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You may have noticed that Somerville streets seem a little leafier lately. In a densely built urban city like Somerville, greening our streets and neighborhoods can be a difficult task, but it’s a challenge we’re committed to taking on. Part of the solution to that challenge is expanding our tree canopy, which is why last month we planted 575 new public trees throughout Somerville as we march toward our goal of planting 2,000 new trees by the end of 2015. Public trees do more than beautify our neighborhoods, although that’s important too. Increasing our tree canopy improves our air quality, saves energy costs and can even help slow down traffic and deter crime. In short: the healthier our trees, the healthier our community.
We realized this six years ago when we formed the Somerville Urban Forest Initiative, a way to preserve and manage the trees we already have and a plan to expand our tree canopy. It started with a comprehensive public tree inventory, first completed in 2009 and now publicly available online. Once we knew what we already had in the ground, we developed an Urban Forest Management Plan that mapped out where we needed to plant more trees to connect tree canopies, how we should diversify the species of our trees—we planted 12 different species last month—and how to manage what we have now and in the future.
This effort is about our quality of life and the direct, positive impact that trees can have on an urban environment. Urban areas that have a complete tree canopy, according to one study, can reduce the amount of ozone, particulate matter and other air pollutants four times as much as city averages, according to a USDA Forest Service study. That same study said that in 1994, trees in New York City removed an estimated 1,821 metric tons of air pollution from the air New Yorkers breathe.
We all know about escaping the city during the summer to beat the heat. Pavement and concrete radiate and retain heat. The U.S. Environmental Protection Agency says that annual mean air temperature of a city with 1 million people or more can be roughly 2 to 5.4 degrees hotter than the nearby suburbs and rural areas during the day and as much as 22 degrees hotter at night. Combating this “heat island” effect by increasing our tree cover is an action we laid out in SomerVision. It improves our air quality because many pollutants and ozone-forming chemicals are temperature dependent, and also reduces the risk of heat-related illnesses. A more expansive tree canopy also reduces energy costs by shading our streets and buildings in the summer and blocking winds in the winter, making it less expensive to cool or heat our homes and offices.
Trees contributing to a healthier environment are perhaps an obvious conclusion, but greener city streets with a connected tree canopy may also make our city safer as well. Studies show that street trees may actually cause drivers to slow down and subsequently reduce both the severity and frequency of accidents. And studies done in Baltimore and Portland, Oregon, suggest that connected, tall tree canopies are associated with a decrease in crime.
All these studies point to the measurable benefits of increasing the number of trees we have in the city, but there’s something to be said for the simple fact that it’s pleasant to look out your window and see a tree shading your street. Of course, in Somerville we measure that, too. In the most recent Happiness Survey completed by our SomerStat Office in December, the results suggested that aesthetics and physical beauty are one of the top predictors of whether residents are satisfied with their neighborhood, and subsequently the city as a whole.
With the new trees planted last month, we’ve now planted more than 1,000 trees since 2011. There’s still the challenge of finding the right spot to plant trees in an already dense urban environment. We have to make sure our sidewalks remain accessible to all people of all abilities, and that trees don’t block those sidewalks or cause buckling or cracking sidewalks. So we’ll continue to use a smart, strategic process to build out our tree canopy. The City can use your help, too, in caring for our public trees by following some simple guidelines. And together, we can realize all the benefits of a true urban forest.