You know that trees are an indispensable factor in our environment. You know that they supply the oxygen we breathe and make our surroundings more beautiful. But, there are some incredible benefits of trees—especially in an urban setting— that you may have never considered.
How do urban forests benefit our cities? Let us count the ways…
The United States’ urban forests remove an estimated 800,000 tons of air pollution from the Earth’s atmosphere every year. With all the buildings and vehicles pumping out harmful greenhouse gases, the trees’ ability to purify the air has become more necessary than ever.
The U.S. Forest Service has reported that a tree’s “net annual oxygen production” varies by the species, size, health and location of the tree. For example, a healthy 32-foot-tall ash will produce about 260 pounds of oxygen annually. Given that a typical human being will consume 386 pounds of oxygen each year, it would take two medium-sized, healthy trees to supply the amount oxygen needed for one person over that amount of time. And, according to the USDA Forest Service, there are 610 million trees in U.S. urban areas working for the country’s population of roughly 314 million.
Because cities have so many impermeable surfaces (concrete, asphalt, etc.), rainwater pools instead of being absorbed into the ground. This makes it possible for even a small rainstorm to cause flooding. As built-up rainwater flows over the pavement, it becomes polluted and will likely end up in our urban waterways — or even our faucets.
One street tree is capable of intercepting 760 gallons of rainwater in its crown, which helps to reduce runoff and flooding. Collectively, enough urban trees can result in a city not having to build as many artificial stormwater controls, which will save the city and its citizens millions of dollars. The rainwater that falls on an urban forest is also purified before it reaches the ground, and any that is retained helps to sustain the growth of the trees, parks and vegetation.
Reducing Energy Consumption
Urban forests provide shade for our homes, businesses, roads and parking lots. Strategically planted trees around a home can provide enough shade to drastically reduce air-conditioning use in the summer. And, their ability to cut wind exposure can also reduce heating bills in the winter.
Urban trees can also reduce the noise of a city significantly. Tall trees with dense crowns and a soft ground surface can cut noise by 50 percent or more (link). If kept healthy and cared for properly, urban trees can also provide bird and wildlife habitat and recreational opportunities, improve soil quality, reduce erosion, add to property values.
Many studies suggest that urban trees help to provide a feeling of community well-being. Several such studies have proven that street trees contribute to fewer property crimes and a better economy. Experts report that tree-lined streets attract tourists and consumers, encouraging them to shop and dine a little longer. This research also says that real estate in wooded areas is bought and rented more quickly.
Climate Change Mitigation
Urban Forests help to stave off climate change in two ways: through the absorption and sequestration of carbons, and by reducing the amount of greenhouse gases that are emitted.
Trees and shrubs can store carbon in their heartwood, roots and leaves for decades — even centuries — removing carbon dioxide from our atmosphere and and slowing the rate of climate change. In fact, urban trees in the U.S. store 770 million tons of carbon.
Because trees help limit the need for cooling and heating, they effectively reduce the amount of greenhouse gases emitted by power plants, commercial and residential buildings. According to the U.S. Forest Service, “reduced emissions from trees can be substantial, especially in regions with large numbers of air conditioned buildings, long cooling seasons and where coal is the primary fuel for electric power generation.”
So, the next time you find yourself amongst an urban forest, do as the Japanese do, and soak it up.
Sara Thompson has published numerous articles about tree care, environmental issues, and green building. This article was written in collaboration with the certified arborists at Inexpensive Tree Care in Portland, Oregon.