Fragmentation is a continuing threat to the sustainability of forests in the Eastern United States, where land use changes supporting a growing human population are the primary driver of forest fragmentation (Stein and others 2009). While once mostly forested, approximately 40 percent of the original forest area has been converted to other land uses, and most of the remainder is not original forest (Smith and others 2009). The direct loss of forest land is an obvious threat; less obvious are the threats posed by isolation and edge which encompass a wide range of negative biotic and abiotic influences on remnant forest (e.g., Forman and Alexander 1998, Harper and others 2005, Laurance 2008, Murcia 1995, Ries and others 2004). Landcover data from 1992 indicated that forest tended to be dominant and well-connected where it occurred, but also that fragmentation was so pervasive that only 10 percent of the eastern forest area was not fragmented at a landscape scale of 66 ha, and that at least 40 percent of forest area was within 90 m of forest edge (Riitters and others 2002, 2004). Between 1992 and 2001, there was a net loss of interior forest in the east, and landscapes once dominated by forest are now dominated by other land uses (Wickham and others 2007, 2008). In 16 of the 31 Eastern States, the wildland-urban interface now encompasses more than 25 percent of total land area (Radeloff and others 2005), and one-third of the eastern forest exists within neighborhoods that also contain at least 10 percent agricultural landcover (Riitters 2011).
Riitters, Kurt H.; Coulston, John W. 2013. Fragmentation of eastern United States forest types. In: Potter, Kevin M.; Conkling, Barbara L., eds. 2013. Forest health monitoring: national status, trends, and analysis 2011. Gen. Tech. Rep. SRS-GTR-185. Asheville, NC: USDA-Forest Service, Southern Research Station. 71-77.