Zoning Practice — August 2006

Ask the Author

Here are reader questions answered by Christopher Duerksen, who authored the July 2006 Zoning Practice article "Got Trees?" together with Molly Mowery and Michele McGlyn.

Question from Keith Holdsworth, Indianapolis:

Indianapolis is looking into using a percent tree cover technique for tree preservation. Can you give us some guidance on an appropriate way to choose the right percentage for us? We do think that the percentage is different for different land uses.

Answer from author Chris Duerksen:

An increasing number of communities are using the percent tree cover approach as their primary tool to protect trees. In brief, such regulations typically require that a certain percentage of tree canopy on a site be protected and set aside from any development. Fairfax County, Virginia, just outside Washington, D.C., was one of the first to utilize this approach on a jurisdiction-wide basis. It put in place a sliding-scale system that requires 10 percent minimum cover retention on industrial/commercial zone lands, 15 percent on high-density residential, and 20 percent on low-density residential. New ordinances have increased these requirements in many communities. For example, Franklin, Tennessee, a fast-growing, progressive community south of Nashville, is considering a provision that requires over 50 percent of tree cover to be maintained on some sites. The Franklin system is further distinguished by the fact that the percentage of tree cover required to be maintained is higher the less tree cover there is on the site to begin with. In other words, for example, a commercial site with 80-100 percent existing cover would have to protect 15 percent of that canopy. However, if that same site had only 15 percent existing cover, 26 percent would have to be protected. The percentage that is right for any community will depend on a number of factors including relationship to environmental and aesthetic goals, storm water management issues, and economic considerations, among others.

The major advantage of the tree canopy retention approach over some earlier techniques (such as protecting all trees larger than a specified size) is that the development review analysis typically can be accomplished by using aerial photographs and other readily available site information rather than undertaking a more detailed site tree survey that can be costly and time-consuming.

A key issue in making the tree canopy retention approach work is to give local planners guidance as to where on the site the trees should be protected. Effective ordinances not only give planners guidance in this regard (e.g., give priority to sensitive environmental areas, areas with specimen trees, etc.), but also some authority to require applicants to locate tree-save areas in those locations.

For further reference, see APA Planning Advisory Service Report No. 446, Tree Conservation Ordinances, at p. 40.

Question from Cynthia Camacho, Earth Tech, Raleigh:

I am working on a coastal land-use plan for a community in North Carolina. New development is taking out a lot of large live oak trees that residents are very concerned about. A tree protection ordinance was enacted but soon revoked. It was very controversial. I would like to provide the town with implementation strategies. Might incentives be a better approach? Do you have examples?

Answer from author Chris Duerksen:

Tree conservation ordinances are much more common and less controversial than 20 years ago — when few communities had them in place. However, they can still create an uproar, particularly in jurisdictions where developers do not have much experience with them.

In those instances, education is often an important approach. Both the Urban Land Institute and the National Association of Home Builders have publications and articles that document the value of protecting trees, with examples of developers who have built very successful developments that had tree conservation as an important guiding principle. Once local developers begin to understand they can make a profit and compete better by protecting trees, they often support tree conservation regulations.

If a straight regulatory approach is unlikely to succeed, then incentives can be crafted that may be successful in some instances. For example, many communities give credit toward landscaping requirements for any mature trees that are protected — and sometimes sweeten the pot by giving two- or three-for-one credit (preserve one big tree and get credit for three smaller trees required by landscaping regulations). Other communities try to take the "sting" out of tree protection regulations by allowing developers to mitigate by replanting an equivalent amount of tree caliper for any removed or payment into a tree planting fund to allow the locality to plant trees off site (e.g., Clayton, Missouri). In the final analysis, however, incentives will not assure protection.

Question from Murray H. Van Eman, Vice Chair, San Antonio Planning Commission:

What is the relationship between tree preservation and water conservation? Currently we are under water restrictions and they may get worse with so many 100 degree days and no rain in sight. Some have suggested that tree preservation and water conservation are, on some level, competing goals, especially since certain species consume so much more water than others.Water conservationfolks have even suggested that we stop watering our lawns altogether. Tree preservationists prefer stricter requirements, save more trees, especially heritage trees, and mitigate all tress that were cut down for development.

Answer from author Chris Duerksen:

While on its face, there may seem to be some tension between tree conservation and water conservation, many communities are recognizing in reality they are actually very complementary. Of course, if a jurisdiction with a dry climate allows planting of blue grass and non-native ornamental species that are water hogs, conflicts are likely to arise. But modern tree protection and landscaping ordinances will usually focus on protection of native species which often are, by definition, adapted to the local climate and do not need buckets of water. They also do not allow planting of species that will require heavy irrigation. Model water conserving landscaping codes have recently been published in drier states like Colorado and Arizona that can serve as good guides.

In a growing number of communities such as Austin, Texas, constituencies concerned with water conservation and water quality are often the biggest supporters of tree and vegetation protection ordinances. Numerous studies document that protecting trees is a very cost-effective way to protect water quality as well as actually conserving water by reducing storm water runoff and giving rain a chance to percolate into the soil. Similarly, studies also show that drought-resistant trees provide "free" air conditioning through shade, saving significant amounts of water that must be used to produce electricity for air conditioning on hot days. They also reduce the need to water lawns under those trees as experience in California during droughts has shown.

Question from Keith Bartholomew, Assistant Professor, College of Architecture and Planning, University of Utah:

In the last paragraph of your article before the conclusion, you state that "The next wave we can expect to see at the local level regarding carbon budgets will draw on precedents from European cities that require any additional carbon dioxide emissions associated with a development project (e.g., increased traffic) to be offset by tree protection or tree planting, both on- and off-site." Do you have citations to some of those European examples?

Answer from author Chris Duerksen:

The European examples were discussed by an international speaker at a recent sustainable community symposium hosted by the Sopris Foundation in Aspen, Colorado. We are tracking down the speaker's contact information for you. There is much going on across the Atlantic in this regard. For example, England's Sustainable Development Commission has recently recommended to the central government that it seriously consider setting up a carbon budget system across the whole economy, including businesses (See www.sd-commission.org.uk.). While we seem to be lagging behind in the U.S., some communities such as Aspen, Colorado, are taking ambitious steps to deal with carbon dioxide emissions and climate change. The city's Canary Initiative has a feature that allows citizens of the community to calculate their "carbon footprint." It would not be a major conceptual step to require major developments to do the same and then undertake mitigation measures.