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Sustainable Tree Ordinances, Part I

By LASN associate editor Prof. Buck Abbey, ASLA, CELA, Robert Reich School of Landscape Architecture, Louisiana State University






Santa Monica measures the percent of tree canopy coverage by neighborhood and by land use. Public officials also measure the percent of newly planted and total number of trees that meet defined sustainability criteria. The target for tree canopy is to reach a minimum goal of 18 percent canopy coverage within residential areas and 25 percent canopy coverage within commercial areas of the city.


Editor's note: This column and next month's part 2 is derivative of a larger paper Buck Abbey will present at the American Forests' 2008 National Conference on Urban Ecosystems in Orlando (May 26-28). Thanks for the preview, Buck!

Tree ordinances are about to enter a new era. There are trends being initiated to make these urban forestry tools based in part on sustainable practices.






Santa Monica's community forest comprises 33,500 trees located in public areas throughout the community. People take their trees seriously here. A streetscape project in the city that proposed to remove 54 mature ficus trees resulted in the Treesavers group going to court and getting a temporary restraining order against the city removing the trees. (See p. 117 of LASN's April online magazine for story.)


Green Cities

Frederick Law Olmsted (1822-1913), writer, urban visionary, park planner and founder of landscape architecture in the U.S. realized early in his career that for a city to be sustainable, it must have adequate open spaces, clean air and a wholesome environment flanked by trees, meadows, streams and opportunities for recreation and social gathering. Olmsted was one of the first to recognize that if cities are to be sustainable, they must be designed using native plant materials and natural processes that will stand up to time and the temptation of age to weather and fail. He relied upon trees and the urban forests in his many parks and principal urban spaces of cities across the nation to provide elements of nature that are truly sustainable. Nature in the city does work and provides ecosystem services. This is the reason Central Park (1858) in New York has survived most buildings and social institutions of its age. The landscape will sustain itself.

Sustainability is defined as design, construction, operations and maintenance practices that meet the needs of the present without compromising the ability of future generations to meet their own needs (ASLA 2007). Green infrastructure, as noted by Olmsted, is the key to building green cities.






Frederick Law Olmsted recognized that for cities to be sustainable they must be designed using native plant materials and natural processes that will stand up to time and the temptation of age to weather and fail.
Photo is of a bronze casting of Frederick Law Olmsted by Beij, Williams and Zito Inc., Hartford, Conn.


Sustainability in the Urban Forest

New Yorkers realize the future of this great American city is based on making the city livable while meeting the challenges posed by an environment under stress due to growth and development. To meet these challenges New York City has adopted a sustainability plan, dubbed Planyc. Mayor Michael Bloomberg and the city planning department staff have prepared a plan to green the city. Urban forestry plays a significant role in this plan.

Some 127 new initiatives are underway including several that will produce a sustainable urban forest. These initiatives include greening parking lot, incentives for green roofs, protecting wetlands and using storm water BMPs to clean urban runoff.

One of the first initiatives to be implemented is New York's recently adopted, and first ever, landscape code (see the March ordinance column in LASN's online magazine, p. 20). The landscape code provides standards for parking lot design, street yard garden design, enhanced open space standards, buffer yards and standards for on-site storm water management.

Other sustainable practices in this city of eight million citizens include greening the cityscape, adding additional open space, public parks, playground, multipurpose fields, "blueways," "greenstreets" and public plazas so that no resident lives more than 10 minutes from public forested areas. Part of this innovative city plan is to increase tree plantings to the 5.2 million existing trees in the city on both private land, within parks and along public streets. All parking lots in the city will be planted with trees and outfitted with micro-drainage facilities. The Planyc also envisions that all city streets especially in neighborhoods will be planted expectation to achieve 100 percent "stocking" by the year 2030. Over a million trees will be planted at the rate of 20,500 per year at an annual cost of $17 million.



"The big trees are in a dense forest....the grandest tall trees you ever saw.."--Frederick Law Olmsted, describing the Mariposa Big Tree Grove, 1863



The Sustainable City

Cities must not only have a sustainability plan as we have seen in New York City, but must adopt community policy by ordinance as well. In this regard, there may be no better city to examine than Santa Monica, California, a city of 84,000, to see how urban forestry is central to a sustainable city.

Santa Monica’s community forest is comprised of 33,500 trees located in public areas throughout the community. Two hundred different species are present with the most prevalent species being Washingtonia sp and ficus sp. Trees in this community include broadleaf evergreens, broadleaf deciduous, conifers and palms. The latter contributes most significantly to the urban forest canopy of this 8.3 square mile community. The urban forest is measurable so in this community there is one public tree for every two and one half citizens. Thousands of other trees grow on privately owned land in back yards and commercial properties. Forest management in Santa Monica includes tree planting, inspection, trimming and removal. The existing tree ordinance and technical tree manual provides information to developers and builders for tree protection during construction on private property.

This community forest brings the benefits of shade in the summer, sanctuary for urban wildlife, reductions in air and water pollution and increased property values, all central to achieving the objectives of the sustainable city program. San Monica touts itself as the "sustainable city" and has been working to make the city impact neutral for several decades. This community has set a variety of policies that will lead the city to a sustainable future. Among other initiatives, this community has policy that implements sustainable urban forestry.

Policy and administrative procedures for urban forestry practices are found under the topics "resource conservation," "open space" and "land use." With each sustainable topic, the city has established goals, indicators and targets for performance. The have developed a sustainability plan and monitor success on a periodic basis.

Sustainability Metrics

Urban forestry sustainability metrics are built around several factors that include green building and tree protection, accessibility to open space and parks, trees, storm water management, irrigation control and use of regionally appropriate vegetation. The sustainable urban forestry goal in this west coast city is to develop and maintain a sufficient open space system so that it is diverse in uses and opportunities and includes natural function/wildlife habitat as well as passive and active recreation with an equitable distribution of parks, trees and pathways throughout the community. The key to having a successful urban forest is having ample public open space supplemented by private wooded lands. Tax incentives could be used to allow land along streams, on steep slopes and in other sensitive environmental areas to remain undeveloped.

Santa Monica measures the percent of tree canopy coverage by neighborhood and by land use. This inventory is essential in understanding the composition and management needs of the urban forest (American Forests 2008). Public officials also measure the percent of newly planted and total number of trees that meet defined sustainability criteria. The target for tree canopy is to have an upward trend in the percentage of tree cover throughout the community and to reach a minimum goal of 18 percent canopy coverage within residential areas and 25 percent canopy coverage within commercial areas of the city.

According to the Santa Monica tree law, Sec. 7.40.010 [http://qcode.us/codes/santamonica/ qcode.us/codes] a minimum of two canopy trees shall be provided in the front yard setback and three canopy trees shall be provided in the side yard.

The community landscape code, Part 9.04.10.04 is a second measure of urban forestry sustainability and an important tool for creating a sustainable landscape. All areas of a development site not covered by buildings, driveways and sidewalks must be landscaped. This code sets design standards for drought tolerant landscaping and the use of appropriate plants based upon adaptability of the climate and topographical conditions of the building site.






D.G. "Buck" Abbey, Associate Professor of Landscape Architecture at Louisiana State University, is LASN's Associate Editor for Ordinances.




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December 14, 2019, 7:53 am PDT

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