Biota of the Colorado Plateau

Wellsville Mountains, Utah. Photo © 1999 Ray Wheeler

From sparse desert communities growing in the region’s rugged canyons to alpine tundra found atop the highest peaks, the biota of the Colorado Plateau is exceptionally diverse. This diversity can be attributed to the region’s varied topography and its geographic position in the western United States. The Colorado Plateau is sandwiched between the Great Basin to the west, an arid region of alkaline basins and faulted mountain ranges, and the Rocky Mountains to the east, a lusher landscape of high peaks and rich forests. The region’s flora and fauna thus has elements of each of these provinces as well as a significant number of endemic species that have evolved in areas of relative isolation atop the Plateau.

Elevation largely determines what type of biotic communities one may find in a given location, as temperatures generally decrease and precipitation increases as one moves upward. At 4000 feet in Canyonlands National Park one may be in a desert shrub community dominated by blackbrush or shadscale, while just to the east in the La Sal Mountains, but more importantly 5000 feet higher, rich grass-forb meadows and forests of quaking aspen dominate the landscape.

There are numerous other factors–recent, historical and ancient–that have affected the distribution of plant and animal species on the Colorado Plateau. Short and long-term climate change has played a large role in the development of the region's biota. In the last two millenia human activities have altered the region's environment. In the Four Corners area, the prehistoric Anasazi were so populous by the end of the 12th century that they must have had a significant impact on the landscape. Historically, among the Plateau's forests, the suppression of wildfire coupled with widespread grazing and intensive logging has led to many unforeseen changes, including changes in the composition and structure of forests as well as the spread of exotic species. Dam building and excessive pumping of groundwater have damaged many riparian ecosystems, which are critical to this dry region’s plant and animal life. Though ongoing natural processes such as succession and climate change continue to alter the region's biota, the rapid changes seen today due to human activities are unprecedented in their impacts on the biota of the Colorado Plateau.

Research:

Packrat Midden Research in the Grand Canyon. On the Colorado Plateau the ice age (Pleistocene) vegetation of the Grand Canyon has been determined through the analysis of plant fossils preserved in caves and fossil packrat middens.  Large changes occurred as the most recent ice age ended and the Holocene era began. Adapted by Kenneth L. Cole from his journal article.

Paleobotany and Paleoclimate of the Southern Colorado Plateau. The biota of the Colorado Plateau during the middle (50,000-27,500 B.P.) and late (27,500-14,000 B.P.) Wisconsin time periods was dramatically different from that seen today. Differences were primarily a result of major climate changes associated with the last major glacial period. This site examines the environment of the southern plateau during this time. Adapted by R. Scott Anderson from his journal article.

Native Americans and the Environment. A comprehensive survey of twentieth century environmental issues facing Native Americans on the Colorado Plateau and throughout the Southwest, including discussions of agriculture, logging, mining, grazing, water rights, and tourism. Adapted from a published journal article by David Rich Lewis.

Late Holocene Environmental Change in the Upper Gunnison Basin, Colorado. The Upper Gunnison Basin is a high elevation (3100 to 3600 m) region on the edge of the Colorado Plateau in southwestern Colorado. Its unusual ecological characteristics include an absence of plant and animal taxa that should occur here. Fossil and archaeological evidence indicates that many of the missing species existed in the Basin during the late Pleistocene to middle Holocene. Authored by Steve Emslie.

Fire-Southern Oscillation Relations in the Southwestern United States. A close linkage between fire and climate could diminish the importance of local processes in the long-term dynamics of fire-prone ecosystems. The structure and diversity of communities regulated by fire may have nonequilibrial properties associated with variations in global climate. Successful prediction of vegetation change hinges on a better understanding of climatically driven disturbance regimes and the relative contributions of regional versus local processes to community dynamics. Adapted from a journal article by Thomas W. Swetnam and Julio L. Betancourt.

Changed Southwestern Forests: Resource effects and management remedies. Over 150 years of occupancy by northern Europeans has markedly changed vegetative conditions in the Southwest. Less fire due to grazing and fire suppression triggered a shift to forests with very high tree densities, which in turn contributed to destructive forest fires. Options to deal with these changes include prescribed fire, thinning and timber harvest to mimic natural disturbances and conditions. However, there are barriers to implementing these activities on a scale large enough to have a significant benefit. Adapted from a published journal article by Marlin Johnson.

Where have all the grasslands gone? Numerous ecological studies across the Southwest have documented the decline in herbaceous vegetation (grasses and non-woody flowering plants) while forests thicken and brush invades. Documenting the changes in the Jemez Mountains of northern New Mexico, ecologist Craig Allen considers the evidence that these patterns are tied to changes in land use history, primarily livestock grazing and fire suppression.