The Grand Canyon
A natural gorge 277 miles long, a mile deep, and up to 18 miles wide, the Grand Canyon cuts across the Colorado Plateaus in northeastern Arizona. Cut downward by the Colorado River as the plateaus were uplifted over the last 17 million years of Earth history, its walls expose spectacular rock formations ranging in age from 2 billion to 230 million years old. The canyon, visited by native populations for thousands of years, first entered Europeans’ consciousness in the 1540s, through the writings of conquistador Garcia Lopez de Cardenas. It was mapped by a succession of government-sponsored expeditions during the 1870s: efforts—led by scientist-explorers John Wesley Powell, George Wheeler, and Clarence King—that were consolidated in 1879 into the U. S. Geological Survey.
The expeditions of the late nineteenth century transformed scientists’ understanding of the canyon. Previously seen as an isolated natural wonder, it was reinterpreted as part of a dynamic system of landforms that included the Colorado River, its tributaries and their valleys, and the surrounding plateaus. Expedition geologists such as Grove Karl Gilbert and Charles Dutton explained the canyon as the product of a complex geological history, shaped by wind and water erosion, the uplift of the surrounding land surface, changes in rainfall, and the effects of volcanic eruptions. The Grand Canyon played a key role in establishing the geological doctrine of fluvialsm: the idea that river valleys are formed by the erosive power of the streams moving through them. It was also one of the first environments whose landforms, topography, subsurface geology, rainfall, and other factors were studied and understood dynamically, as elements in an integrated whole.
The Grand Canyon remained isolated and largely wild until the early twentieth century, when human attempts to manage it began. The canyon’s size and cultural significance has made it, ever since, a focal point for debates about the proper stewardship of unique natural wonders.
The first attempt to manage the canyon and surrounding areas came in 1906, when President Theodore Roosevelt signed an act declaring a million acres on the north rim—the entire Kaibab Plateau--the Grand Canyon National Game Preserve. Designed to protect the local population of mule deer, the preserve was biologically isolated by deep side canyons and surrounding deserts. Hunting of mule deer was banned, and (in keeping with then-current game management practices) the native species of predators were systematically killed off by Forest Service hunters. The mule deer population exploded, rising from 3,000 in 1906 to over 100,000 by 1924. Henry Wallace, then Secretary of Agriculture, ordered that the population be reduced to sustainable levels by hunting, but the order met with fierce opposition from conservationists. Time passed without action, the mule deer devoured the available forage, and starvation set in, causing the population to plummet. The case highlighted the limits of conventional thinking about wildlife management, and inspired Aldo Leopold and others to embrace a more holistic, integrative approach that took into account the balance of predator and prey, the significance of native plants, and the effects of seasonal (and larger) natural cycles.
The preserve, the canyon itself, and other surrounding lands were designated a national monument in 1908 and the nation’s 17th national park in 1919. The age of mass tourism at the canyon was already well underway by then, ushered in by a railway line and, soon afterward, paved roads to and along the canyon’s rim. The paved roads led to a boom in car tourism that the National Park Service enthusiastically supported with parking lots, paved roadside overlooks, and motor-court-style lodgings. Cars, like trains, concentrated visitors in a small area where the access route met the rim. Areas beyond the paved roads on the south rim, and all along the north rim, remained largely wild because they were inaccessible to all but the most intrepid tourists. The concentration of so many cars in so small a space—over a 5 million a year by the late 1990s—meant that the portion of the south rim that defined most visitors’ experience of the canyon was increasingly affected by noise, exhaust fumes and visual clutter. Air tours, which began in 1927 and accounted for 118,000 flights a year by the mid-1990s, raised similar concerns about the interior of the canyon. Under the administration of President Bill Clinton in the mid-1990s the Park Service moved to limit air tours, and to phase out automobile access to the rim in favor of shuttle buses and a revived rail service. As with similar proposals for other parks—limits on snowmobiles at Yellowstone, for example—the restrictions were decried as efforts by “environmental elitists” to limit the park access of “ordinary people.”
The damming of the Colorado river and its tributaries was designed to impound water for hydropower, irrigation, and recreation. Inevitably, however, there were side effects. The completion of Hoover Dam, downstream, submerged the lower end of the canyon under Lake Mead in 1941. Upstream, the completion of Glen Canyon Dam in 1963 regularized and sharply reduced the flow of water through the Grand Canyon. The water that did pass the Glen Canyon Dam came from the bottom of newly formed Lake Powell: cold and sediment free. The Colorado, once a warm, sediment-laden river whose flow varied with the seasons (3,000 to 90,000 cubic feet per second), became a cold, clear river that flowed at a steady-but-reduced volume (8,000-20,000 cubic feet per second). River otters, muskrats, and many of the species of fish native to the Colorado have since disappeared from the canyon, along with numerous species of birds, insects, lizards, and frogs. The natural cycle of scouring and rebuilding that shaped sandbars in the river and beaches along its banks has also been interrupted. Invasive non-native plants have taken hold alongside the river, and non-native algae in the river itself, crowding out native species ill-adapted to the new conditions.
The effects of the Glen Canyon Dam, both on the Grand Canyon and on Glen Canyon itself, raised sensitivity to the environmental effects of large dams. This heightened awareness contributed to the defeat, in 1968, of the Marble Canyon and Bridge Canyon Dam projects, which would have further altered the Grand Canyon’s ecosystem. It also led to an effort to approximate the Colorado’s spring flood by releasing a 45,000 cubic feet per second flow of water from the Glen Canyon Dam for 7 days in late March and early April of f 1996. A series of similar releases followed, but their ability to adequately substitute for natural processes remains in doubt. The Glen Canyon Dam has, accordingly, become a focal point of calls to decommission and remove dams whose environmental costs outweigh their human benefits.
-- A. Bowdoin Van Riper
Fradkin, Phillip. A River No More: The Colorado River and the West, 2nd ed. Berkley and Los Angeles: University of California Press, 1996.
Farmer, Jared. Glen Canyon Dammed: Inventing Lake Powell and the Canyon Country. Tucson: University of Arizona Press, 2004.
Goetzmann, William H. Exploration and Empire: The Explorer and the Scientist in the Winning of the American West. New York: Knopf, 1966.
Martin, Russell. A Story that Stands Like a Dam. New York: Holt, 1989.
Pyne, Stephen J. How the Canyon Became Grand: A Short History. New York: Viking, 1998.
Young, Christian C. In The Absence of Predators: Conservation and Controversy on the Kaibab Plateau. Lincoln: University of Nebraska Press, 2002.