BENEFITS OF LARGE-TREE URBAN FORESTRY
A position paper: Energy Policy Task Force, Outcomes of a Good Energy Policy Sub-Committee: Urban Heat Index and Large Scale Trees
Submitted by Deborah Langhoff June 2007 to the New Orleans City Council's Task Force
The replacement of natural ground cover with pavement and buildings as part of urban development significantly alters the surrounding microclimate. The elimination of large-scale forestry results in increased energy consumption in heating and air conditioning, decreased natural drainage, increased air and water pollution, and decreased quality of life. In New Orleans, these consequences of urbanization have been exacerbated by the sweeping deforestation caused by Hurricane Katrina. Planting large-scale trees is a relatively easy and affordable long-term investment that can be made in the community, significantly reversing the negative effects of urban development on the microclimate and offsetting the community’s carbon footprint.
To use the opportunity for city-wide urban forestry development to encourage the replanting of large-scale local species. To educate the public on the economic and environmental benefits of large-scale planting as opposed to small-scale ornamental planting. To focus alterations to codes and zoning regulations on incentives for those who include large-scale trees in their landscaping. To steer public planting projects toward native and large-scale trees. To revise regulations, requiring substantial square-footage of large-scale planting in parking lots and other developed public spaces.
The Problems of Tree-less Urbanization
An urban heat island is an area in which air and surface temperatures are significantly higher than in surrounding rural areas. This effect is created and intensified as the pavement, buildings, and other infrastructure of urban development replace the natural land cover. There are three primary ways in which urban developments alters the microclimate of an area. First, the displacement of trees and vegetation minimizes the natural cooling effects of shading and evaporation of water from soil and leaves. Second, tall buildings and narrow streets reduce airflow and trap warmer air near the ground. Third, waste heat from vehicles, industry, and air conditioners adds warmth to the surrounding area.
The EPA recommends planting trees and vegetation as a simple and effective way to mitigate the heat island effect, through both widespread planting in a city (decreasing local air and surface temperatures) and strategic planting around individual homes and buildings (reducing individual energy costs and peak energy demand).
Trees and vegetation naturally cool the air in two major ways: by providing shade and through evapotranspiration (the evaporation of water from leaves). Shaded walls may be 9 to 36 degrees F cooler than unshaded surfaces, reducing the air conditioning costs for the shaded building. Additionally, the cooler surfaces lessen the heat island effect by reducing heat transfer to the surrounding air. Evapotranspiration is a process that uses heat from the air to convert water contained in the vegetation into water vapor, thereby reducing the air temperature (though increasing air moisture). As a mature tree transpires approximately 40 gallons of water per day, this process alone can result in peak summer temperature reductions of 2 to 9 degrees F.[i] In the winter, trunks and branches shield nearby structures from the wind, while the leaves have fallen off, allowing the sunlight to reach the building, significantly reducing heating costs,
In addition to these energy savings, an average tree stores 13 lbs of carbon per year. According to the U.S. Dept of Agriculture, one acre of forest absorbs six tons of carbon dioxide and puts out four tons of oxygen – enough to meet the annual needs of 18 people. Planting large trees – which process much more carbon dioxide than smaller trees – is crucial to reducing our carbon footprint. Furthermore, leaves and roots are natural filters, which remove pollutants such as ozone, carbon monoxide, and sulfur dioxide from the air and water.
Urban Forestry – Progressive Beautification
Many urban areas across the country have instituted planting programs in order to combat the microclimatological effects of the heat island phenomenon, reduce energy consumption and costs, to provide increased drainage, to decrease erosion, to reduce pollution, and to increase property value and quality of life.[ii]
Replanting the tens of thousands of trees lost in Hurricane Katrina is an opportunity to plant large-scale, local species that will flourish, such as live oak, bald cypress, red maple, and black gum, as suggested by the National Arbor Day Foundation for the New Orleans area. The Katrina Free Tree Giveaway has been successful in distributing over 5,000 seedlings of these local large species through generous donation from the National Arbor Day Foundation in cooperation with the National Audubon Society. This effort has also been reflected in the Sierra Club program that focuses on reestablishing bald cypress growth to stabilize costal wetlands.
A community-building program can be adopted that brings an urban forestry perspective into every development and includes beauty along with environmental considerations.
Currently, the City Department of Parks and Parkways provides an online guide for those who wish to plant street trees on the public property adjacent to their private property.[iii] This guide focuses on choosing the type of tree that is appropriate to the space available. While space considerations are obviously important, this guide should be expanded to include information on the benefits of large-scale and native trees in particular.
With regard to widespread plantings on public property, the New Orleans Department of Parks and Parkways states: “to restore our grand boulevards, we are developing master plans and seeking funding to replant neutral grounds devastated by the hurricane.”[iv] Neutral ground replanting should focus specifically on the large-scale native trees that are far more beneficial than smaller ornamentals.
Specific changes to current regulations should include zoned square-footage requirements for large-scale trees in parking lots in which non-compliance results in annual penalties in the form of a directed levy earmarked for coastal cypress forestry. Also, zoning guidelines should include incentives for large-scale trees beneficially placed in mixed-use and mixed-income developments. Additionally, incentives should encourage the use of landscaped trees and ponds to improve natural drainage. An essential component of this effort is public education on the energy savings benefits of including large-scale trees in residential planning.
Economic Impact of Urban Forestry
Lower energy costs for individual homes, businesses, and municipal buildings
“Trees properly placed around buildings can reduce air conditioning needs by 30% and save 20-50% in energy used in heating.” (USDAForest Service)
Increased property value for landscaped properties
“Healthy trees add an average of 10% to a property’s value.” (USDAForest Service)
Increased revenue for landscaped business districts
“Consumers will shop longer and more frequently in downtown business districts with trees and other landscaping, and are willing to pay more for parking and up to 11% more for goods and services in such areas.” (University of Washington)
Cost-benefit estimate comparison[v]
Annual benefits for a large-scale urban tree
Total benefits/year = $55
Total costs/year = $18
Net benefits/year = $37
Life expectancy = 120 years
Lifetime benefits = $6,660
Lifetime costs = $2,160
Value to community = $4,440
Annual benefits for a small-scale urban tree
Total benefits/year = $23
Total costs/year = $14
Net benefits/year = $9
Life expectancy = 30 years
Lifetime benefits = $690
Lifetime costs = $420
Value to community = $270
Planned urban forestry will substantially increase quality of life in New Orleans. Trees promote the general well-being of a community. They reduce stress, noise pollution, exposure to harmful ultraviolet light, and exposure to harmful air and water pollution. Trees create walkable sidewalks, drawing people outdoors, thereby increasing public surveillance and civic empowerment and preventing crime.
Also, it is clear that landscaping that includes large-scale trees is beneficial to local commerce, both by reducing energy costs and attracting business.
Large-scale tree planting is an extremely affordable approach to energy conservation. The costs of planting and maintaining large-scale trees are far less than the returned benefits in the form of lowered energy costs, decreased pollution, and increased property value...
[ii] Baton Rouge Green’s new native tree planting map and guide http://www.urbanforestry.subr.edu/green/index.htm
Chicago Green Roof Initiative http://www.artic.edu/webspaces/greeninitiatives/greenroofs/main.htm
Atlanta in cooperation with NASA http://www.coolcommunities.org/
Toronto’s CoolToronto http://www.cleanairpartnership.org/cool_toronto.htm
Baltimore Trees Clean Bay http://www.bayjournal.com/article.cfm?article=2948
Sacramento Municipal Utilities District Tree Benefits Estimator http://usage.smud.org/treebenefit/
Seattle - creating natural drainage systems using trees, vegetation and small ponds http://www.seattle.gov/util/About_SPU/Drainage_&_Sewer_System/Natural_Drainage_Systems/Natural_Drainage_Overview/index.asp
[v] http://www.urbanforestrysouth.org/Resources/Library/the-large-tree-argument-1-up/view Hypothetical case using data for trees at year 30, projected to life expectancy from McPherson, E.G.; et. al. 2003. Northern mountain and prairie community tree guide: benefits, costs, and strategic planting. Center for Urban Forest Research, Pacific Southwest Research Station, USDA Forest Service. 92 p.
Katrina Free Tree Giveaway Campaign
On November 18, 2006 in New Orleans City Park near Popp's Bandstand, LaRoots volunteers with the able assistance of local Girl Scouts distributed 1100 bald cypress, black gum, red oak, and red maple trees to New Orleanians from several parishes who are eager to restore the urban tree canopy. A limit of five trees per person was established to accommodate the overwhelming number of participants. Special appreciation to Dr. Mark LaSalle of Audubon Mississippi for organizing this first Giveaway, to WDSU for their coverage, and to City Park for offering Popps Bandstand for the distribution.
On March 17, 2007 a new shipment of 4,000 similar seedlings arrived and with the cooperation of Save-A-Center on Carrollton Avenue, were kept refrigerated and available for distribution, which Deborah completed, with the last 1,000 given away at the Festival of Neighborhoods at the Superdome's Home Show.
Trees & Native Plants
70% of our urban tree canopy was lost during Katrina. Homeowners can take individual responsibility to replant this fall with trees that showed resilience to storm conditions.
Live Oaks weather storm conditions better than other species. Young oaks grow quickly, and slow down as the tree matures. Plant Live Oaks in large yards, parks, and neutral grounds where its canopy will spread unimpeded. A friend recently noted, “Plant a live oak and you’re planting for the next 500 years!”
Bald Cypress prove strong in winds and are suitable to plant in yards where they do well in areas of slower drainage.
Crepe Myrtles generally survived Katrina flood waters and are useful in smaller areas, near homes, driveways, and buildings.
“Out on a Limb” in The Times Picayune examines specific species and cautions against a “chainsaw revenge” phenomenon, where homeowners remove healthy trees in an effort to protect property from future storms. The article further outlines how a proper tree canopy lessens storm conditions and protects our homes during hurricanes. http://www.nola.com/news/t-p/frontpage/index.ssf?/base/news-6/1158476119165140.xml&coll=1&thispage=1
Native Plantings: Natives help migratory birds and are suited to local conditions. Many of the plants considered traditional in New Orleans are actually exotics that were brought here generations ago. While they have adapted to our area, remember to include true native species in landscapes. An extensive list, planting tips and history, are part of Charlotte Seidenberg’s “The New Orleans Garden” (1990). A few from that source for this brief list…
Deciduous Trees: red maple, river birch, pecan (not too near the house), hackberry, dogwood, persimmon, silver bell, mulberry, bald cypress, black willow
Deciduous Shrubs: buckeye, hydrangea, azalea, elderberry, bridal wreath, blueberry
Evergreen Trees: bay, magnolia, pine, oak
Evergreen Schrubs: acacia, American holly, yaupon, star anise, southern wax myrtle. Louisiana palmetto, maidenhair fern, and cinnamon fern are popular.
Night Skies Initiative
Outdoor Lighting: Can you see the Milky Way tonight? Many of our children have never seen it. 97% of all Americans live in areas that never really darken.
New Orleans neighborhoods were dark for too long after hurricane Katrina but what many residents who returned early often commented on was a night sky with stars. As we restore our neighborhoods, a single consideration can help our natural world -
Up-lighting or Down-lighting?
The absence of darkness erases much of our world’s celestial beauty. Light pollution confuses migratory bird flocks which fly to their death by the tens of thousands at a time, and it may affect human hormonal rhythms and associated diseases. Artificially lighting our cities is a way of life, but there are ways to direct outdoor light back down to Earth, where it is needed instead of up into the night skies.
End Cypress Mulch
On December 1, 2006, LaRoots joined the campaign to seek alternatives to Cypress Mulch as we rebuild our residential and commercial landscapes. Louisiana needs every cypress tree it has and cypress trees that are logged will not be replaced by mature trees soon enough to warrant their destruction. Local alternatives include shredded tires, pine needles, and pine bark.