My team at the U.S. Forest Service Northern Research Station recently completed a study of the District of Columbia’s urban forest using the publicly available, free iTree software suite. Understanding an urban forest's structure, function and value can promote management decisions that will improve human health and environmental quality. Urban trees clean our air, capture stormwater and provide huge energy savings.
These tremendously important forests are composed of a mix of native and exotic tree species. In Washington, about 70% of the trees are from species native to North America, while 1% is native to the state or district. Species exotic to the District of Columbia make up 30 percent of the population. Most exotic tree species have an origin from Asia (21.6 percent of the species). This urban forest removes an estimated 492 tons of air pollution per year with an associated value of $2.30 million, and reduces energy-related costs from residential buildings by $3.45 million annually.
This study gives us a better understanding of the real value trees bring to our nation’s capital. But the benefits don’t stop there – urban trees across the U.S. are working for us every day.
Key findings of our Washington, D.C., study
• Number of trees: 2,584,000
• Tree cover: 28.1%
• Most common species: American beech, Callery pear, Tulip tree
• Percentage of trees less than 6" (15.2 cm) diameter: 62.6%
• Pollution removal: 492 tons/year ($2.30 million/year)
• Carbon storage: 596,000 tons ($12.3 million)
• Carbon sequestration: 19,000 tons/year ($393 thousand/year)
• Building energy savings: $3.45 million / year
• Avoided carbon emissions: $129 thousand / year
• Structural values: $3.99 billion
U.S. Forest Service Chief Tom Tidwell will unveil i-Tree v.4 tomorrow in Fairmount Park, Philadelphia.
For more urban forest studies, click here.