Picking Up The Pieces

The once unbroken forests that once stretched across vast swathes of North America are mostly gone, broken into pieces by cities, roads and farms. Now a new study attempts to quantify fragmented forests in the Eastern United States – and finds that privately-held lands may play a key role in keeping things together.

“Fragmentation is an ever-present threat to forest communities in the eastern United States,” Kurt H. Riitters and John W. Coulston of the U.S. Forest Service and James D. Wickham of the U.S. Environmental Protection Agency write in Forest Ecology and Management. Forests that get broken into little pieces are more vulnerable to invasive species, for instance, and to losing some species. entirely And past large-scale studies showed that fragmentation in the East was “pervasive,” they note, with one finding that just 10% of forest plots were still “intact.” Those studies, however, were relatively coarse-grained, the trio writes.

To get a more fine-grained view, they turned to a combination of satellite images and one-the-ground reports compare fragmentation in 70 forest communities in 31 eastern states. In particular, they looked at conditions in 4.41-hectare plots in a wide range of forest types, ranging from common oak and pine forests, to rarer cypress and cottonwood stands. They also compared fragmentation in publicly- and privately-owned forests.

Overall, about 55% of the approximately 143 million hectares covered by the study had become fragmented by the late 2000s, they report. “The percentage of intact forest ranged from 31% for the elm/ash/cottonwood group to 60% for the maple/beech/birch group,” they note. And within specific forest “communities,” the portion of intact forest ranged from 13% to 78%. Although natural features – such as rivers – sometimes caused fragmentation, the cause was often human development of farms, roads or communities.

“Fragmentation was also higher on privately owned forestland than on public forestland,” they note. “Overall, approximately 62% of public forest area was intact forest, compared to 40% of privately owned forest.” But because about 80% of forests are in private hands, “privately owned forest contributed 2.5 times more intact area than public forest… In other words,” they note, “the total regional supply of intact forest is driven mainly by private land management practices.” David Malakoff | October 30, 2011

Source: Riitters, K., Coulston, J., & Wickham, J. (2012). Fragmentation of forest communities in the eastern United States Forest Ecology and Management, 263, 85-93 DOI: 10.1016/j.foreco.2011.09.022

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