SAN ANTONIO, Texas, November 12, 2002 (ENS) - Tree cover around San Antonio is saving the city about $70 million a year in ecological services, shows a study released today by conservation group American Forests. American Forests conducted an Urban Ecosystem Analysis (UEA) of 788,000 acres of the greater San Antonio area to show changes in tree cover over time. The study revealed the value of the area's tree cover for storm water management, air quality and energy conservation.
The study not only calculated the functional value of trees but also serves as an introduction for the city leaders to learn about ways to use tree cover as an asset, building a green infrastructure for future city management decisions. American Forests will work with the community over the next year to help integrate trees into planning and management operations.
"Based on this study, City Public Service (CPS) will develop a comprehensive tree planting and preservation program called 'Planting Our Future,' which will help improve air quality in San Antonio and save CPS customers on air conditioning costs," said Milton Lee, CPS general manager and CEO.
The UEA technique conducted in San Antonio used satellite and aerial imagery, geographic information system technology, and scientific research to calculate the benefits trees provide to the urban environment. American Forests' CITYgreen(r) computer software was used to analyze the environmental benefits of the greater San Antonio area.
The findings show that in the greater San Antonio area, the existing tree cover reduces storm water runoff by 678 million cubic feet during a storm event. Storm water construction costs to contain this same amount of storm water would be valued at about $1.35 billion.
Besides reducing storm water runoff, the tree canopy provides also removes 17 million pounds of pollutants a year, a value estimated at $42.1 million a year. The city's urban forest stores an estimated seven million tons of carbon and sequesters almost 56,000 additional tons of carbon each year.
Trees also help shade and cool the greater San Antonio area. Long, hot summers force residents to use their air conditioners at an approximate cost of $555 dollars per home each year. Residential shade trees were shown to save each home an average of $76 a year.
Assuming that 67.8 percent of the area's residences have air conditioners, based on U.S. Census Bureau figures, the estimated annual residential energy savings totals $17.7 million.
These benefits become more important with the realization that tree canopy has been lost over the last 15 years. The analysis compared classified Landsat(tm) satellite images between 1985 and 2001 and revealed a 23 percent loss in heavy tree canopy cover - 50 percent or greater tree cover - over this time period.
"The study shows that San Antonio's trees are a vital municipal asset," said Gary Moll, vice president of American Forests' urban forest center. "In the next phase of the study, we will use high resolution, multi-spectral imagery to exam these numbers more closely and analyze them by different land cover and land use categories.":
