"Do nothing to mar its grandeur for the ages have been at work upon it and man cannot improve it. Keep it for your children, your children's children, and all who come after you..." - Theodore Roosevelt
One of the most spectacular natural features in North America and perhaps the world, the Grand Canyon of the Colorado River extends for hundreds of miles across a portion of the southwestern Colorado Plateau. Here the river winds it way through a network of huge amphitheatres, spectacular tributary canyons, and isolated plateaus and mesas. The vertical drop to the river from the vast plateaus surrounding the canyon is more than 2000 meters, spanning more life zones than exist within any other U.S. national park.
Atop the North Rim, which is an average 600 meters greater in elevation than the South Rim, are lush forests of spruce, aspen, pine, and fir. The lower South Rim is drier, warmer and more open and includes forests of ponderosa pine and Gambel oak mixed with pinyon pine and Utah juniper woodlands. Below the rim much of the vegetation in the inner canyon is semi-arid scrub dominated by drought-resistant shrubs and cacti, while the Colorado's riparian corridor includes thickets of willow and introduced tamarisk. The Grand Canyon's ecological and geological complexity and its interesting human history make it a major scientific research site on the Colorado Plateau.
Certain vegetation communities are unique to the Grand Canyon, with plants that do not normally form associations growing in close proximity. Vegetation gradients do not follow strict elevational zones; instead, plants respond to the canyon's unusual climatic factors, such as air recirculation within the canyon's steep walls and microclimatic variations in precipitation and soil characteristics.
There has been a great deal of research done on the paleoecology and paleoclimate of the canyon, as determined by packrat midden analysis and other fossil studies. For example, Kenneth Cole's midden studies have revealed that not only are current life zones 800-1000 meters lower than they were 12,000 years ago, but that species composition and associations have changed over time.
Grand Canyon National Park is home to a number of threatened or endangered species. Several native Colorado River fish populations have declined as a result of the dramatic changes in water volume, temperature and sediment load of the Colorado River since the completion of Glen Canyon Dam upstream in 1963. These include the Colorado squawfish, humpback chub, and bonytail chub. The park is also home to several species of endangered birds and a number of endangered plants. During the late Pleistocene, several now-extinct large mammals were common in the canyon, including the Shasta ground sloth, the American camel and the American horse.
Prehistoric Human Occupation
Humans have lived in or near the Grand Canyon for at least 4000 years. Archaic peoples occupied the caves and rockshelters of the canyon walls, leaving behind rock shrines and hundreds of split twig figurines that were probably used in ceremonies or as hunting talismans. By the early centuries A.D., several cultures lived within and around the canyon. Based on the archaeological record, the Kayenta Anasazi were the largest and most extensive presence, but the Cohonina people were also present on the South Rim. Permanent farming settlements were established on the South Rim around 700 A.D. and on the North Rim by 900 A.D.; these communities were successful for several hundred years. The well-preserved Tusayan ruins on the South Rim provide modern visitors a glimpse of the lifestyle of these early farmers. Pueblo peoples moved into the canyon and began farming arable patches of land about 1050 A.D. This was a relatively short-lived venture since the climate started to become drier and warmer about this time. By 1150, all of the settlements in and around the canyon had been abandoned, probably at least in part due to prolonged periods of drought.
The only exception to this exodus were several sites near Havasu Creek, an area within the canyon with fertile land and a reliable water source, which remain occupied by the Havasupai Indians today. The Havasupai are the only tribe still living in the canyon today, while their close relatives the Hualapai live along the southern rim of the canyon west of the national park. Navajo peoples live in the Navajo Nation just east of the park, but are only known to have occupied the canyon when a group of them fled from the relocation campaign of Kit Carson in 1863 in the Wupatki Basin and other southern regions. The Southern Paiute Indians occupy land north of the Colorado River along the Arizona Strip and have traditionally used the canyon for hundreds of years.