Urban Forestry

"There are about 60-to 200- million spaces along our city streets where trees could be planted. This translates to the potential to absorb 33 million more tons of CO2 every year, and saving $4 billion in energy costs."

- National Wildlife Federation
 
Urban forestry is defined as, "the art, science, and technology of managing trees and natural systems in and around urban areas for the health and well being of communities. Practitioners combine strategic planning and best management practices with environmental stewardship education to create sustainable, cost-effective solutions for our cities and towns."
 
These natural systems are not limited to parks and green spaces but include trees lining streets and private yards. However, the focus of discussions on urban forestry revolve around those trees and natural systems on public lands over which the governing jurisdiction can exert direct influence.
Trees provide economic and community benefits in addition to mitigating air and water pollution impacts. Below are listed some of the ways in which trees function as invaluable environmental assets. 

The benefits of urban forests are generally recognized to be found in three categories: environmental, economic, and cultural.

Environmental Benefits

  • Trees help to improve air quality by mitigating air pollution & greenhouse gases: Most trees use photosynthesis to convert carbon dioxide (CO2) into nutrients. That process helps to reduce the amount of CO2 which is a greenhouse gas and would otherwise contribute to smog and unhealthy conditions. However, the ability of trees to improve air quality significantly depends on many factors such as species, location, and the number of trees planted. While it can be difficult to quantify exactly how much air a particular tree improves, the US Department of Agriculture has found that one acre of forest absorbs six tons of carbon dioxide and puts out four tons of oxygen. This is enough to meet the annual needs of 18 people.
  • Trees help to reduce stormwater runoff and improve water quality: Stormwater runoff can be a big problem in urban environments. Large amounts of concrete and other impervious surfaces can force excess rainwater to pool in streets and on properties faster than the sewer system can absorb it. The result can be flash floods and damage to properties. Trees can capture large amounts of rain through their root systems and canopies, which also help to filter some of the pollutants. The net result is the redirection of rainwater into the ground water supply, and the improvement of water quality.
  • Trees help to reduce the urban heat island effect: If you have ever walked across an un-shaded parking lot during the hot summer, then you have experienced the urban heat island effect. Large areas of asphalt and concrete trap the heat of the sun and reflect it back into the environment, thereby raising the temperature in surrounding areas. The process contributes to smog, global warming and higher energy costs associated with increased air conditioning in buildings. The strategic placement of trees in and around parking lots and similar areas provide the shading necessary to limit the heat island effect.
  • Urban trees and forests help to reduce, and even eliminate, erosion: Arable soil can be lost to strong winds and stormwater runoff. The roots of trees bind to the soil and thus prevent soil loss.
  • Trees shelter wildlife and promote biodiversity: Environmental systems are complex and require the presence of a diverse range of bioforms. Trees provide a necessary habitat for a wide variety of wildlife that might otherwise have a difficult time living in our cities. A single oak tree, a species commonly found in many American cities, can support up to 500 species of insects and invertebrate species.
  • Healthy urban forests contribute to the stabilization of watersheds: Trees absorb large quantities of water through their root systems and thus help to mitigate flooding. Forest soil soak up and retain rainwater, which is released slowly over time. This effect occurs even during periods of low rainfall. Further, tree roots create air pockets within the oil which serve to filter contaminants which would otherwise enter groundwater sources (aquifers, streams, lakes, etc).

Economic Benefits

  • Trees increase property values: The USDA Forest Service has found that mature trees add an average of 10 percent to a property's value.
  • Businesses do better on tree lined streets: A 2004 study found that consumers overwhelmingly preferred business areas with well-planted canopy-covered streets and suggests a link to the amount of time that shoppers are willing to spend in stores.
  • Trees can reduce heating and cooling costs for buildings: When placed strategically around buildings, trees can reduce cooling costs by 30 percent, and heating costs by 20-50 percent. By providing shade and a barrier to wind, trees cool buildings during hot weather, and limit snow accumulations during cold weather. Economically this is beneficial as it can reduce the fuel costs associated with heating and cooling.
  • Crime rates tend to be lower in areas with trees: Research presented at the American Association for the Advancement of Science conference (AAAS) in Chicago socio-cultural benefits showed that the presence of trees could cut crime by as much as seven per cent.

Cultural Benefits

Cultural Ecosystem Services is the term used for the nonmaterial benefits for people. While these can be hard to quantify, they are essential for quality of life and overall wellbeing.

  • Trees help to define a 'sense of place' and provide desirable landscapes: The aesthetic benefit of trees is obvious. Their size and color can help to soften the often-harsh urban landscape. Perhaps less obvious are the ways in which trees can contribute to the 'sense of place' or unique characteristics that define our geographic communities. Species type, placement, and even long-standing individual trees can underscore regional history, culture, and identity.
  • Trees and urban forests encourage community interaction: People tend to gather more when green spaces are available.
  • Trees help to reduce noise pollution by absorbing and blocking urban noise: This has been shown to reduce stress for people living and working around trees
  • Habitats created by urban forests provide educational opportunities for people: Urban forests provide opportunities for environmental educational programs for both children and adults. Many schools have "outdoor classrooms" with curricula designed for the natural sciences.

Other Benefits

  • Tree lined streets can help improve road safety
  • Some studies have found trees lined streets promote safer driving by giving the impression of narrowing streets. They also provide a buffer between vehicles and pedestrians.
  • Tree planting can be a very valuable tool for reclaiming derelict land within cities
  • The management of vacant property is an ongoing problem for many local governments. Even during periods of economic prosperity, when residential and commercial real estate development is high, there often remain neglected lots and other open spaces that place a high demand on code enforcement, solid waste and other municipal services. Planting trees and shrubs can offer a cost-effective way to manage such properties on either a short- or long-term basis. 

Role of Stakeholders

Given the diverse number of benefits provided by trees and urban forests, it is little wonder urban forestry is increasingly recognized as a vital component of sustainable communities. Sustainability officers are in the opportunistic position of influencing policy, planning, and perception regarding how to better utilize a collaborative partnership with nature.
While determining how to better integrate the assets of trees and urban forests, a sustainability officer should recognize the importance of cooperative, productive relationships with the following stakeholders.

Elected Officials

For envisioning the potential of community and programs and for enacting legislation

Planning Departments

For creation of master plans, policies, and strategies where trees and urban forest lands are high level priority. For identifying incentives for private sector entities to include trees and urban forest components in their development projects. For developing and implementing conservation easements, land trusts, protection in perpetuity agreements, and transfer of development rights for creation of green space.

Public Works 

For advocating on the desirability of utilizing natural infrastructure - Stormwater management, Energy consumption/heat island effect reduction. For design, construction and maintenance of natural infrastructure, Including the urban canopy.

Transportation Departments

For planning and constructing greenway connections. For advocating and accommodating tree planting zones in road construction projects

Economic Development Departments

For advocating for the inclusion of trees and urban forests. For identifying incentives for private sector entities to include trees and urban forest components in their development projects. For developing funding mechanisms through which plantings and acquisitions are possible. For quantifying the local economic contributions of trees and urban forests. For including natural resources as a critical component of any economic development plan.

Parks and Recreation Departments 

For capitalizing on their inherent mandate to provide quality green spaces. For planting and maintaining the urban canopy. For engaging the community regarding the benefits of trees and urban forests.

Community Services Departments

For developing supplemental labor pools - Local "green collar" jobs programs, Corps. for National and Community Service. For engaging the community regarding the benefits of trees and urban forests.

Private Sector Organizations

Sometimes better positioned to envision and focus on a single mission. Better able to secure private donations than public sector. For engaging the community regarding the benefits of trees and urban forests.

Non-profit Organizations

For advocacy and strategic partnerships. For access to alternative funding sources. For volunteer and staff resources.

Risks and Challenges

Urban forestry can be subject to NIMBY (not in my backyard) arguments as people occasionally experience trees as a nuisance or as a cause for disputes between neighbors. Frequent citizen complaints include too much shade; leaf litter; low hanging and falling branches; undesirable seeds, pods or fruits; and bird droppings. Many of these objections can be overcome by good educational efforts and by careful selection, placement, and routine maintenance of trees. The benefits of trees in our communities far outweigh any real or perceived inconveniences. One area of concern is the damage to homes and buildings that can result from tree roots or falling trees. Cases of damage to building foundations from invasive roots are typically the result of improper siting of trees and buildings relative to each other. The young sapling planted by the front door today will be the giant oak of tomorrow with roots damaging walkways and foundation. Proper education about site and species selection is critical. Falling trees often result from unstable root systems and/or severe storms. It is important understand regional soil types and the routine maintenance necessary to promote healthy root systems and to reduce the other circumstances that would cause a tree to fall (disease, rotten wood, a too-heavy crown, etc). It is a good idea to work with local arborists, botanical gardens or other resources to achieve this goal. Of course, it is not possible to always forecast and prevent a tree from falling, nor can we stop severe weather. Thus, there is a clear case for having adequate building insurance to address unavoidable calamities.

Nonetheless, the damage from trees remains low in relation to the large number of trees and the many direct and indirect benefits they provide.

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