Trees can have far-reaching effects on community air and water quality, residential heating and cooling, property values, community aesthetics, and even public health. Careful choice and placement of trees helps shade buildings, cool urban heat islands, and minimize conflicts with utilities and other infrastructure. Trees also reduce atmospheric carbon dioxide, remove air pollutants, reduce flooding and water pollutants, help raise property values, and contribute to increased retail sales. They can help calm traffic and reduce noise and the incidence of crime. Finally, trees are one of the few elements of urban infrastructure that actually appreciate in value over time.
Trees Make Places
Trees are one of the defining elements of attractive, inviting and memorable places.
Trees are a hallmark of great streets. They provide a sense of enclosure and of an “outdoor living room” in which the relationship between trees, parkways, sidewalks, yards and homes is human-scaled yet accommodative of cars. Motorists will tend to maintain safe speeds on streetscapes designed in this way.
Shaded pavement makes for cooler neighborhoods, encourages more people to walk, and promotes increased social and recreational outdoor activity. Trees help reduce air temperatures, thereby cutting energy costs. Well-shaded streets often require less frequent repaving, resulting in a more affordable roadway system.
Trees absorb up to the first third of most precipitation through their trunk and leaf system. This moisture never hits the ground. Root structures open otherwise impervious paved surfaces, enabling infiltration of further precipitation into the earth; there it is decontaminated and absorbed by plant roots, and it replenishes ground water and aquifer resources. With sufficient tree cover, stormwater runoff and flooding risk is reduced, water is cleaner, and water supplies are replenished.
Urban Forestry Factsheets and Guidelines
A free LGC fact sheet, offered in English and Spanish, can help local officials, their staff and other community leaders understand and communicate the value of urban trees. “Livable Communities and Urban Forests” Factsheet
Developed by the LGC and the Center for Urban Forest Research and Education, we also have tree selection and planting guidelines for the San Joaquin Valley, Southern Coastal California, and the Inland Empire available in our Resources & Publications section.
Research and Examples
Quantified Environmental and Economic Benefits
The USDA Forest Service Center for Urban Forest Research in Davis, California has developed a tree guidebook series covering many of the major climatic regions of the U.S. Each guidebook quantifies the impact of various tree species on each region, including summary tables of energy, air and water quality, stormwater runoff, and property value impacts. In each case, incorporation of cost projections for planting, maintenance, infrastructure repair, administration, etc. shows favorable economic outcomes with increased forestation. Go to the Center website (http://ohecc.ucdavis.edu/OHECC2003/ppt/mcpherson_files/frame.htm) for the tree guides and much more.
Neighborhood Revitalization and Increased Property Values
From 1995 to 2002, the Pennsylvania Horticultural Society partnered with the New Kensington Community Development Corporation to improve the appearance of a Philadelphia neighborhood and help stem population loss, attract new residents, and encourage reinvestment.
Their comprehensive greening program included “stabilizing” vacant lots (clearing debris and installing fencing and trees), creating community gardens, planting trees, renovating parks, and transferring vacant lots to adjacent homeowners for private use. The results included 480 newly planted trees, 145 settled side yards, 217 stabilized lots, and 15 community gardens.
A University of Pennsylvania impact study found significant increases in property values near cleaned lots, streets trees, and parks. A tree planted within 50 feet of a house could increase its value by about 9%. Overall, tree plantings alone accounted for approximately $4 million in increased community property values; lots that had been cleaned and forested increased total property values by $12 million.
For more information (www.pennsylvaniahorticulturalsociety.org)
A University of Illinois study of 98 apartment buildings in Chicago shows that trees can play an important role in reducing urban violence. Buildings with high levels of greenery had 52 percent fewer total crimes, including 48 percent fewer property crimes and 56 percent fewer violent crimes. Buildings with moderate amounts of greenery had 42 percent fewer total crimes, including 40 percent fewer property crimes and 44 percent fewer violent crimes.
The study’s authors explain that greenery exerts a relaxing and refreshing effect, reducing human aggression and bringing people together outdoors — thereby increasing surveillance and discouraging criminals. A green, well-groomed apartment building signifies attention, care and vigilance on the part of owners and residents.
For more information, visit the University of Illinois at Urbana Champaign Human-Environment Research Laboratory web site (www.herl.uiuc.edu).
Trees boost the prosperity of downtowns and neighborhood commercial areas; areas with ample greenery encourage shoppers to linger, to pay more for goods and services, and to shop more frequently than do treeless areas. This can render main street stores a competitive advantage over mall discount stores and big-box retailers. Studies also indicate that landscaping adds to the dollar value and sales appeal of commercial real estate, and boosts office occupancy rates.
Download the fact sheet, Trees in Business Districts: Positive Effects on Consumer Behavior! for more information.
Seattle and Portland have combined innovative street, parking lot and other landscape design strategies with tree plantings to reduce stormwater runoff and preserve water quality. Go to the following web sites for more:
- Portland Sustainable Stormwater Program (www.portlandonline.com/bes/index.cfm?c=34598)
- Seattle – Natural Drainage Program (www.seattle.gov/util/About_SPU/Drainage_&_Sewer_System/Natural_Drainage_Systems/index.asp)
Policy Initiative: Sacramento Tree Foundation Greenprint Program
The Sacramento Tree Foundation is working with the Sacramento Area Council of Governments (SACOG) to double the region’s tree canopy over the next 40 years, so as to maximize the benefits of urban forests for each of its municipalities.
The Greenprint is a call to action and a plan of work for each of the 28 local governments in the six-county SACOG region to adopt tree canopy goals, policies and ordinances, best management practices, and community involvement strategies. Arborists, urban foresters, landscape architects, engineers, and policymakers contributed technical advice to generate best strategies and guiding principles for the final draft Greenprint policy document. To date, four counties and twenty-six SACOG jurisdictions have signed on to the Greenprint.
For more information, vist the Sacramento Tree Foundation’s Greenprint web site (http://www.sactree.com/doc.aspx?30).
- TreeLink (http://actrees.org/welcome-treelink-itreebank-visitors/)
- American Forests (www.americanforests.org)
- Center for Urban Forest Research, Pacific Southwest Research Station, USDA Forest Service (cufr.ucdavis.ed/)
- Urban Forestry South, USDA Forest Service, Southern Region (www.urbanforestrysouth.org)
- USDA Forest Service, Urban and Community Forestry Program (www.fs.fed.us/ucf)
- USDA Forest Service, Northeastern Research Station, Urban Forest Research Unit (www.fs.fed.us/ne/syracuse)
- National Urban and Community Forestry Advisory Council (http://www.fs.fed.us/ucf/nucfac.shtml)
- Local Government Environmental Assistance Network (www.lgean.org/html/hottopics2.cfm?id=20)
- Free software suite from the USDA Forest Service that provides urban and community forestry analysis and benefits assessment (http://www.itreetools.org/)