Much of this information
was provided by:
www.americanforests.org/
Trees Reduce Stormwater Runoff
Metropolitan areas with adequate tree cover are much better places to live and having more trees in the yard and along the streets pays big dividends. Trees in urban areas function like the public utilities reducing stormwater runoffs, improving air quality, and reducing energy consumption.
Trees reduce stormwater and save us money. As communities grow, trees are removed to make way for impervious surfaces such as parking lots, roads and buildings. Our studies show that impervious surfaces have increased by 20% over the past 2 decades in urban areas. Constructed stormwater facilities are created to compensate for the tree loss. These facilities are expensive to build and maintain. The cost has been calculated to be in excess of $100 billion nationally.
So, what can we do? Design with nature. Increase the tree cover and reverse the national tree deficit. It is a philosophy that pays rather than costs.
More information can be found at this site:
http://www.forester.net/sw_0203_trees.html
or in this study:
http://www.americanforests.org/download.php?file=/graytogreen/treeshelpcities.pdf
or in this American Forest instruction manual:
http://www.americanforests.org/download.php?file=/graytogreen/stormwater.pdf
Trees Reduce Air Pollution
Air pollution in our cities, and even our suburbs, is a serious concern as we enter the twenty first century. The burning of fossil fuels has introduced a steady flow of deadly pollutants into our atmosphere, yet very few urban areas can meet national clean air standards. Luckily, we are surrounded by efficient air cleaning machines—trees. Trees sequester many pollutants from the atmosphere, including nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), carbon monoxide (CO), and particulate matter of ten microns or less (PM10).
Dave Nowak, Ph.D., of the USDA Forest Service conducted research in 50 US cities and developed a methodology to assess the air pollution removal capacity of urban forests with respect to the above pollutants. American Forests uses this research to determine the work trees do to clean the air with CITYgreen software—a desktop GIS program that calculates the value of trees to urban environments. The program estimates the amount of pollution being deposited within a given study site based on pollution data from the nearest city then estimates the removal rate based on the area of tree and/or forest canopy coverage on the site.
Air Quality benefits are reported both in lbs removed per year, as well as annual dollar savings. Dollar values for pollutants are based on the median value of the externality costs set by the Public Service Commission in each state.
Additional information can be found in this Citygreen Report: http://www.americanforests.org/download.php?file=/graytogreen/airpollution.pdf
Trees Reduce Energy Consumption
Anyone who has ever sat under a tree on a hot summer day has appreciated the cooling ability of trees, but trees can do more than just provide shade for a picnic. Trees cool our neighborhoods in the summer and save us money on energy costs and related water usage and air pollution. American Forests has developed a method for estimating the energy conservation benefits of trees from direct shading of one and two-story residential buildings. This method is the result of research conducted by Dr. Greg McPherson of the USDA Forest Service.
Trees are most effective when located to shade air conditioners, windows, or walls and when located on the side of the home receiving the most solar exposure. In many parts of the country the west side is most valuable, followed by the east and south, although this ranking can change based on geographical considerations.
Research by the USDA Forest Service and others has shown that trees strategically planted to shade homes can reduce air conditioning bills significantly. As a result, local power plants are not required to produce as much electricity, and thus emit less pollution, including carbon. In urban and suburban areas, the amount of this avoided carbon output outweighs even the amount of carbon sequestered by the natural forest as it grows.