I suspect that many of us have visited a natural area from our childhood only to find it paved over by a shopping center or converted to suburban development. Elected officials call this economic progress and applaud the added tax revenue. Ecologists call it sprawl.
Just how much land is under human domination in the United States? Satellite photographs show that 2.7% of the land is illuminated at night—a good measure of human occupation. And, agricultural occupy about 21% of the U.S.
The length of roads in the same area exceeds 2.6 million miles, so no one in the U.S. is ever more than 21 miles from a road, and most of us find ourselves within 1 mile of a road.
These statistics are relevant to concerns about the fragmentation of natural lands in the U.S. and worldwide. Fragmentation occurs when a road crosses a contiguous natural area, producing two units separate from one another. Fragmentation reduces the quality of the habitat for large predatory animals and increases the habitat and often the invasion of species that prefer roadside and edge habitat. In one recent study in Thailand, fragmentation did not lead to an immediate extinction of species, but all native mammals disappeared from the resulting fragments over a 25-year period.
Fragmentation leads to subtle and insidious impacts on natural areas that remain for biodiversity. Land planning should consider these impacts of fragmentation, or there may be no woods for us to stop by and enjoy.
**********
.
Web Links
Photo, taken on December 6, 2009, courtesy of Nicholas A. Tonelli via Flickr.
Earth Wise is a production of WAMC Northeast Public Radio. Support for Earth Wise comes from the Cary Institute of Ecosystem Studies in Millbrook, NY.