Connecting people with ecosystems in the 21st century: an assessment of our nation's urban forests

"Urban areas (cities, towns, villages, etc.) cover 3.5 percent of the 48 conterminous states and contain more than 75 percent of the population. In urban areas, about 3.8 billion trees cover 27.1 percent of the land. On a broader scale, metropolitan areas (urban counties) cover 24.5 percent of the conterminous United States and contain 74.4 billion trees that cover 33.4 percent of these counties. Between 1950 and 1990, metropolitan areas nearly tripled in size; urban areas doubled in size over the past 20 to 25 years. This report is the first national assessment of urban forest resources in the United States and details variations in urbanization and urban tree cover across the United States by state, county, and individual urban area. It illustrates local-scale variation, complexity, and connectedness of the urban forest resource and how this resource changes through time in response to a wide range of powerful forces. The report concludes by outlining future areas of emphasis that will facilitate comprehensive, adaptive, and sustainable urban forest management and improve environmental quality, enhance human health, and connect people with ecosystems in the 21st century." [Abstract]