Guidelines for Developing and Evaluating Tree Ordinances

Part 3. Evaluating the urban forest and ordinance performance

As we discussed in Developing a Community Forest Management Strategy, two stages in the urban forest planning process require the use of evaluation methods. To answer the questions "What do you have?" and "Are you getting what you want?", you will need to evaluate tree resources, management activities, and public attitudes. Thus, evaluation methods are important tools for formulating and monitoring tree management strategies. In these pages, we discuss how various methods and techniques can be used to evaluate tree resources and community forest management.

You can access our descriptions and examples of urban forest evaluation methods either from the list below or by following the links from the page on Goals for Community Forest Programs. Included in this section are methods for evaluating tree resources, urban forestry management activities, and public attitudes. Most of the techniques summarized here are well established, although a few new applications and adaptations for urban forestry are included. Where possible, we have provided examples to demonstrate actual applications of the techniques described. Please contact us if you know of other useful links or would like to see additional methods covered.

The key to successful and efficient evaluation lies in focusing on what needs to be evaluated. It is generally not desirable to collect more detailed information than is likely to be used, since cost and effort generally increase with the level of detail. On the other hand, it may be more efficient to collect a variety of data in a single evaluation than to conduct a series of separate evaluations. By following the process described under Developing a Community Forest Management Strategy you should be able to determine what types of data you will need to collect to meet your needs for information.

Methods for evaluating tree ordinances and the urban forest ecosystem

* Sampling from populations. In many cases, it will be more efficient to evaluate a sample of the population under study (trees, parking lots, homeowners) than to evaluate the entire population. Here we discuss how to develop a valid sampling scheme.
* Photogrammetry and remote sensing techniques. Using stock aerial photographs or other aerial imagery, photogrammetric techniques can be used to assess tree canopy cover quickly and cost-effectively. We discuss the uses of photogrammetry and provide some examples of applications to ordinance evaluation.
* Ground survey. For many applications, the ground survey is still the simplest and most accurate means for collecting detailed data on the urban forest. We describe basic ground survey methods and a number of typical applications.
* Photo points. Photographs taken from the ground or the air can provide graphic and obvious evidence of changes in tree condition and cover. We discuss some considerations for establishing effective, repeatable photo points.
* Record keeping and analysis. Well-maintained records and databases can be analyzed to provide a wealth of information on ordinance performance. We discuss the use of GIS, tree inventories, and other records.
* Public polling. People are an integral part of the urban forest ecosystem. We present a brief overview of methods used to assess the opinions of the proverbial person on the street.