Last week in our Why Trees Matter series we focused on the energy savings benefits of trees. This week we will focus on a crucial ecological benefit—carbon sequestration. Carbon dioxide comprises 82% of greenhouse gases emitted in the US according to a 2012 report by the US Environmental Protection Agency. Trees are able to remove carbon dioxide from the atmosphere and store it (sequestration) in their roots, trunk, leaves, and undisturbed surrounding soil. As trees grow, they increasingly absorb more carbon dioxide from the atmosphere. Because trees store more than they release, forests are referred to as carbon “sinks.” Forests store more carbon compared to other land-based ecosystems. One tree can absorb nearly 48 pounds of carbon dioxide a year and sequester 1 ton of carbon dioxide in 40 years. One acre of grown trees is able to capture the amount of carbon dioxide released when one car drives 26,000 miles (that’s over 6 round trips by car from Arizona to New York).
Trees use carbon dioxide as part of their food cycle. Through photosynthesis, carbon dioxide is converted into sugar, cellulose, and other carbohydrates needed to feed the tree. The rate at which a tree is able to store carbon depends largely on the tree type, age, and size. Younger, larger, and faster growing trees, on average, absorb more carbon. Nearly half of the dried wood weight of a grown tree is carbon. Forests are great resources for carbon sequestration and a natural way to slow and even reverse the trapping of heat in the Earth’s atmosphere. As we debate the best ways to favorably alter climate change, perhaps, one of the best ways is to plant trees. The greatest potential for adding the type of forest cover, and its benefits, afforded by trees is in urban areas. Urban forestry can play a large role in reducing greenhouse gases by reducing the energy used for air conditioning, particularly, in places like Arizona. Electricity such as that used for air conditioners accounts for over 30% of carbon dioxide emission in the US. Planting more trees in urban areas not only reduces electricity usage by providing shade and other energy saving benefits, but trees also help sequester the carbon released from urban activities.
Useful tools like this one help predict the amount of carbon dioxide sequestered in urban areas. Punch in your own information about the types of trees you have in your area and see the estimated benefits. Below is an example of the annual benefits (in monetary value) of a mature Mesquite tree planted in downtown Phoenix.
Notice the other estimated benefits afforded by trees such as improving air quality, stormwater runoff prevention, and enhancing property value. Next week we will go into one of these additional benefits that further explains why trees matter.
http://www.epa.gov/climatechange/ghgemissions/gases.html (pie graph #1)
http://www.epa.gov/climatechange/ghgemissions/sources.html (pie graph #2)
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