by DJ Nowak, EJ Greenfield
Urban Forestry & Urban Greening 11(1):21-302012
Paired aerial images from two different years (approximately 5 years apart) were compared for 20 U.S. cities. One thousand random points were laid over the images and classified by trained observers as woody vegetation, grass or herbaceous cover, bare soil, water, impervious (buildings), impervious (roads), or impervious (other). Nineteen cities showed a decrease in tree cover (average relative decrease of 5%). Only Syracuse, NY, showed an increase (relative increase 4%). Most of the lost tree cover converted to grass/herbaceous (47%) or to impervious (29%). Seventeen cities showed an increase in impervious cover (average relative increase 3.7%).