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Kaid Benfield’s Blog

What trees mean to communities: more than you may think

Kaid Benfield

Posted July 31, 2012

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  street trees in Winnipeg (by: Leah100, creative commons)

I am lucky enough to live in a neighborhood with many large, mature trees.  Our bit of urban forest is one of our community’s greatest assets, if you ask me.  But, loved though they are, trees are getting to be a little controversial in and around DC, and that worries me.  I’ll get to that a bit later in the post, but first I want to share some of things I have learned about city trees in the last few days.

In particular, last week I spoke at a forum hosted by the California Center for Sustainable Energy, and after the program I was approached by someone from an initiative called San Diego County Trees.  The initiative is the urban forestry project of the Energy Center, and they have all sorts of information extolling the benefits of urban trees along with a crowdsourced inventory of street trees in San Diego. 

  San Diego Tree Map (by: San Diego County Trees)

I just spent time on the website, where the coolest feature is an interactive map of the whole county showing very specific tree locations and information, including quantified benefits to the region stemming (pun unintended but acknowledged) from its trees.  As you can see in the image, these include carbon sequestration, water retention, energy saved, and air pollutants reduced.

You can even click on a specific tree and get detailed information on its species, size, and annual economic benefit to the community.  San Diego County Trees invites its readers to add to the inventory with information on additional trees not presently counted.

  detail, San Diego Tree Map (by: San Diego County Trees)

If you’re interested in the subject of the community benefits of trees, you can get additional information from the websites of the National Arbor Day Foundation and the US Forest Service.  Among the tidbits I learned on one or the other of those two sites are these:

  • The net cooling effect of a young, healthy tree is equivalent to ten room-size air conditioners operating 20 hours a day.
  • If you plant a tree today on the west side of your home, in 5 years your energy bills should be 3 percent less. In 15 years the savings will be nearly 12 percent.
  • One acre of forest absorbs six tons of carbon dioxide and puts out four tons of oxygen. 
  • A number of studies have shown that real estate agents and home buyers assign between 10 and 23 percent of the value of a residence to the trees on the property.
  • Surgery patients who could see a grove of deciduous trees recuperated faster and required less pain-killing medicine than matched patients who viewed only brick walls.
  • In one study, stands of trees reduced particulates by 9 to 13 percent, and the amount of dust reaching the ground was 27 to 42 percent less under a stand of trees than in an open area.

  Bethesda, MD (c2012 FK Benfield)

Several years ago, walkability guru Dan Burden wrote a detailed monograph titled 22 Benefits of Urban Street Trees.  Among other things, he calculated that “for a planting cost of $250-600 (includes first 3 years of maintenance) a single street tree returns over $90,000 of direct benefits (not including aesthetic, social and natural) in the lifetime of the tree.”  Burden cites data finding that street trees create slower and more appropriate urban traffic speeds, increase customer traffic to businesses, and obviate increments of costly drainage infrastructure.  In at least one recent study (reported after Burden’s analysis), trees were even found to be associated with reduced crime.

I think some of the most important benefits, though, are felt emotionally.  Burden puts it this way:

“Urban street trees provide a canopy, root structure and setting for important insect and bacterial life below the surface; at grade for pets and romantic people to pause for what pets and romantic people pause for; Washington, DC (c2012 FK Benfield)they act as essential lofty environments for song birds, seeds, nuts, squirrels and other urban life. Indeed, street trees so well establish natural and comfortable urban life it is unlikely we will ever see any advertisement for any marketed urban product, including cars, to be featured without street trees making the ultimate dominant, bold visual statement about place.”

That is extremely well said. 

The DC area also has an extensive tree inventory hosted by the nonprofit Casey Trees, which has done much praiseworthy work to increase both plantings and awareness in our area.  Among the several informative maps on the organization’s website is one marking trees recently planted in the city directly by the foundation.  There’s also a map showing trees recently planted by the city.  As with the San Diego maps, you can zoom in and click on a particular tree and bring up a popup window (see below) of tree characteristics.

Casey also publishes an annual Tree Report Card evaluating how the area is doing with respect to such performance measures as tree coverage, health, planting and protection.  For 2011, for example, the organization found that tree planting has been robust and that the health of the city’s forest is strong.  But the organization expressed concern about weak enforcement of the city’s tree protection law and urged both legislative and administrative changes to strengthen the city’s aggregate tree canopy, which has remained constant for several years at 35 percent coverage of the city, short of the goal of 40 percent.

  DC tree map (by: Casey Trees)

Which brings me to the controversy.  The Washington region, like many others in the US, has many neighborhoods (including my own) with above-ground utility lines strung overhead along our streets.  We also have a lot of thunderstorms, which in some years cause significant treefall and power interruptions, most recently for the better part of a week during a severe heat wave.  Utility workers strive heroically to restore service, but there are not-entirely-unfounded complaints that some of the local utilities lack sufficient preparation and have cut budgets in the wrong divisions of the company.  This became a major news story, as some electricity providers performed significantly better than others in restoring electricity.

To try to shorten what could become a long story, some defensive utility executives have pointed to the trees when customers complain (“At the hearing, Pepco officials blamed trees for much of the damage to about 2,400 Pepco power lines, 200 transformers and 240 utility poles that fell during the storm”).  This has been refuted by analysis, however (“By far, Pepco equipment failures, not trees, caused the most sustained power interruptions last year, records show”). 

But it’s not just utilities, unfortunately.  As reported by Justin Jouvenal in The Washington Post, a “massive and iconic oak that stood in the heart” of a northern Virginia suburb fell two weeks ago and crushed a car and driver underneath, killing the driver.  This has prompted at least one local businessman to ask the authorities to immediately take down two nearby large, mature trees and to “deal more aggressively with aging trees” in the community.  Some community members are now claiming that tree lovers “have blood on their hands,” while others believe that some of the area’s grandest trees could be casualties of an emotional rush to judgment in the wake of a tragic accident.

  autumn in Vancouver (by: Junichi Ishito, creative commons)

Personally, I am unqualified to evaluate risks and benefits in these situations.  But one resident quoted in the article appears to be a voice of reason, asserting that it is important that trees be evaluated but that weight should be given to professional arborists as to their health and safety.  If a tree is healthy and not posing a hazard, it should stay.  I would add that, if some should indeed come down, the affected property should be replanted as soon as possible.  And, as for the power lines, let’s put them underground where they belong.

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Kaid Benfield writes about community, development, and the environment on Switchboard and in other national media.  For more posts, see his blog's home page.  Please also visit NRDC’s Sustainable Communities Video Channels.

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Jane LafleurJul 31 2012 08:45 AM

Nice blog, Kaid. I am a huge fan of trees and in fact, live in a designated "Tree City USA". I totally agree with the resident's position about evaluating trees and determining if they are a hazard or not and replacing with young trees asap. However, hazards are sometimes in the eye of the beholder. Some DOT's find trees FDO's (fixed deadly objects) and see that they are removed anywhere in the right-of -way. Undergrounding utilities is a great option but expensive - $1million per mile I have been told. I think the solution is a tree to tree site walk and evaluation. My organization did this for a Route One reconstruction project, serving as the mediator between DOT and citizens who were concerned about the loss of hundreds of trees. The tree to tree site walk resulted in "saving" dozens of trees that were slated for the chain saw, within the right-of-way, but not dying or hazardous. I opt for the case by case basis whenever possible.

Ken FirestoneJul 31 2012 11:21 AM

Trees should be appropriate for where they are planted. A tall tree, such as an oak, should not be planted under overhead utility lines. And it is probably not a good idea to plant a tall tree that is easily uprooted near a house or other building.

Dan Staley Jul 31 2012 11:52 AM

This is very common. People take trees for granted until they fall on your house in a storm, then the caterwauling starts. It will die down soon enough.

Most trees that we use in our cities are not used to being open-grown. Put them in a lawn, compact the soil and water shallowly, and the tree is stressed.

It is surprising that more trees don't fall on things in our cities, with the shameful way we care for our trees.

Robin RivetJul 31 2012 03:02 PM

At San Diego's California Center for Sustainable Energy last week, Kaid presented the most sensible view I've heard in along time about what makes for sustainable communities. I'm so glad to see the virtues of urban forestry being lauded in this forum. The county of San Diego's tree ecosystem map was a collaboration with Urban Ecos from San Francisco and funded through a state Cal-Fire grant to promote the broad virtues of the urban forest. If anyone desires to utilize this format in their region, it is free for adaptation, and I will be happy to offer guidance about how to proceed.

Alison PockatAug 1 2012 11:38 AM

This brings to mind a fight my Mom has had with the power company for the past 43 years. She has a Slippery Elm that is actually listed as a champion tree and yet the power company has repeatedly attempted to cut it down - prompting a need for continuous vigilance and occasional threats of legal on her part to protect her tree. Ironically the power line in question has never been touched by her tree and in fact the bulk of the power problems that they have experienced there have been caused by squirrel damage. Even then more squirrels have died due to the line than have caused outages.

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