Urban Forestry

By: Ethan Crockett (email)

What is an urban forest and how do we benefit from it?

Why are trees important to everyone?

Trees, both indoors and outdoors provide humans with satisfactions and enhancement to their daily lives.  Children love to play around and climb on trees, while teenagers enjoy sitting under a tree in the shade, while adults may look forward to sharing the tradition of a family Christmas.  Studies have show that people of all ages benefit emotionally and physically from the presence of trees around their homes, offices, or schools.  Trees just have a way of making people feel good.

What is an Urban Forest? (Merriam-Webster)
           
            “Urban”- of or relating to a city
            “Forest”- “a dense growth of trees and underbrush covering a large tract”

An urban forest is the representation of trees amongst the streets, sidewalks, grasses, buildings, in a city environment.

What are the benefits of trees in an urban environment?

Where would you rather live?

Mature trees vs. Tree-less Landscape

“Landscapes featuring mature trees add value as well as beauty to the property”	“Landscapes featuring mature trees add value as well as beauty to the property”
"Treeless landscapes often have a barren and undesirable appearance"	"Treeless landscapes often have a barren and undesirable appearance"

Aside from just the sheer beauty and aesthetic quality that trees can add to a landscape, trees add value to urban landscapes.  Mature trees in a yard have the ability to increase property value by as much as 15%!

Trees also have the ability to improve the environment!  Trees absorb carbon monoxide and produce healthy atmospheric oxygen for humans to breath.  Through shading and transpiration, trees cool the air.  Transpiration is the process in which water is evaporated from the leaves of trees.  Finally, trees in the urban environment are know for their trait of improving water quality.  With roots systems distributed throughout soil horizons, soil is going to be much less likely to wash away during a heavy downpour or storm.

Having large landscape trees around the home can also provide temperature control and regulation to reduce winter heating costs and summer cooling costs.  In Virginia, the canopy of a deciduous tree planted in front of a southeast facing window would provide excellent morning shade during the summer months.  To provide afternoon shade, as the sun is setting a tree would need to be planted in front of a southeast-facing window.  By planting a deciduous (broadleaf) tree, the tree would lose its leaves during the cold winter months, allowing the sun to pass through the canopy and heat the interior of the home or building.  During the summer, however, a full canopy of leaves would prevent sunlight from increasing temperatures inside.  As a result, the homeowner’s heating and cooling bills decrease.

Barriers

Trees in urban landscapes are often planted, cultivated, or left to be visual or acoustic barriers.  Just as this concrete sound barrier is built to block road noise from the highway, trees have the ability to reduce sound penetration as well. 

"Concrete highway sound barrier"

As seen below in this aerial photograph, a small forest was left between this community and the highway in order to reduce noise from the highway.

Aerial Photograph courtesy of Google Maps; Midlothian, VA

In this situation, evergreen species are often the favorable species, due to their year-round cover qualities.  Many environmentalists encourage the use of trees over large caoncrete sound barriers for their aesthetic qualities, as well as environmental benefits.

On a smaller scale, citizens often plant trees as visual or privacy barriers.  Once again, evergreens are the commonly used species.  As you can see, these two next-door neighbors likely planted these trees when they were young; now they serve as a year-round privacy fence between the properties.

Value of Trees

Trees have been proven to be beneficial in the urban environment, especially when pertaining to the following categories:

• Runoff Reduction
• Pollution Reduction
• Carbon Sequestration (removal or separation from atmosphere)

The Virginia Cooperative Extension has developed methods to calculate and assign dollar values to each of these properties, based on diameter at breast height.  Find the dollar value of trees in your yard!

Cost/Benefit analysis can be calculated using the following equations:

• Runoff reduction: $ value = 0.0303*(DBH)2 + 0.182*(DBH) + 2.29
• Pollution reduction: $ value = 0.16*(DBH)2 – 0.334*(DBH) +2.57
• Carbon Sequestration: $ value = 0.027*(DBH)2 – 0.095*(DBH) + 6.85

For more information, visit: http://www.ext.vt.edu/pubs/forestry/420-181/420-181.html

Trees providing positive value in a landscape are to a definite advantage, however, when citizens do not care for trees, they often die!  Removing a large dead tree can be very costly, so its important to keep them healthy!  Many commercial tree care companies charge as much as $70 per man, per hour.  With a three-man tree crew on your property for one full work day, the price tag will be over $1500!

Urban Tree Establishment

Citizens interested in adding new trees to their landscapes should take interest in their goal before purchasing the new trees or shrubs.   Arborists use the guiding principle of “right tree, right place,” when it comes to tree selection for a landscape. Research should be done in order to know: survival rates in different environments, average rooting depths, average tree heights, mature form, diseases that could affect the tree, and many other aspects about the life cycles of the species you desire to plant. 
A daily battle of utility arborists deals with pruning tall-growth species that have been plant beneath overhead power lines.  When tree limbs contact high voltage power lines, generally damage is done to the tree, and power outages result.  

"Trees often pose as conflicts to utility lines"

This is easily prevented by planting utility friendly species from the start.  Utility friendly tree species are trees that have maximum heights of less than 30 feet, therefore they will not grow into the overhead lines. 

In the same aspect, trees become nuisances to building inspectors and homeowners when they are planted too close to the building.  Trees with large root systems have the ability to disrupt an entire building foundation, making a building by-code, unstable.  In this situation, it may have been better to not plant a tree at all.  Therefore, planning and educating yourself about landscape trees prior to planting may prevent unsightly problems in the future.