to shape the development. “Be sure to talk to the planners early in the process,” encouraged CJ. She gave a great example of a community inside the beltway in Prince George‘s County that her department worked with the nearby residents and developer to build compromise and save two important river watershed areas on the property.


Alice Ewen Walker, executive director of the Alliance for Community Trees (ACT), discussed ways to get grass-roots community involvement by local volunteers in tree planting and maintenance programs. She believe in getting folks involved and giving the real responsibility for their neighborhood trees, not just token one-day tasks.


Paul Meyer from the Morris Arboretum discussed new and underutilized tree species for stressful sites such as those found in many urban settings. His recommendations were for under-utilized trees that can take the urban heat, pollution, and foot traffic. Among his top choices are: Oriental and American planetree, Lacebark pine, Eastern red cedar, Japanese camellia, Northern bayberry, and Ginkgo biloba. I hope you will consider planting one or more of these trees and looking at a lower AC bill next summer.


(I took the photo above during the June heat wave on a particularly grueling expanse of bare sidewak along Waybe Avenue near downtown Silver Spring, MD.)


About the author:

Kathy Jentz is editor of Washington Gardener magazine and is a long-time DC area gardening enthusiast. She has just planted two new trees in her small, urban yard. Washington Gardener is all about gardening where you live. She can be reached at www.washingtongardener.com and welcomes your gardening questions.


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About the Author

Kathy Jentz
Kathy Jentz is editor of Washington Gardener magazine and is a long-time DC area gardening enthusiast. Washington Gardener is all about gardening where you live. She can be reached at @WDCgardener on Twitter and welcomes your local DMV gardening questions.

2 Comments on "Urban Trees = Nature’s AC"

  1. Steve Davies | July 16, 2010 at 12:44 pm |

    Hi Kathy
    Thanks for the information. I’d be interested in your take on the current solar panels vs. tree debate in Takoma recently written up in the Gazette.
    By the way, I was checking out the Casey Trees site and saw that they say the AC benefits are $2.6 million per year, not $26 million. Not sure whether they made a mistake on their site or not, but I thought you should know. I will email them and see what the correct figure is
    Cooling Shade
    Cities typically average 10 degrees hotter than suburban areas. Trees provide shade and give off water vapor to cool the city in the summer. Homes shaded by trees have 10-30% savings in air conditioning costs compared to homes without shade. The shade trees of DC save us more than $2.6 million in air conditioning costs per year.

  2. Hi Steve –
    Thanks for stopping by the blog.
    Yes, if you hear definite # from Casey, please let me know. My source from them was a press release and an in-person presentation.
    As to the Gazette piece on solar power vs tree coverage in Takoma Park. It is a tough issue. On the on-hand, you are shooting yourself in the foot by removing tree coverage of your roof and increasing your energy cooling needs. On the other, solar can save trees by eliminating the need for fossil fuel sources.
    In an ideal world, you would orient your house and your plantings plus solar panel installations to best take advantage of the sun’s power and tree assets.
    IMHO, if PEPCO is cutting down (with seeming impunity) trees for overheard electrical wire access in our communities what is the difference if a homeowner wants to do it themselves for an alternative energy source? You can’t allow one and not the other.
    In the specific case in the Gazette story, the tree is dead and rotting so I side with the pro-solar power owner with the caveat that he plant at least 3 trees (that will have eventual sizes of some caliber) to replace the tree loss and sight them well for future energy savings.

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