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 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 it does on nature.

Effects of the Glen Canyon Dam

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

In addition to inundating the once majestic Glen Canyon area with water, the dam has altered the biological communities in and around the Colorado River. Water temperatures in the canyon used to fluctuate from near freezing in winter to 80°F (27°C) or warmer in summer. The river, a mere trickle in winter, surged during the spring snowmelt to levels five times higher than the biggest floods today. Now, penstocks 230 feet below Lake Powell's surface take in water that varies only slightly from 48°F (9°C) year-round, at a rate that hardly changes. And the water has been sanitized. In predam 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 Lake Powell's torpid waters, and the river emerges from the dam as clear as snowmelt.

These changes (along with the Hoover Dam's impact and the introduction of new fish species) undermined the canyon's native fish population, which had evolved to survive in extreme temperatures, powerful flows, and heavy silt. 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 predam floods once purged of vegetation. This plant life is home to 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 sand from 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 postdam flows are too weak to accomplish this. There's also a shortage of sand: The reservoir captures about 95% of the sand headed into the canyon from upstream.

In 1996, the Bureau of Reclamation, the National Park Service, and a group of concerned environmental groups sought to find out whether a manmade 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 predam deluges, it did temporarily restore parts of 80 canyon beaches. Most scientists initially deemed the experiment -- known as the Beach Habitat Restoration Flood -- a success.

However, the beaches created during the 1996 flood eroded faster than expected -- 85% of them had washed away within 6 months. Additional experimental flows were performed in 2000, 2004, and 2008 designed to mitigate the erosion.

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 and forced helicopters and planes to fly at different altitudes.

Though sightseeing flights have long been forbidden over Grand Canyon Village, their droning is still audible at popular destinations, and public opinion supports noise reductions. In 2000, the FAA implemented new regulations for sightseeing flights over Grand Canyon: These froze the maximum number of air-tour flights per year at the number between May 1997 and April 1998, tightened requirements for reporting 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. The sounds travel 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 acoustics in the park. The Park Service and FAA may use this data to help achieve Congress's goal of restoring "natural quiet" to at least half of the park during the majority of daylight hours.

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 "quiet technology" is. 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 America's best-quality air. 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; visibility has declined.

The federal Clean Air Act mandates that natural visibility eventually be restored to all national parks and wilderness areas. Seeking to accomplish this goal at the Grand Canyon by 2065, the National Park Service regularly takes part in a commission that includes state and federal EPA regulators, Native American tribal leaders, industry representatives, and other interested parties.

Efforts to improve air quality passed successfully in 1999 when scrubbers (air-pollution control devices) 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.

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. Utah, Arizona, Wyoming, and New Mexico are the four participating states and are meeting the declining cap and successfully implementing the recommendations.

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, flammable material again 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. These grand old trees, once gone, can not be replaced for centuries and changes in climate may preclude them from ever returning.

Today, fire suppression is no longer an automatic response. Land management agencies try to manage fire for ecological benefits. New policies enable the National Park Service to burn more areas more often, improving the forest health. Taking into account factors such as air quality, weather, location, fire-danger level, and available manpower, Grand Canyon National Park hopes to carry out prescribed burns on a few thousand acres per year. Prescribed fires are ignited and monitored under scientific conditions in order to achieve specific objectives, such as reducing forest fuels. Fires caused by lighting may be allowed to burn within an identified, undeveloped area for the same purpose as prescribed fires. Of course, fire use is not an exact science; in May 2000, a prescribed burn named the Outlet Fire spread faster and farther than expected, blackening more than 14,000 acres near Point Imperial on the North Rim, and closing parts of the park for weeks. Another forest service fire in 2006, called the Warm Fire, jumped over Highway 67 and scorched an area south of Jacob's Lake.

In the face of climate change, we remain unsure about the impact of stand-replacing fires. Our models still aren't effective at predicting future precipitation, although longer droughts followed by heavy downpours seem to be the new pattern.

Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.