URBAN FORESTS / TREES

McAliney, Mike (ed.) Arguments for Land Conservation: Documentation and Information Sources for Land Resources Protection, Trust for Public Land, Sacramento, California, December 1993.

"The American Forestry Association estimates that the average economic contribution of a single tree is $73 in energy conservation, $75 for erosion control, $75 for wildlife shelter, and $50 for air pollution benefits. Over its lifetime, an average tree provides more than $57,000 in environmental and economic benefits."

"Other studies show that the carbon dioxide emitted into the atmosphere by burning fossil fuels (cars and power plants are the worst offenders) are absorbed by a single mature tree at the rate of 48 pounds a year. This same tree releases enough oxygen to support two human beings."

Comstock's, "Nature's Dustmop," June, 1993.

Research has demonstrated that 100 million mature trees in U.S. cities (one and a half trees for every single family home) could reduce energy use by 30 billion kilowatt hours, saving approximately $2 billion in annual energy costs which is more than the annual gross receipts from all sales of trees from our National Forests. Associated with this savings is a projected reduction of nine million tons per year of carbon dioxide emissions from power plants.

H. Akabari, "The Impact of Summer Heat Islands on Cooling Energy Consumption and CO2 Emissions," American Council for an Energy Efficient Economy, 1988

Studies made in cooperation with electric utility companies show that when the costs of planting, watering and maintaining trees are considered, tree planting is a more cost-effective energy conservation and carbon dioxide reduction strategy than many other conservation measures.

E. G. McPherson, "Cooling Heat Islands with Sustainable Landscapes," In Proceedings of the Sustainable Cities Symposium, Chicago, 1991.

Trees play a critical role in reducing air pollution in urban environments. A Chicago study found that 120 acres of canopy cover can absorb up to 5.5 pounds of carbon monoxide, 127 ponds of sulfur dioxide, 24 pounds of nitrogen dioxide, and 170 pounds of particulates per day. Trees in a 525 acre area of Lincoln Park had an annual air pollution mitigation value equivalent to around $25,000 of traditional air pollution controls.

David J. Nowak and E. Gregory McPherson, United States Forests Service Northeastern Forest Experiment Station, 1993.

Texas Parks and Wildlife. July 1994. "City Parks: Human Investment, Natural Reward."

"With increasing population, preserving a city's natural environment becomes crucial if it is to remain habitable and sustainable. 'A single tree in a city is 15 times more capable of reducing carbon in the atmosphere than a tree in the forest,' said Eric Beckers of the Texas Forest Service. 'Trees create a much more livable environment. They provide shade that reduces electricity costs, increases property values, attracts wildlife, produces oxygen and sequesters carbon, reduces stormwater runoff and creates a more comfortable and aesthetically pleasing environment.'"

Fox, Tom. 1990. Urban Open Space: An Investment that Pays. The Neighborhood Open Space Coalition, New York, New York.

"A 1976 study that evaluated the effects of several different variables on homes in Manchester, Connecticut, found that street trees added about $2,686, or 6%, to the sale price of a house."

A 1989 study of properties in Cambridge, Massachusetts showed that street quality ratings, judged by characteristics such as the width of the street, volume of traffic, ease of parking, the presence of healthy trees and landscaping, accounted for up to 30% of a house's market value. "In 1987, the average price for a single-family home was $235,000. A regression model showed that depending on street quality, otherwise identical properties had about a $70,000 difference in price. When Cambridge tax assessors judge streets from 'excellent' to 'poor', street trees rank as their number-one priority in a rating a street 'excellent'."

William Schmergel, president of Schmergel Construction in Great Neck, New York, was building 56 town houses on a 12-acre site. 'Premium lots sell first,' he said in the article, 'and trees sell the job.' His two- and three-bedroom houses had prices ranging from $215,000 to $315,000 and the highest premium--$25,000-- was placed on units that overlooked a 35-foot wide buffer of woods, ensuring privacy and appealing views.

Brabrec, Elizabeth. 1992. "Trees Make Sense." Scenic America: Technical Information Series v. 1 (1).

"Trees are an important part of the local and national fight against air pollution and against the progress of global warming. By removing carbon dioxide and other pollutants from the air and releasing oxygen back into the air, trees improve air quality. Air pollution levels are measured by the amount of particulate matter in the air, high levels of which are irritating to the respiratory system. Trees aid in removing particulate matter from the air by trapping particles on the exposed surfaces of twigs and leaves."

A look at air pollution along freeways found that "greenbelts could contribute significantly to air quality. The study found that air pollution along freeways is approximately three times higher than that acceptable to man. A green belt one-half mile wide on either side of a highway could readjust this air balance by removing significant pollutants from the air."

Nelson, William R., Jr. 1975. "Trees in the landscape: A Look Beyond the Obvious", Journal of Arboriculture 1:121-128.

"Trees function in the sound reduction process by modifying humidity and climate, by absorbing sound and by deflection and refraction.In a study of the economic impacts of expressway noise pollution, Roger Vaughan and Larry Huckins (1975) looked at the decline in property values that could be attributed to the level of noise in a neighborhood in Chicago. The estimates ranged from a high of $18 million to a low of $8 million in 1975."

McCaul, John. 1990. "Living in Los Angeles County- The Role of Recreational Opportunities in Assuring the 'Quality of Life' and Long-term Economic Health of the County".

One of the recommendations by the South Coast Air Quality Management District (SCAQMD) for improving Los Angeles' air quality:

"planting trees and expanding parklands in will improve the air quality of LA county. A total of 300 trees 'can counter balance the amount of pollution one person produces in a lifetime.' Proposition B provides for a $10 million competitive grant program for tree planting throughout the County, and any purchases of additional parkland will help preserve remaining open space and natural areas."

Poole, William. 1993. "The Case for Urban Open Space." Draft report prepared for Trust for Public Land, San Francisco, California.

"Human activity place a stress on urban environments that green spaces help relieve. Trees and other vegetation absorb ozone, carbon dioxide, sulfur dioxide, nitrogen dioxide and other noxious air pollutants. Trees remove dust and particles from the air, including dangerous heavy metals. During a one growing season, a single sugar maple 12-nches in diameter was found to have removed 60 milligrams and 140 milligrams respectively of the heavy metals cadmium and lead. The transpiration of water by plants helps control and regulate humidity and temperature. A single tree can remove as much heat from the air as five average-sized air conditioners. Trees and vegetation also break the wind, moderating temperature in winter. The result is a decrease in energy consumption, along with its costs and associated pollution. Parks in stream valleys or urban wetlands absorb storm water much more cheaply than in artificial systems. Large open spaces also allow rain water to be absorbed slowly and to percolate into underground aquifers--reducing the danger of flash flooding or erosion due to rapid runoff."

( Michael Hough, City Form and Natural Processes, New York: Von Nostrand Rinehold, 1984. pp39-46.)

Dwyer, John F. 1993. "The Economic Contribution of Trees to Urban Communities." In Trends: Justifying Recreation and Parks to Decision Makers. v. 30, no. 4.

"Trees have been found to be effective for conserving energy used for residential heating and cooling. Windbreaks have been found to reduce residential heating costs by 10-15 percent, while shade and evapotranspirational cooling from trees have been found to reduce cooling costs by 20-50 percent. The maximum potential annual savings from energy-conserving landscapes around a typical residence ranged from 13 percent in Madison up to 38 percent in Miami. Projections suggest that 100 million additional mature trees in U.S. cities (three trees for every other unshaded single-family home) could save over $2 billion in energy costs per year."

"Analysis of the willingness of users to pay for urban parks and forest preserves indicates that they are willing, on the average, to pay $1.60 more per visit to have a site that was 'mostly wooded, some grassy areas under trees,' rather than 'mowed grass, very few trees anywhere.' Based on nine visits per year to local parks for every person in the United States and $1.00 per visit attributed to the presence of well-managed urban forest resources (both conservative estimates based on studies in the Midwest), the potential contribution of trees and forests in urban park and recreation areas to the value of recreation experiences provided across the nation could exceed $2 billion."

"Trees reduce air pollution through absorption of gases and interception of particulates. They also reduce temperatures which reduce emissions from a number of sources. To the extent that trees improve air quality, there is potential for even greater savings through reduced health care, less material damage and cleanup and improved visibility."

"Trees intercept rainfall and reduce runoff, thereby functioning like retention / detention basins that are essential to many communities. Reduced runoff due to rainfall interception can also reduce stormwater treatment costs in many communities, reduce flooding, and improve water quality."

Page last updated 04/03/2000