Utah-Wyoming Rocky Mountains Ecoregion

Description & Physiography

The Utah-Wyoming Rocky Mountains Ecoregion includes the mountains four states, and includes the Greater Yellowstone Ecosystem (GYE), considered one of the last intact temperate ecosystems on Earth, and the farthest south in North America. Yellowstone is an extraordinary place containing the greatest concentration of geysers, hot springs, and other thermal features in the world. Not surprisingly it is a World Heritage Site.


As a high mountainous region in the interior West more than 800 miles from the moderating effects of the Pacific Ocean, the climate of the ecoregion is generally characterized as cold continental. Winters are long and summers short. Snow cover at 7,000 feet in Yellowstone Park typically lies upon the ground for an average of 213 days and lasts another 29 days for every 1000 feet of elevation gain.

Climatic conditions interacting with topographical features affect many aspects of the ecoregion’s biological heritage. The greater acreage and abundance of aspen in the southern part of the ecosystem is a consequence of greater summer rainfall, while the abundance of big game that winter in the Gardiner, Montana area is a consequence of low precipitation created by rain shadow effects. In general, the western part of the ecosystem in Idaho and adjacent parts of Montana and Wyoming receives the greatest annual precipitation. This is readily apparent to anyone who travels extensively around the region, with places like the south slope of the Centennial Range, the west slope of the Tetons, and other mountains in the western and southwestern parts of the ecosystem appearing extremely lush. For example, the southeast corner of Yellowstone National Park often receives more than 80 inches of annual precipitation.

Plants & Animals

Yellowstone Park is the only large area in the coterminous United States that has never been farmed, ranched, or logged. Hence, the area is home to all the native species that existed at the time when the first Europeans explored the region except for the passenger pigeon. The GYE contains a minimum of 337 species of mammals, birds, and fish, and more than 12,000 species of insects. It is home to one of the last remaining grizzly bear populations in the lower 48 states and the last continuously wild buffalo herd in the country. It has the greatest concentration of elk in the world. And its cold water fisheries are world famous.

The UWRM is dominated by extremes in climate that include long periods of cold, heavy snow, and often-arid summer conditions. Depending upon elevation, these environmental constraints limit the number of plants that can adapt to these conditions. The lowest elevations tend to be treeless except along riparian zones and dominated by grass-shrub communities. A broad belt of forest is found throughout the middle elevations, with alpine tundra found at the highest

parts of the mountain uplifts. Depending on the location, either ponderosa pine, Douglas-fir, or Rocky Mountain juniper is the first tree species that typically delineates the lower tree line. As one moves higher in elevation, Douglas-fir is intermixed with aspen. Aspen is most abundant in the southern end of the ecosystem and relatively uncommon in the northern reaches of the area, most likely as a consequence of greater summer precipitation that characterizes the southern mountains of the ecosystem

Humans & History

Numerous threats exist to the long-term biological integrity of this region. Human activities include logging, mining, oil and gas development, livestock production, industrial tourism, and a burgeoning population growth with attendant issues of sprawl and development. Not all of these threats affect every acre of the ecoregion, but their cumulative influences are leading to significant biological impoverishment and functional disruption. Fortunately for the biological

future of this region, sustaining the ecoregion’s biological capital is becoming increasingly recognized as key to sustaining its economic health and human communities, as well.


In recent years many biologists have recognized that most protected landscapes like national parks are in and of themselves, too small to maintain fully functioning ecological processes and representative populations of all native species. Thus, the idea of expanded, landscape-scale protection strategies has evolved and has been frequently discussed for the GYE.

Perhaps more importantly, such ecosystem-scale ecological processes as wildfire and predation by large predators such as the wolf still function over much of the landscape. In partial recognition of its exceptional biological, geological, and historical value, much of the Greater Yellowstone Ecosystem is protected from unbridled development with key areas like Yellowstone National Park and Grand Teton National Park as core components of this ecosystem.

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Links to Completed Ecoregional Assessments

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