Track Outcomes, Not Just Outputs
Counting trees or measuring overall canopy growth is one way to show progress. Also, increases in trees planted, volunteer hours donated, community groups engaged, parkland expansions, and a host of other program metrics, can show progress.
While progress in these areas may satisfy professionals in the field, others may want to measure movement toward the economic, environmental, and social objectives promised in the original plan. It is important to demonstrate progress towards both outputs (e.g. trees planted) and outcomes (e.g. less runoff, increased property value, and public health improvements)
While measuring tree plantings and canopy growth is not an easy task, tracking the functional benefits derived from new trees and expanded canopy demands even more time and resources. In fact, years may pass before indicators show movement. But initial plans should provide for periodic reviews that capture the multiple values of healthy urban forests. The U.S. Forest Service, academic and private researchers are already working on ways to easily link these outcome indicators to program outputs.
 Michael Leff of the Davey Institute and the US Forest Service has developed a comprehensive list of program metrics that encompass canopy, size class and species distribution, agency cooperation, private engagement and collaboration, environmental justice, resilience and regional collaboration, among other indicators.
 This remains a primary focus of Leff’s current work at the USFS Philadelphia Field Station.