By: Janette K. Monear and Lorin W. Culver, ASLA 

The USDA Forest Service, iTree, and American Forests CITYgreen program have proven that trees play a major role in stormwater management, air quality and energy conservation and that they are definitely part of a community’s infrastructure. Trees are a capital asset for communities, the older they become the greater the return on investment.

Although trees are generally overlooked as an important and integral part of the urban infrastructure, municipalities are now recognizing, through the absence of trees, that cities need trees, people need trees and trees need people. Cities are looking at how to best meet federal and state regulations for air and water quality through the incorporation of trees and many are even considering the value of trees for selling carbon credits.

In an effort to institutionalize trees in the community-planning process, to expand the criteria for U.S. Green Building Councils’ (USGBC) LEED-ND® and LEED-NC® programs and other landscaping and development criteria, and to integrate trees into city policy, the Tree Trust, a Minnesota non profit, and Bonestroo, a full service planning and engineering firm, have created the “City Tree Sustainability Guidelines and Best Practices.” Although the focus for their creation was the Hawthorne Eco

Village project within the City of Minneapolis, it was understood that they could be utilized in communities throughout the country.

These guidelines promote the consideration of city trees as major and vital urban infrastructure. They outline best practices to incorporate them into the urban framework.

A primary goal is to assure that healthy urban trees reach maturity, continue to thrive, and not create future problems or conflicts with other infrastructure. To achieve this will require compromises during the initial phases of laying out the infrastructure.

Utility line locations should be adjusted to accommodate a continuous tree planting trench that doubles as a stormwater filter and also promotes infiltration and permeability. Each project and site will have unique conditions requiring a thorough consideration of which best practices to select and promote to meet the guidelines.

Trees have many positive impacts on the environment and community. Their primary benefits include:

• Mitigating global warming by reducing Green House Gases (GHG)
  
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• Storing and sequestering carbon dioxide
  
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• Improving air quality
  
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• Removing pollution
  
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• Phytoremediation
  
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• Increasing energy savings (shade and windbreaks)
  
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• Reducing energy use in buildings when located to produce shade and windbreaks, thereby reducing carbon dioxide emissions from fossil-fuel based power plants
  
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• Reducing urban heat island effect
  
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• Reducing pavement temperature, which reduces the rate of asphalt deterioration
  
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• Intercepting rainfall
  
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• Stormwater rate control
  
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• Improving water quality
  
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• Facilitating stormwater ­infiltration and treatment
  

Additional benefits of urban trees include:

• Increased property values
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• Social and psychological benefits (offsets symptoms of ADD/learning disabilities)
  
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• Crime reduction
  
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• Increased aesthetics
  
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• Willingness of consumers to pay more for products in business districts with trees
  
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• Human health benefits
  
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• Wildlife habitat
  
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• Moderating temperature of water prior to entering natural water ­bodies
  
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• Creating micro-climates for humans along urban streets
  

With these benefits, trees are finally being realized as a critical component of the urban and suburban infrastructure. As such, consideration must be given and efforts made to strategically place trees to maximize their value and ensure their long-term success.

Equally important is selecting the right tree for a location to prevent future conflicts with infrastructure. On average, sidewalk, curb and gutter repair, and legal costs ranged from $3.70 in the Midwest to $11.22 in California, per tree on an annual basis. When repair costs for damaged sewer lines, building foundations, parking lots, and other hardscape items are included, Midwest cities spent more than $50 million per year rectifying root-sidewalk conflicts (Midwest Community Tree Guide: Benefits, Costs, and Strategic Planting. McPherson and others, August 2005). Therefore, proper planning and careful attention to tree and utility locations can translate into substantial savings over time.

Maximum benefits are accrued by incorporating best practices for achieving long-lived trees that improve air quality, wind (climate) control, and water quality and provide an increased annual net value to the community.

We encourage their use and hope that they will guide you to incorporate better design to protect, plant and maintain trees for their utility, environmental, economic and social benefits. SLDT

About the authors: Janette K. Monear, Executive Director, Texas Trees Foundation, past director, Tree Trust. Lorin W. Culver, ASLA, LEED AP, is a landscape architect and employed by Bonestroo.