Agenda - Planning Commission - 10/04/2012

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to the early 199os in a study for the Journal of Arboriculture entitled "Assessing the Benefits and Costs of the Urban Forest" (Dwyer, McPherson, Schroeder, and Rowntree 1992), which documented the fol- lowing economic benefits: ® increased property values; ® increased tax revenue; ® reduced building energy costs (by block- ing wind and providing shade); ® reduced stormwater impacts and related costs; and ® Improved health and lower health care costs. URBAN FORESTRY IN DEVELOPMENT CODES Given the strong social, ecological, and eco- nomic benefits of trees, communities should regard urban forest protection and enhance- ment as an investment that needs to be effectively managed over time. To this end, many cities and counties have adopted long- term urban forestry plans and added forestry provisions in their development regulations to manage and protect this critical resource. Recognizing the range in benefits and return on investment of the urban forest, many municipalities have adopted regula- tions to ensure the preservation and replen- ishment of their tree canopy. Successful tree preservation ordinances consider the triple bottom line benefits of urban forestrythat are most meaningful to their community. Tree protection standards will be most effective when based on goals and objectives that vary based on each community's unique conditions, yet there are common elements that can be found among municipalities with robust tree protection standards. Statement of Purpose and Intent The statement of purpose should be clear and concise, and is ideally based on the goals and objectives of an urban forestry master plan, green infrastructure plan, or urban forest element of the comprehensive plan. These objectives should enumerate the social, environmental, and financial benefits of tree preservation that justify a significant investment by the community. Applicability Tree ordinances generally come in two differ- ent categories: those that apply only to trees on public property (i.e., street trees) and those that apply to development on private Recognizing the range in benefits and return on investment of the urban forest, many municipalities have adopted regulations to ensure the preservation and replenishment of their tree canopy property. In most cases a municipality will not attempt to preserve or replace all trees everywhere to avoid placing a significant financial burden on individual home owners and the city's resources for enforcement and maintenance. In general, individual residen- tial lots, developed lots, or properties under a certain size threshold are exempt from the regulations, although there are some excep- tions depending on the circumstances of the community. Atlanta, for example, places preeminent value on its tree canopy because of its humid subtropical climate and recent substantial tree loss from development prac- tices. With one of the most aggressive tree protection ordinances in the country, Atlanta requires a permit to remove healthy trees above a certain size threshold on any prop- erty of any size. While this approach has been successful in helping to maintain tree canopy for this large city, most communities must be more selective to maximize the effectiveness and benefits of tree preservation regulations. Minimum Tree Coverage or Density Requirements Typical tree ordinances establish a minimum number or percentage of trees of a given size, usually measured as diameter at breast height (dbh), which must be protected or planted on a site. Some communities apply a minimum percent tree canopy require- ment that emphasizes the preservation of stands or clusters of mature trees, rather than individual trees. Existing tree canopy is considered more socially, economically, and environmentally beneficial because of the fully realized shade quality and root struc- ture. By placing higher value on tree canopy, communities have a better probability of promoting preservation over planting of trees that could take years to mature. Fairfax County, Virginia, regulates tree canopy cov- erage based on ao-year tree canopy require- ments (percentage of site to be covered by tree canopy in io years) that vary by zoning district. The ordinance requires that all ef- forts be made to preserve the existing tree canopy; however, any portion of the tree canopy requirement that cannot first be met through the preservation of trees can be provided through tree planting. Protection of Special Trees Many communities apply special regula- tions to trees that they consider to have ® In addition to providing shade, trees intercept rainwater. ZONINGPRACTICE 9.12 AMERICAN PLANNING ASSOCIATION' page 4