Monday, May 13, 2013

Green to grey

According to a recent state-by-state US Forest Service study, urban forests are responsible for storing 708 million tons of carbon. As an environmental service necessary to clean air and stabilize climate, this carbon sequestration has an estimated value of $50 billion. Each year, our leafy friends capture an additional 21 million tons of carbon to the tune of a $1.5 billion benefit. Led by Dave Nowak, the research was published in the journal, Environmental Pollution.

The team took field data from 28 cities, six states, and national tree coverage information to calculate the carbon storage in urban areas of the United States. In a previous study done in 2008, total carbon storage from forest land was determined to be 22.3 billion tons. Adding city trees, the number increased to 22.7 billion tons. Rates of sequestration vary across the states depending on the amount of tree cover and growth rate.
The amount of carbon stored in urban trees is expected to increase as cities expand. Urban areas grew from 2.5% of land in 1990 to 3.1% in 2000. However, more development does not always directly translate into more trees being planted. It has already been shown that tree cover helps bring down temperature. As we cut the trees, the heat builds up, requiring more air-conditioners which in turn spew hot air outside, which in turn breeds high humidity, and so on and on. It all begins with a tree that falls down!

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