Roads, Highways, and Ecosystems
John Stilgoe, Harvard University
©National Humanities Center
(part 4 of 6)
By the late 1930s, when the low-pressure tire replaced the high-pressure ones so likely to blow out, the expression going like sixty entered American vernacular
English as meaning going so fast that control began to lessen and lessen. In 1941, when the Pennsylvania Turnpike
opened as one of the first limited-access divided highways that presaged the
post-World War II interstate highway system, motorists discovered it lacked any
speed limit at all. Along some
stretches the average speed hit ninety miles an hour, and half-wondering,
half-terrified motorists gripped their steering wheels and marveled at speeds
undreamed of twenty years earlier. Once
the United States entered the war, gasoline shortages reduced speeds
dramatically, but long after the federal government built the Military and
Interstate Highway System—to use its real name, which designates it as a weapon
and so able to be built by a Congress forbidden by the Constitution to build
highways—American motorists remembered the thrilling years of going far faster
half-terrified motorists gripped their steering wheels and marveled at speeds undreamed of twenty years earlier."
|Florida Highway 25 under construction|
|Florida State Archives|
Any road rewards sustained scrutiny. Roads are so taken
for granted that very few Americans look at them closely. But an accurate look reveals the crown so carefully engineered into the asphalt pavement, the complex system of storm
drains—and ditches—that carries away rain water, the super-elevated curves that carry automobiles around bends at high speed, the wide shoulders that let motorists pull off pavement without driving immediately into ditches, all the
details in which highway engineers take such well-deserved pride.
|Highway 30, New York, with fine grading, wide shoulders, drainage fields, and grassing for erosion control
details in which highway|
engineers take such well-deserved pride."
But look again. Every road is a sort of ecosystem that ecologists are only just now starting to study. Non-porous pavement causes rainfall to collect at its edges, if only momentarily. So along most roads across much of the
western United States, say west of the 98th meridian of longitude,
the edge of the pavement is bordered by a ribbon of plants that need slightly
more annual rainfall than do the plants only three or four feet away. Quite often the ribbon plants are taller and
greener than ones growing a few feet distant,
and the plants shelter wild animals
waiting to cross what they sense, correctly, is a barrier. For reptiles, especially at night in cool
weather, the blacktop is a warm place to rest, and often a fatal one. For many mammals, it is a zone to be crossed
at speed, but not only because vehicles present a threat: the road offers nowhere to hide from hawks and other raptors. But predatory birds, and carrion feeders too, risk annihilation, for they are easily struck by vehicles, especially at dusk when headlights blind and disorient them. Yet for all that
the road is a barrier, its edges are also animal highways. This last is incredibly important, but still
very little understood.
Consider the typical interstate highway interchange. What lives at the center of the circular zones wholly surrounded by highways and on- and off-ramps? Sometimes essentially grass, routinely mowed. But sometimes all sorts of vegetation and the animals that hide in the wetlands and woods so close to roads pedestrians never cross.
|D.C.||National Archives|| |
Or think about the shoulders of interstate highways. What sorts of animals move parallel to the pavement? Are they safe from some sorts of predators? Do they use the shoulders only as routes or do they live between fence and pavement, in a ribbon of half-cared-for vegetation never walked by humans and indeed almost invisible to humans driving at high speed? A traffic tie-up proves useful to the thoughtful, well-educated motorist who looks acutely at the edge of the highway, a strip that is like the margin on the page
of a book. It is the edge neither of typeset words nor paper. It is truly a twentieth-century and twenty-first-century ecosystem.
|Interstate 5, near Los Angeles, California, 1975||National Archives|
|"the edge of the highway . . . is truly|
a twentieth-century and twenty-first-century ecosystem."
Moreover, it is a prototype of other ecosystems, especially business ones. Paved roads transformed American towns and cities by allowing businesses to spread along the automobile traffic. Just as the pavement increases rainfall
runoff and enables certain plants to prosper along it, so traffic causes businesses to prosper along all but limited access highways. Put up a building and a sign, and some
motorists will pull off the public pavement into the private parking lot, get out, and buy. Railroads concentrate
businesses, for passenger trains stop only at specific locations. Highways cause business to spread out, to move to suburbs, to the edge of town, to form commercial strips dependent on motorists pulling to the edge of the pavement—just as rainfall runoff does.
|National Archives|| |
TeacherServe Home Page
National Humanities Center
7 Alexander Drive, P.O. Box 12256
Research Triangle Park, North Carolina 27709
Phone: (919) 549-0661 Fax: (919) 990-8535
Revised: July 2001