The Ecosystem

Grand Canyon National Park is part of an amazingly varied ecosystem responsible for an immense wealth of flora and fauna. But all is not perfect in paradise, and the park is also a continuation of the land around it, which has been affected by human use. The air is compromised by distant industry and not-so-distant automobiles, the Colorado river constricted by dams, and the silence broken by high-flying jets and low-flying sightseeing planes. Theodore Roosevelt's dictum -- to "leave it as it is" -- now seems oversimplified. In the new millennium, the canyon's ecology depends nearly as much on far-reaching public policy as on nature.

Effects of the Glen Canyon Dam -- Some of the most significant changes in the ecology of the Grand Canyon result from the Glen Canyon Dam, which constricts the Colorado River just northeast of Grand Canyon. Finished in 1963, the dam provides large amounts of subsidized hydroelectric power for cities such as Phoenix and recreational opportunities for approximately four million visitors to Lake Powell every year.

In addition to inundating the once majestic Glen Canyon area, the dam has completely altered the biological communities in and around the Colorado River inside Grand Canyon. Water temperatures in the canyon used to fluctuate from near freezing in winter to 80°F (27°C) or warmer in summer. A mere trickle in winter, the river surged during the spring snowmelt to levels five times higher than the largest floods today. Now, penstocks 230 feet below the surface of Lake Powell take in water that varies only slightly from 48°F (9°C) year-round, at a rate that hardly changes. And the water itself has been sanitized. In pre-dam days, the Colorado carried tons of reddish silt that had washed into it from the canyons of the Four Corners area (thus the name "Rio Colorado," Spanish for "red river"). Today, that silt settles to the bottom of the torpid waters of Lake Powell, and the river emerges from the dam as clear as snowmelt.

These changes decimated the canyon's native fish, which had evolved to survive in the extreme temperatures, powerful flows, and heavy silt of the old river. Four of the eight native fish species died off, and one -- the humpback chub -- is breeding only where warmer tributaries enter the Colorado. In their places, rainbow trout, which were introduced below the dam for sport fishing, have flourished. Along the shores, tamarisk and coyote willow choke riverbanks that pre-dam floods once purged of vegetation. This vegetation now is home to a variety of small lizards, mammals, and waterfowl, which, in turn, attract birds of prey such as the peregrine falcon.

Another effect of the dam has been the loss of an estimated 45% of the beaches along the Colorado River. Before the dam was built, the canyon's huge floods lifted sand off the bottom of the river and deposited it in large beaches and sandbars. The post-dam flows are too weak to accomplish this. There's also a shortage of sand: The reservoir captures approximately 95% of the sand that would otherwise come into the canyon from upstream.

In March 1996, the Bureau of Reclamation, the National Park Service, and a group of concerned environmental groups sought to find out whether a man-made flood released from the dam would restore some of the beaches. For 7 days in March and April 1996, the dam unloosed a sustained flow of 45,000 cubic feet per second -- the maximum it could safely release. Although the flood packed only a fraction of the force of pre-dam deluges, it temporarily restored parts of 80 canyon beaches, and most scientists initially deemed the experiment -- known as the Beach Habitat Restoration Flood -- to be a success.

However, the beaches created during the 1996 flood eroded faster than expected -- 85% of them had washed away within 6 months. This has left a fairly bleak prognosis for the beaches: With the dam in place, years can pass before enough sand accumulates for a productive man-made flood.

The Hoover Dam, near Las Vegas, also affects the canyon. The last 35 miles of the Colorado River in the Grand Canyon are submerged in the still waters of Lake Mead, the reservoir above Hoover Dam.

Effects of Air Traffic -- While the dams encroach on the river, airplanes and helicopters encroach on the natural silence. For years, planes and helicopters were free to fly anywhere over the canyon and below the rims. Then, after a collision between sightseeing aircraft killed 25 people in 1986, the FAA established strict flight corridors for the aircraft and forced helicopters and planes to fly at different altitudes.

Although sightseeing flights have long been forbidden over Grand Canyon Village, their droning is still audible at popular destinations, and public opinion supports reductions in noise. In 2000, the FAA implemented a new set of regulations for sightseeing flights over Grand Canyon. These rules froze the maximum number of air-tour flights per year at the number between May 1997 and April 1998, tightened requirements for the reporting of flights, and replaced one meandering flight route in the western canyon with two straighter ones.

Unfortunately, most visitors won't notice any changes. The busiest flight corridors still thrive, and only a small part of the canyon is out of earshot of aircraft noise, which travels an average of 16 miles laterally from aircraft in the eastern canyon and even farther in the west. However, the cap on flights does ensure that, at the very least, the problem shouldn't worsen much in the future.

By keeping the number of flights relatively constant, the FAA made it easier for researchers to monitor the acoustics in the park. The Park Service and Federal Aviation Administration may use this data in the years ahead, when they discuss ways to achieve Congress's goal of restoring "natural quiet" to at least 50% of the park at least 75% of the time by the year 2008.

The Park Service believes this goal can be safely achieved through a combination of smaller flight corridors, quieter aircraft, and fewer (or shorter) flights. But many obstacles loom. For starters, the Park Service and FAA must agree on exactly what Congress meant. They must decide what constitutes "audible" and what is "quiet technology." The safety of air traffic over the canyon cannot be compromised. And, while environmental groups press for quiet, representatives from the area's air tour industry seek to avoid limits on their operations.

Air Quality -- Northern Arizona enjoys some of the best air quality in the country. But it's not perfect, and air pollution does impact the canyon's ecology. In summer, air pollution comes from urban areas in southern California, southern Arizona, Nevada, and northern Mexico. In winter, during periods of calm weather, nearby pollution sources can play a more significant role. Overall, ozone levels in the park have been steadily rising, and visibility has declined.

The federal Clean Air Act mandates that natural visibility eventually be restored to all National Parks and Wilderness Areas by 2065. Seeking to accomplish this at Grand Canyon, the National Park Service regularly takes part in a commission that includes state and Environmental Protection Agency regulators, Native American tribal leaders, industry representatives, and other interested parties.

The commission achieved a major victory in 1999, when scrubbers were installed at the Navajo Generating Station in Page, Arizona. This coal-burning station may have been responsible for as much as half of the canyon's air pollution in winter, according to Park Service estimates.

Yet the problem extends far past obvious polluters in the immediate area. For natural visibility to be restored, pollution sources ranging from automobile emissions in Los Angeles to factories in Mexico must be addressed. WRAP (the Western Regional Air Partnership) targeted at least a few of these distant polluters in 2001, when it proposed a declining cap on sulfur dioxide emissions throughout the western states.

Forest Fires -- Even as National Park Service scientists fret over air quality, they know that more forest fires are needed in the ponderosa pine forest on the canyon rims. Before humans began suppressing forest fires, these areas experienced low-intensity blazes every 7 to 10 years. These fires made the forest healthier by burning excess undergrowth and deadfall, thinning tree stands, and returning nutrients to the soil. After fire suppression began, however, deadfall and excess undergrowth accumulated on the forest floors, and trees grew too close together. With so much "fuel" available, the fires that did occur burned much hotter than before -- hot enough, even, to kill old-growth ponderosas, which tend to be fire-resistant. Once dead, stands of these grand old trees were often supplanted by faster-growing aspen and fir trees.

In the late 1990s, Congress appropriated additional federal funding for land agencies to manage fire for ecological benefits, either through prescribed burns or what the government calls "fire-use fires" -- unplanned blazes that are allowed to burn. The new funds will enable the National Park Service to burn more areas, more often, improving the health of its forests. Taking into account factors such as air quality, weather, location, fire-danger level, and available manpower, Grand Canyon National Park hopes to do prescribed burns on a few thousand acres per year. Of course, fire use is not an exact science, and in May 2000, a prescribed burn known as an "outlet fire" spread faster and farther than expected, blackening over 14,000 acres near Point Imperial on the North Rim and closing parts of the park for weeks.