Author: John Sowell, Emeritus Professor of Biology, Western State Colorado University, Gunnison, Colorado
The Upper Gunnison Basin is a high-elevation valley situated at the eastern edge of the Colorado Plateau [topographical map]. Rimmed by some of the highest ranges of the southern Rocky Mountains, the only outlet lower than 10,000 feet elevation is to the west where the Gunnison River passes through the Black Canyon. This narrow gorge appears to act as a filter for the movement of lower-elevation species into and out of the basin. Ecologically, the flora and fauna in the Upper Gunnison Basin appear to be depauperate in taxa, and the region has been recognized for its unique biogeographic characteristics.
The biotic communities of the basin include sagebrush-steppe, which is particularly prevalent from 7,500 feet to 9,000 feet elevation. Mixed-conifer forests dominated by Douglas-fir, subalpine forests of primarily Engelmann spruce and subalpine fir, subalpine grasslands, and alpine tundra blanket the surrounding ranges. Aspen occurs across a wide range of elevations forming both serial and persistent stands. Forests of lodgepole pine are common in the northern half of the basin. Notable is the lack of pinyon-juniper woodlands in the basin. Though Rocky Mountain juniper occurs on rocky outcrops at lower elevations, pinyon pine is absent. Fossil pollen, macrofossils, and radiocarbon-dated charcoal found within archaeological features indicate pinyon pine was common in the basin from 8,000 to 3,000 years before present. Similarly, ponderosa pine has a limited distribution in the Upper Gunnison Basin, though archeological excavation of ponderosa pine charcoal suggests it to was once more widespread.
Humans have occupied the Upper Gunnison Basin for nearly 10,000 years. Based on collective radiocarbon dates and the diversity of archaeological features, prehistoric occupation peaked approximately 6,000 years before present when the climate was warmer and moister and pinyon pine woodlands existed within the basin. The impact of these people on the basin's biota is unknown. More recently, the Uncompahgre Utes hunted in the Upper Gunnison Basin in the summer while spending winters at lower elevations. It is possible that the Spanish visited the Upper Gunnison Basin as early as the 1500s and on through the 1700s, but they left no trace of their presence. American trappers, particularly seeking beaver, entered the Upper Gunnison Basin in the early 1800s though the harvest was limited and the fur trade all but ended in 1844.
It was gold and silver that brought prospectors to the Upper Gunnison Basin in the 1860s, and the rush in the 1880s resulted in the rise and fall of numerous mining towns. After the silver panic of 1893, miners turn primarily to coal and later to uranium. While mining is minimal today, the evidence of past exploits dot the basin. Widespread timber harvest supplied lumber and fuel for the pioneers, and extensive clearing circled each settlement. Cattle were introduced in the 1870s and ranching continues today. Cattle subsist on range by summer, and the impacts of grazing are widespread. Riparian habitats of cottonwoods and willows have been greatly altered by the irrigation of hay meadows and cattle usage.
At the headwaters of the Colorado River drainage, the Upper Gunnison Basin is the only major watershed not tapped by metropolitan water concerns to the east. As the water flows westward, it is impounded in several reservoirs including Blue Mesa Lake, the largest body of water in Colorado. Blue Mesa Lake was created in 1965 and submerged 20 miles of river. Blue Mesa Dam is the first of three dams along the Gunnison River which provide water storage for downstream agricultural needs, flood control, electrical power, and recreational opportunities.
Today, over 85% of the Upper Gunnison Basin is federal land managed by the Park Service, Bureau of Land Management, and Forest Service. Seven Forest Service wilderness areas and a Bureau of Land Management primitive area afford protection to diverse high-elevation landscapes within the basin. Curecanti National Recreation Area preserves a fringe of lower-elevation terrain surrounding Blue Mesa Lake. Grazing continues across much of the basin, though range condition has improved since the 1970s, in part through fire management and reduced cattle utilization. Irrigation of stream-side hay fields and cattle usage continue to degrade riparian vegetation at lower elevations. Timber harvest is minimal, and the impact of logging during the mining era has largely been erased. Presently, recreation and tourism is a prevalent land use in the Upper Gunnison Basin.
Click here for a map of current vegetation zones and paleoecological sites in the upper Gunnison Basin.
Late Holocene Environmental Change in the Upper Gunnison Basin, Colorado. The Upper Gunnison Basin is a high elevation (7,500 to 14,000 feet) 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.
Crawford, J.L., S.P. McNulty, J.B. Sowell, and M.D. Morgan. 1998. Changes in aspen communities over 30 years in Gunnison County, Colorado. American Midland Naturalist 140: 197-205.
Emslie, S.D. 1986. Late Pleistocene vertebrates from Gunnison County, Colorado. Journal of Paleontology 60: 170-176.
Emslie, S. and M. Stiger. 1998. Ecology and paleoecology of the upper Gunnison Basin, Colorado. [http://people.uncw.edu/emslies/ugb/]
Fall, P.L. 1985. Holocene dynamics of the subalpine forest in central Colorado. American Association of Stratigraphic Palynologists Contribution Series 16: 31-46.
Fall, P.L. 1997. Timberline fluctuations and late Quaternary paleoclimates in the Southern Rocky Mountains, Colorado. Geological Society of America Bulletin 109: 1306-1320.
Ralph Falsetto, J.Soceka, J. Sowell and A. Stork. 1998. Digital landcover map of the Gunnison Basin. [http://www.western.edu/academics/geology/research/landcover/digital-land-cover-map-of-the-gunnison-basin.html]
Johnston, B.C. 1999. Ecological types of the Upper Gunnison Basin [draft]. Technical Report. USDA Forest Service, Rocky Mountain Region, Lakewood, Colorado. 870 pp.
Jones, B.A. 1984. Radiocarbon dates from the Gunnison Basin, Curecanti National Recreation Area, Colorado. Southwestern Lore 50: 14-22.
Komarkova, V., R.A. Alexander and B.C. Johnston. 1988. Forest vegetation of the Gunnison and parts of the Uncompahgre National Forests: A preliminary habitat type classification. USDA Forest Service General Technical Report RM-163. Rocky Mountain Forest and Range Experiment Station, Fort Collins, Colorado. 65 pp.
Langenheim, J.H. 1962. Vegetation and environmental patterns in the Crested Butte area, Gunnison County, Colorado. Ecoogical Monographs 32: 249-285.
Schauer, A.J., B.K. Wade, and J.B. Sowell. 1998. Persistence of subalpine forest-meadow ecotones in the Gunnison Basin, Colorado. Great Basin Naturalist 58: 273-281.
Stiger, M. 2001. Hunter-gatherer archaeology of the Colorado high
country. University Press of Colorado, Boulder.
Vandenbusche, D. 1980. The Gunnison Country. B & B Printers, Gunnison, Colorado. 472 pp.
Young, J.R. 1999. The Gunnison sage grouse. [http://www.western.edu/faculty/jyoung/gunnison-sage-grouse]