Southwest USA Photograph by John Morrison   Western North America: Southwestern United States Deserts and Xeric Shrublands   126,000 square miles (326,400 square kilometers) -- slightly larger than New Mexico Relatively Stable/Intact

· A Tilted Saucer
· Special Features
· Did You Know?
· Wild Side
· Cause for Concern
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A Tilted Saucer

You can imagine the Colorado Plateau as an elevated, northward-tilted saucer. Cutting its way down through this terrain is the mighty Colorado River, which has exposed the millions-of-years-old strata and created the natural wonders of the Grand Canyon. The Colorado Plateau is the only area in the United States and Canada where large mountain rivers run through exposed sandstone. The Colorado Plateau has been called the "land of color and canyons."

Special Features

Other impressive geologic features include monoclines and laccoliths. What are they? Monoclines are areas of folded rock layers, while laccoliths are underground rock masses that cause a large dome-like bulge on the surface. These bulges are responsible for many of the mountains of the area. Elevations here range from 5,000 feet (1,500 m) to 13,000 feet (4,000 m), which means that winters are cold and summers are hot. Each year the area receives 10 to 20 inches (25 to 50 cm) of precipitation. This ecoregion has some of the highest mammal diversity found anywhere in the United States and Canada and also has a very high number of endemic plant species.

	This ecoregion is home to 61 of the 131 species of grasshoppers found in Colorado and also is rich in ant and leafhopper species.

Wild Side

The Colorado River provides habitat for the humpback chub, a highly specialized minnow that can handle the river's fast waters and changing temperatures. The chub, along with the bonytail, squawfish, and flannelmouth sucker, have been hurt by dam and water diversion projects. The region's plants are loosely grouped in vegetation zones. The woodland zone is dominated by low-growing forests of pinyon pine and several species of juniper, with grama, sagebrush, and alderleaf cercocarpus (a type of shrub) growing among the trees. The mountain zone of the high plateaus varies depending on location, with species such as ponderosa pine, lodgepole pine, and aspen. The lowest and driest zone is characterized by grasslands, shrubs, sagebrush, cacti, and yucca. Neotropical migratory birds use this habitat for nesting, and the Mexican spotted owl lives here year-round.

Cause for Concern

About 15 percent of the Colorado Plateau is still intact. The areas that have suffered the most are those along rivers and near mineral-rich areas. The mining for coal and uranium and also oil and gas exploration are associated with pollution in this region. Throughout the ecoregion there has been widespread grazing damage that has been followed by the invasion of exotic species such as tamarisk and cheat grass. Other threats include agriculture, dams, and the expansion of urban areas, particularly Albuquerque and Santa Fe, New Mexico. Human impact from off-road vehicle use and the excessive impacts of recreation are concentrated around Moab, Utah. The greatest threat to wildlife on the Colorado Plateau is the destruction of native fish by dams and other types of development.

For more information on this ecoregion, go to the World Wildlife Fund Scientific Report.