In preparation for the San Francisco Urban Forest Plan (2013), the Planning Department performed an Urban Tree Canopy (UTC) Analysis using aerial imagery and additional data sets to determine a canopy estimate for the City & County of San Francisco. This analysis estimated San Francisco's tree canopy at 13.7%. This number supersedes a 2007 canopy estimate of 11.9% (USDA Forest Service, 2007). Given the differing methodologies used to arrive at these two numbers it is difficult to draw conclusions regarding urban forest growth or decline based on a comparison. The current analysis establishes a baseline and methodology from which future canopy analyses can be conducted and compared over subsequent years to track San Francisco's urban forest growth or decline over time. See the attachment under About for more on the methodology.