How the Smithsonian Gardens Tree Collection Benefits the Environment and Our Well-Being
The Smithsonian Gardens Tree Collection currently consists of over 1,900 trees spread across the Smithsonian’s downtown Washington, D.C. campus as well as at the Institution’s support facilities in Maryland. These trees add great aesthetic value to the grounds, and complement the flowers, shrubs, and other plantings in the gardens here. However, and perhaps more importantly, these trees offer a myriad of environmental and health benefits.
During the summer of 2015, information on all of the collection trees was run through i-Tree, a software program developed by the U.S. Forest Service to calculate the benefits of trees. The results were eye-opening, and it was encouraging to see how much our trees benefit our campus, city, and planet.
Poor air quality, especially in urban areas, can lead to decreased human health, poor visibility, and damage to plants. Trees in urban forests help improve air quality by capturing air pollutants, reducing air temperatures, and decreasing energy consumption in buildings which reduces overall air pollutant amounts by lowering demand on power plants. The SG Tree Collection was calculated to remove 2,700 pounds of air pollutants (carbon monoxide, ozone, nitrogen dioxide, sulfur dioxide, and particulate matter) annually with an associated monetary value of $31,185. This is the equivalent of taking ten cars off the road for a year!
One of the most important environmental challenges we currently face is global climate change. Trees can help mitigate this problem by capturing atmospheric carbon and storing, or sequestering, it for many years. As trees grow, they continually store carbon in the new wood they produce. The trees in the SG Tree Collection store an estimated 37,877 pounds of carbon annually. The large majestic oaks, elms, and other trees found at the National Museum of American History sequester twice as much carbon as the trees found in any other Smithsonian garden or landscape.
Surface runoff of stormwater is a cause for concern in urban areas because it can contribute to pollution in streams, rivers, lakes, wetlands, and oceans. Precipitation that reaches the ground and does not infiltrate the soil becomes surface runoff, which carries pollutants into waterways. Urban trees reduce this runoff by intercepting the water in the tree canopy and allowing it to evaporate over time. Additionally, water that lands on trees may run along the branches and down the trunks which helps it reach the ground more slowly and infiltrate the soil. Smithsonian trees intercept 383,705 gallons of rainfall annually, thereby preventing it from becoming surface runoff.
In addition to these environmental benefits, many recent studies show how trees, especially in urban areas, contribute to better health for people. Areas that have many trees can lower blood pressure, have a calming effect on teens and adults with ADHD, improve breathing for those with asthma and other lung conditions, decrease healing times for sickness and injury, contribute to overall emotional and psychological health, and even improve birthweights of newborns!
We appreciate trees for their beauty and grandeur, especially at this time of year when they come ablaze with autumn colors. Beyond appreciating their beauty, it’s important to remember all of the environmental and health benefits they provide as well. Planting and properly maintaining trees are important steps to take to continue to improve the world in which we live. We here at Smithsonian Gardens are proud to do our part in contributing to that goal.
– Greg Huse, Smithsonian Gardens Arborist and Tree Collection Manager