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作者

来源

URBAN FORESTRY & URBAN GREENING,Vol.32,P.32-55

语言

英文

关键字

Ecosystem services; Forest monitoring; Impervious surfaces; Tree cover change; Urban forests; FOREST; CITIES

作者单位

[Nowak, David J.; Greenfield, Eric J.] US Forest Serv, USDA, Northern Res Stn, 5 Moon Lib,SUNY ESF, Syracuse, NY 13210 USA. Nowak, DJ (reprint author), US Forest Serv, USDA, Northern Res Stn, 5 Moon Lib,SUNY ESF, Syracuse, NY 13210 USA. E-Mail: dnowak@fs.fed.us; ejgreenfield@fs.fed.us

摘要

Paired aerial photographs were interpreted to assess recent changes (c. 2009-2014) in tree, impervious and other cover types within urban/community and urban land in all 50 United States and the District of Columbia. National results indicate that tree cover in urban/community areas of the United States is on the decline at a rate of about 175,000 acres per year, which corresponds to approximately 36 million trees per year. Estimated loss of benefits from trees in urban areas is conservatively valued at $96 million per year. Overall, for both urban and the broader urban/community areas, 23 states/districts had statistically significant declines in tree cover, 25 states had non-significant decreases or no change in tree cover, and three states showed a non-significant increase in tree cover. The most intensive change occurred within urban areas, with tree cover in these areas dropping one percent over the 5-year period, compared to a 0.7 percent drop in urban/community areas. States/districts with the greatest statistically significant annual decline in percent urban tree cover were: Oklahoma (-0.92%/yr), District of Columbia (-0.44%/yr), Rhode Island (-0.40%/yr), Oregon (-0.38%/yr) and Georgia (-0.37%/yr). Coinciding with the loss of tree cover was a gain in impervious cover, with impervious cover increasing 0.6 percent in urban/community areas and 1.0 percent in urban areas over the 5-year period. Such changes in cover types affect the benefits derived from urban forests and consequently the health and wellbeing of urban residents.