May 8, 2013
Urban Trees Don’t Just Beautify, They Provide An Economic Boon Too
Brett Smith for redOrbit.com - Your Universe Online
Whether it´s Manhattan´s Central Park or the Emerald Necklace in Boston, Frederick Law Olmstead understood the value that forested areas bring to a city. However, the“¯father of American“¯landscape architecture was probably unaware of the billions of dollars these forests contribute in the form of carbon storage and sequestration.
According to a new study in the journal Environmental Pollution, urban trees store a total of over 700 million tons of carbon at an estimated value of $50 billion. The trees also take in an additional 21 million tons of new carbon each year at a value of about $1.5 billion.
“With expanding urbanization, city trees and forests are becoming increasingly important to sustain the health and well-being of our environment and our communities,” said Tom Tidwell, a service chief with the US Department of Agriculture´s Forest Service who was not directly involved in the research.
“Carbon storage is just one of the many benefits provided by the hardest working trees in America,” he added. “I hope this study will encourage people to look at their neighborhood trees a little differently, and start thinking about ways they can help care for their own urban forests.”
To determine the carbon-based value of the trees, researchers from the Forest Service needed to determine how much carbon urban trees could store. Using tree field data from 28 cities and six states along with national tree cover data, the team was able to estimate total carbon storage in the nation's cities.
The researchers found that the states with the greatest amount of carbon storage in urban areas are Texas, with 49.8 million tons, and Florida, with 47.3 million tons.
The study could become more significant as the as urban areas expand, since cities in the contiguous US have increased from 2.5 percent of land area in 1990 to 3.1 percent in 2000. If that growth trend continues, urban land area could grow to the size of Montana by 2050, the Forest Service said in a statement.
However, the researchers noted that the growth of cities doesn´t necessarily translate into more urban forests. In 2012, Nowak and study co-author Eric Greenfield, found that urban tree cover is in decline across the US at a rate of about 4 million trees annually.
While the study is not the first to investigate carbon storage by US urban forests, it does provide a more detailed statistical analysis for national carbon estimates. The researchers also recommended that urban planners and property owners maintain space for trees and plant new trees each year.
“Planting trees in energy-conserving locations around buildings can reduce building energy use and consequently emissions from power plants,” they wrote. In addition, “(t)ranspirational cooling and changes in (sunlight reflection) due to trees alters urban microclimates that can also reduce carbon emissions from cities.”
The research also suggested that future studies should take a more holistic approach and investigate the urban soils where these trees live.
“More research is needed on the cumulative effects of trees, soils and their management in urban areas though carbon estimates for urban ecosystems are improving through time as new data become available,” the authors wrote.