Ecosystems of the Rocky Mountains
High Peaks and Deep Canyons
The Rocky Mountains were formed, and are influenced today, by continuing interrelated processes of geology, climate, fire, and more recently, human activity.
The Rocky Mountains are young, geologically speaking — only about 65 million years old — yet there is evidence of every geological process known to build mountains. Multiple events uplifted, folded, carved, erupted, and eroded the landscape over millions of years.
The most recent major event occurred between 70 million and 40 million years ago. Plates of the earth's crust collided repeatedly, folding and piling on top of each other. This uplift drained an ancient sea that once occupied the center of what is now North America, and formed what we know today as the Rocky Mountains. Volcanoes, glaciers, and erosion have further defined and reshaped these mountains and valleys; signs of glacial and volcanic activity are evident throughout the region.
|Evidence of glacial activity abounds. Here, an alpine lake fills a glacially carved cirque (steep–sided semicircular hollow) in Payette National Forest, Idaho. Photo by T. Demetriades–Josophene, U.S. Forest Service.|
Current geologic activity is most obvious in Yellowstone National Park, which is underlain by molten rock that fuels its famous geysers. But the process of mountain shaping can be subtle, too. Wind, rivers, and streams erode mountains, while glaciers continuously gouge and scrape the rock over which they move. Water seeps into rocks, breaking them as it freezes and expands. Mountains may look static, but looks can be deceiving.
The Way West
The shape of the Rocky Mountains determined the routes of American Indians and later, early settlers, who sought the easiest way through the rugged terrain. This was through mountain passes, the same routes as many highways traverse today.
Historically, the easiest pass was South Pass in Wyoming. South Pass is a gently sloping rise that crosses the Continental Divide in the Wyoming Basin, a large upland plateau. An estimated half million pioneers bound mostly for Oregon, California, and Utah traveled through this pass.
Passes in the southern Rockies are steeper and more hazardous. And to the north, explorers Lewis and Clark ventured over treacherous Lolo Pass, an ancient Indian route crossing the rugged Bitterroot Mountains along the Idaho-Montana border.
Extreme wind and cold characterize the forest tundra transition area between the dense subalpine forest and the treeless alpine tundra. Here, stunted trees grow in isolated clumps. "Flag trees" indicate the prevailing wind direction, with branches surviving only on their leeward sides. On the coldest and windiest sites, trees abandon their erect growth form and become shrubby mats. Limber and bristlecone pine trees grow into twisted forms as they cling to rocky knobs and ridges. Limber pines' flexible branches bend without breaking. The tree's scientific name, Pinus flexilis, refers to this adaptation. Bristlecone pines grow a limited number of new needles each year; each needle can perform photosynthesis for 10 to 15 years.
|The Gunnison River in Colorado carved the Gunnison Gorge over millions of years. Managed by the BLM and the National Park Service, this is a popular recreation area and also home to bighorn sheep, elk, deer, and bald eagles.|
Key alpine plant adaptations are low-growth forms and small sizes. Many alpine plants also have extensive root systems to tap scarce moisture and nutrients, as well as to stay firmly anchored in windy conditions. Dense coverings of hairs protect sensitive leaves, shoots, and flowers from the drying effects of the constant wind.
Only a few animals can withstand the harsh winters of the alpine zone. The yellow-bellied marmot is an alpine rodent that hibernates through the winter, while the pika, a small, round relative of the rabbit, stays active, living off stored grasses and herbs. White-tailed ptarmigan have densely feathered feet that function like snowshoes. The chickenlike bird changes plumage from summer dark to winter white. Weasels undergo a similar change in color.
|The low-growing dwarf clover is adapted to living at high altitudes.|
Adapting to Fire
Fire is a natural part of forest ecosystems in the Rocky Mountains and many plants have adapted to fire.
|Students at the McCall Outdoor Science School (MOSS) in Idaho smell the sweet scent of the ponderosa pine in Ponderosa State Park. The tree is also known as yellow pine for the distinctive hue of mature trees, and by children as the "puzzle tree" for its bark structure, which resembles puzzle pieces. Photo by University of Idaho, MOSS.|
Ponderosa pine forests depend on fire to create open stands that let in sunlight. Low-intensity fires clear the forest floor and assist germination of ponderosa pine seeds. Seedlings thrive in the sunlit forest. The ponderosa pine's thick bark and deep roots protect it from fire and the trees' large buds are protected by insulating scales. In addition, mature trees tend to "self-prune," losing their lower branches. This keeps a surface fire from becoming a "crown" fire, one that advances from treetop to treetop.
Lodgepole pine trees produce both closed and open cones. Closed (serotinous) cones remain on the tree and are sealed with heavy resin until the heat from a high-intensity fire opens them and releases the seeds by the millions.
A Place to Roam
Mountains often provide the only places where large predators can find unfragmented habitat to roam and hunt. Wolves and grizzly bears, for example, historically existed in a variety of ecosystems, but today exist in the Rocky Mountain region mostly in small populations in or near parks and wilderness areas. Both species are at the top of the food chain, helping to control the populations of other animals such as deer and elk.
|Canada lynx. The southern part of its range extends into the Rocky Mountains. Photo by Milo Burcham, U.S. Forest Service.|
The presence of top predators within an ecosystem can benefit many species of plants and animals. As part of an effort to restore the Greater Yellowstone Ecosystem, wolves were reintroduced to the Rocky Mountains in 1995. As their numbers have increased, the behavior of elk has changed.
To protect themselves, the elk now move around more frequently. This, coupled with a slight decrease in elk populations, has relieved pressure on the riparian plants that elk eat. Trees, such as willows, cottonwoods, and even aspens are now flourishing, providing improved habitat for smaller animals and birds. A greater density and diversity of plants also assists in filtering water and combating erosion.
|Elk not only need large habitat areas, but also require habitat corridors that connect their summer and winter ranges. Photo by Betsy Wooster, BLM.|
The Canada lynx is one of several wildcat species found in the Rocky Mountains. This predator follows a natural 7–10 year population cycle of "boom and bust" tied to the population of its favorite food, the snowshoe hare.
The Rocky Mountains are managed by a variety of public agencies and private landowners. This public-private "checkerboard" ownership pattern evolved during the West's settlement, which started in the fertile mountain valleys. Much of the high mountain land was eventually set aside as National Forests and National Parks, while odd-numbered sections of land were given to the railroads to encourage construction of rail and telegraph lines. Although much of the Rocky Mountain area has been consolidated into manageable blocks of public or private land, the West's distinctive checkerboard ownership pattern still exists in some areas today. Land that was neither privately settled nor designated as parks or forests was called "public land." Today BLM manages this public land for multiple uses (such as outdoor recreation and oil and gas leasing) while protecting the natural, historical, and other resources of these lands.
A major challenge for land managers is to ensure suitable habitat for large and migratory wildlife species. Public lands generally provide the largest habitat blocks, but wildlife do not necessarily stay within these boundaries. For example, the reintroduced wolves (previously mentioned) now number some 300. They sometimes stray onto private lands and prey on livestock. Defenders of Wildlife, a non-governmental organization, reimburses ranchers for their losses, and the U.S. Fish and Wildlife Service works with other agencies and groups to address problems involving wolves. But the presence of wolves remains controversial.
Grizzly bears also need large, remote habitat blocks. Their numbers were reduced to just several hundred in the continental United States during the last century, but have increased to an estimated 1,200 since federal protection was granted in 1975. Still numerous in Canada and Alaska, grizzly bears in the lower 48 states are concentrated in the Yellowstone and Glacier National Park/Bob Marshall Wilderness areas of Wyoming and Montana. Lack of suitable habitat has been a major limiting factor, but in some areas, grizzly bear populations are expanding with better habitat management and greater public support.
A Growing Thirst for Water
Most large cities are located at the foot of the mountains, with the largest population centers along the Front Range on the eastern side of the mountains. As the area's population grows, so does the need for water, much of which comes from mountain streams and rivers. The Denver metropolitan region gets much of its water through extensive transmountain diversions. These diversions use reservoirs, underground tunnels, and ditches to move water from the wetter western side of the mountains to the drier eastern side, where four out of five Coloradans live. As a result, some counties on the west side lose up to 65 percent of their streamflow.
Living With Fire
New homes in or adjacent to wildlands (undeveloped areas) create special challenges for land managers. Current federal policy seeks to reduce hazardous fuels that feed wildland fires. Millions of hectares of western forests contain high accumulations of flammable fuels, including "ladder fuels"—small trees and brush that carry surface fires up into tree crowns. To deal with hot crown fires, which pose risks to homes and communities, federal agencies are using thinning and prescribed (controlled) fires to reduce fire fuels. These fuel-reduction techniques help protect not only homes, but also power grids, drinking water, critical habitat, soils, and air quality.
Hundreds of nonnative invasive plant species are affecting the economy and ecology of the Rocky Mountains. European cheatgrass has invaded significant portions of the region. Cheatgrass is highly flammable and sprouts quickly after a fire, increasing fire frequencies from every 60 years to every 2–4 years in some areas. Mountain shrub habitat is affected by invasive plants such as leafy spurge and a number of knapweed species. Some wetlands and streamsides at middle to lower elevations are covered with purple loosestrife, an invasive ornamental plant that crowds out the native wetland plants. This alteration of woodland and wetland habitat by nonnative invasive plants is believed to be a contributing factor in the general population decline of woodland bird species that spend the summer in the Rockies. Federal, state, county, and local land managers, and landowners, are mounting aggressive campaigns to stop the spread of these invasives into uninfested areas.
Residential development is on the increase throughout the Rocky Mountains. Several key factors are spurring the West's growing population, including new jobs in recreation and energy development, new technology that allows workers to live almost anywhere, and an influx of retirees. As more private land is developed, public land becomes even more important in ensuring open space for people and for wildlife.
The Greater Yellowstone Ecosystem is an example. At 7.3 million hectares, it is the largest intact temperate ecosystem in the world, containing two national parks, seven national forests, and 12 wilderness areas, as well as private land, much of it under intense development pressure.
Here, large private ranches and farms adjoining public land provide much-needed open space, as well as edge habitat (the zone between two different types of habitat), and transitional zones between wilderness and inhabited areas. But many of these private properties are being subdivided into new residential developments, bringing cultivated lawns, pets, and other impacts to wildlife and water quality.
Partnerships are Key
Some creative partnerships have emerged to slow this loss of open space. The Green River Valley Land Trust in Wyoming encourages ranchers to place conservation easements on their property. A conservation easement limits development to protect certain resources while the landowner retains ownership.
|High in the Rocky Mountains near Gunnison, Colorado, students from Western State College are studying the winter habitat of the Gunnison sage-grouse. Here, students are measuring sagebrush density, height, and percentage of leaf cover. Such research will help land managers plan for the birds' winter habitat needs in an area where development and associated activities are increasingly contributing to habitat loss. The Gunnison sage-grouse currently occupies only about 10 percent of the potential habitat available to it when settlers of European descent first began arriving in the West. Pictured are students John Stanek, Matt Vasquez, and Mary Oswald. Photo by Jessica Young, Ph.D., Western State College of Colorado.|
Along the South Fork and Henry's Fork of the Snake River, proposed residential and resort developments threaten to fragment the river corridor habitat and diminish recreational opportunities by blocking public access. The BLM is working with partners to protect portions of the river corridor and public access to it. One recent conservation easement is preserving traditional land uses where a 60-lot subdivision, nine-hole golf course, and resort were proposed.
Because so many issues cut across jurisdictional boundaries, people are joining forces to tackle tough management challenges. The Blackfoot Challenge in western Montana, for example, involves 30 active partners, including private landowners, federal and state land managers, and local businesses. They have worked to restore and protect the Blackfoot River watershed in Montana through such efforts as planting native grasses, removing livestock feedlots from streamsides, and securing conservation easements.
But a primary goal is to protect the rural lifestyle of the people who live in the area by keeping large-scale development at bay. Toward this end, the partnership provides tours and workshops on rural values, sustainable agriculture, and alternative income sources such as ecotourism and guest ranching.
|The BLM worked with The Nature Conservancy to acquire a conservation easement to protect Fisher Bottom on the South Fork of the Snake River, which flows west from the Rockies through one of the most diverse ecosystems in Idaho. Photo by Karen Rice, BLM.|
|Blackfoot River is born high on the Continental Divide and flows more than 200 km through several ecosystems in Montana. The area encompasses some of the most productive fish and wildlife habitat in the northern Rocky Mountains. Photo by Lee Walsh, BLM.|
Rocky Mountain Tourism
With their scenic views, abundant water, substantial snow, and diversity of wildlife, the Rocky Mountains offer a variety of outdoor recreation opportunities, such as skiing, hiking, white-water rafting, fishing, and all-terrain-vehicle (ATV) riding.The popularity of the Rocky Mountains requires land managers to enhance recreational and visitor services while raising public awareness about responsible ways to recreate on the public lands. The effects from such recreation are considerable. For example, food and trash left by visitors attract bears and other wildlife, which often become accustomed to humans. When hiking trails become crowded, some people may create their own trails and shortcuts. This can damage plants and compact the soil. Compacted soils do not absorb water, leading to erosion and the formation of gullies. Along streams, vehicle tires can damage fragile riparian and aquatic ecosystems or spread seeds of invasive plants to new areas. In response, land managers are working with a variety of recreation groups to implement education and outreach campaigns to reduce such impacts. These cooperative efforts involve local rider groups whose members help the government monitor vehicle activity on public land.
In fulfilling their multiple-use mission, BLM land managers seek to offer the widest array of recreational opportunities while minimizing impacts. Sometimes innovative approaches are necessary. For example, some river managers use a lottery system to keep river raft and boat traffic manageable during summer months. To maintain popular recreation sites and stay within budget, BLM sometimes collects special recreation fees. In addition, thousands of volunteers work in exchange for free campground sites and annual passes. Programs such as "Leave No Trace" and "Tread Lightly!" teach recreationists how to enjoy and respect the outdoors, fostering a personal outdoor ethic.
Going Underground: Mining and Energy Development
The Rocky Mountains contain valuable minerals and energy resources that contribute to America's economy, energy independence, and quality of life. Sources under the jurisdiction of the Interior Department, including BLM-managed lands, account for more than 30 percent of domestic energy production.
Many Rocky Mountain towns, such as Silverton, Colorado, and Butte, Montana, owe their beginnings to mining. The discovery of gold and silver attracted thousands of miners in the 1800s and successful prospectors obtained title to their claims through the federal government. Lead, zinc, and copper later spurred even more development, and today, copper, trona (soda ash), and coal are among the resources extracted from the Rocky Mountains.
|Bikers ride along the Gold Belt Tour National Scenic Byway in Colorado, past one of many historic mine sites. Photo by Ruth Zirkle.|
In a previous era, mining often damaged the landscape. Today's mining is carried out with better technology and under laws and regulations aimed at ensuring environmental protection.
Rich Natural Gas Fields
While most U.S. oil and natural gas production takes place offshore, public lands in the West supply a significant amount of natural gas, a clean-burning fossil fuel mostly made up of methane. An oil and gas inventory by the Interior and Energy Departments in 2003 found that federal lands in five key western geologic basins contain nearly 140 trillion cubic feet of natural gas, enough to supply the 56 million homes that use natural gas for the next 30 years.
One area of interest for natural gas development is the Rocky Mountain Front. Here, the geological history set up unique conditions for the creation of rich supplies of natural gas. The key is an ancient seabed that provided organic debris as source material. Deep underground, heat turned this organic debris into oil and gas. Geologic movements of rock over time created underground spaces (reservoirs) that stored the oil and gas, with barriers on top that trapped them. As a result, experts believe there is a large reserve of natural gas trapped along the eastern mountain front in Wyoming and Montana. New technology makes extraction more feasible.
Balancing Multiple Uses
Because of an increasing demand for energy, the BLM is issuing more permits to drill on public land in and adjacent to the Rocky Mountains. Facilitating such energy development is a component of the BLM's multiple-use mission, though there is ongoing public discussion over how much energy development should occur in the Rocky Mountain region.
On BLM-managed public land, a lease and a permit to drill are required to remove oil and gas, and removal must be consistent with the BLM's land use plans, which are developed though a public process. The BLM issues permits after completing environmental analyses required by law. These permits can include stipulations to protect other resources, including wildlife migration routes and nesting areas. Operators are required to minimize environmental impacts during operation, protect important cultural and historic sites, and restore the disturbed site when drilling is completed. By law, energy development is off-limits in National Parks and in congressionally designated Wilderness Areas.
Public land managers seek to balance the national need for domestic oil and gas supplies with requirements to protect ecosystems while meeting all legal responsibilities.
The Rocky Mountains have always inspired awe and respect. Once considered a formidable barrier to be crossed on the way to places farther west, the Rockies today are one of the most sought-after destinations in the world. As more mountain land becomes developed, the open space provided by the public lands becomes increasingly significant. The challenge for public land managers is to conserve the natural resources that attracted people to the mountains in the first place, while allowing continued use and enjoyment of these diverse mountain ecosystems for many years to come. This can be accomplished with the active participation of those who use and care about the public lands, which belong to all Americans.