Portraits of Climate Change: The Rocky Mountains

Lina Barrera

People have been moving westward in North America since the earliest European settlement of the continent. For many early migrants, the Rocky Mountains simply impeded progress toward California and the Pacific coast, but more recent arrivals have come to the Rockies to stay, drawn by their spectacular beauty, agreeable weather, livable communities, and seemingly endless options for outdoor recreation. Between 1990 and 2000 these amenities attracted well over 2 million new residents to the area, and the in-migration has continued into this decade (50,000 came to Colorado last year alone). The area has become a rapid-growth zone; six of the top ten fastest-growing U.S. states lie along the Rockies.

Growth of this magnitude would have brought problems at any time, but the recent spurt has come during an era of increasing stress on natural systems. Drought, resource development, land-use changes, and above all climate change have put the population growth and the region's ecosystems on a collision course.

Ecology and Economy

The Rockies rise from the central plains in the United States and Canada through three distinct ecosystems (montane, subalpine, and alpine; see diagram) on their way to a maximum peak of 4,399 meters (14,433 feet) at Colorado's Mount Elbert. The range extends from Alberta and British Columbia in the north through Montana, Wyoming, Utah, Idaho, Colorado, and New Mexico in the south (see map). The northernmost ranges contain the lowest elevation thresholds for each ecosystem. For example, the front ranges of the Rockies, which ascend from the east, contain most of the lower altitude montane ecosystem; however, in the south the montane can extend all the way to 2,900 meters, whereas in the north the montane transitions to the subalpine at 1,675 meters. Characterized by Ponderosa and lodgepole pine, Douglas fir, and the distinctive, golden-leafed quaking aspen, the montane is the winter home of many of the region's charismatic species, including mule deer, elk, moose, mountain lions (cougars), great horned owls, and black bears.

At 2,750 meters, about the altitude of major ski resorts like Jackson Hole (Wyoming), Aspen (Colorado), and Banff's Lake Louise (Alberta), the landscape transitions to subalpine forest, where typically a mix of Engleman spruce and subalpine fir provides habitat for species such as the yellow-bellied marmot and the snowshoe hare. Harsh conditions increase with altitude and trees begin to shrink in size, so that at the transition between the subalpine and the alpine the ground is carpeted by a dense growth of trees no taller than the rocks and snow that protect them from the wind. Above the last of these stunted trees is the open expanse of the alpine tundra (starting between 2,200 and 3,350 meters), home primarily to hardy flowering plants, such as the lovely dwarf clover and low-lying mosses. Most plants here have adapted by growing long taproots for water and dense hair for wind protection.

The Rockies are already a refuge for numerous populations of animals whose natural habitat ranges have been restricted by construction and human population growth. Wolves and grizzly bears are among the animals that have found unfragmented habitat in the parks and wilderness areas of the Rockies, and they will be most at risk if those habitats disappear. Unfortunately, mountain ecosystems are very sensitive to the impacts of climate change. The higher elevations of the Rockies in Montana, Wyoming, and Northern Idaho have experienced three times the global average temperature increase of 0.74 degrees Celsius (1.3 degrees Fahrenheit) in the last century. These areas not only host many species, but also provide most of the water for western cities and towns, as well as natural space for snow-based winter recreation and many summer activities that underpin key portions of Rocky Mountain state economies.

Those economies often began with hard-rock mining, which was a key attraction for early settlers. Gold was first found in the Southern Rockies in the late 1850s, and by the summer of 1860 5,000 miners were arriving every week. Many towns in the Rockies were built on gold, silver, and copper, and the names of many of the region's towns (both inhabited and not) carry this legacy: Golden, New Mexico; Silverton, Colorado; Goldfield, Arizona; Garnet, Montana. Today, more than half of U.S. coal output is produced in the western states and natural gas extraction has been increasing since the 1980s. The region will also feature prominently as we move toward new forms of energy production, including renewable sources (wind and solar) and more controversial processes like oil shale extraction.

Although extractive industries persist in the Rockies, the economies of many western communities have transitioned away from mining over the past 40 years toward much greater diversity facilitated by the region's wild spaces. People flock to the Rockies for many outdoor activities, including hiking and backpacking, hunting, fishing, whitewater rafting, mountain biking, and skiing. Tourism, a leading contributor of jobs and income, is now vital to the economies of the Rocky Mountain states. For example, in 2008 visitors to Utah spent US$7.1 billion and tourists to Montana contributed $4.31 billion in direct spending and travel-related income, roughly a tenth of the state GDP. Idaho reports that skiers, hunters, and fishers spend more than double what the average visitor to the state spends, and tourism in the region is expected to hold steady throughout 2009 despite the economic downturn. Moreover, tourism is often a catalyst for economic growth and diversification, as inspired visitors seeking a new way of life become settlers and increase demand for a full range of goods and services, from new homes to doctors and entertainment options. As the local economy expands to include new activities and possibilities, such as the growing high-tech sector, the area becomes increasingly "knowledge and amenities driven" and thus attractive to further waves of immigrants.

As a result of these changes, the services sector, defined broadly to include everything from dining, lodging, and entertainment to financial advising, health care, and public services, has added about 20 million new jobs to the western U.S. economy since the 1970s. Meanwhile, employment in agriculture and mining has stayed relatively flat. From 1990 through 2000 the fastest growing sector of the services industry included high-wage, knowledge-based jobs, which accounted for 96 percent of the region's personal income growth. The second fastest growing source of income came from retirement accounts and government payments (such as Social Security), courtesy of the influx of retirees moving to the region.

The vast system of protected lands in the west directly provides many of the amenities that are boosting local economies. A Sonoran Institute study found that western counties abutting or containing public lands display the fastest economic growth in the region. In contrast, those areas more dependent on mining, logging, agriculture, and manufacturing exhibit the slowest economic growth. The combined threats of climate change and development-driven degradation threaten to destroy the amenities delivered by natural areas that are sustaining the region's economic prosperity.

Climate Change in the Rockies

Climate and weather patterns vary significantly from low to high altitudes and from north to south along the Rocky Mountain range, and current research is fragmented across the different states and altitudes. However, there has been a clear upward trend in temperatures across all the continents and major ocean basins in the last three to four decades-increases that exceed anything expected from natural variability-and the Rocky Mountain zone is no exception. As elsewhere, most of its ecosystems cannot adapt to the temperature increases as rapidly as they occur.

Climate sets the parameters for which ecosystems can occur in any given location, determining the vegetation, water availability, and temperature ranges that make an area viable for one species or another. Changes in temperature and water flows alter the vegetation patterns in a region and thus the habitat and food sources available for the animals living there. In the Rockies, for instance, the normally low-elevation Douglas fir has already crept into higher elevations. The upward movement of alpine treelines has also been documented in the northern Rockies. Eventually it may become warm enough that the uppermost ecosystem in the Rockies, the alpine tundra, could disappear, which would trigger the extinction of the well-known resident bighorn sheep.

The Rockies harbor many species with specific habitat and temperature needs that are at risk from a changing climate. The American pika (pronounced pie-ka), for example, is a small, furry relative of the rabbit that is at risk of extinction because of changes to the alpine tundra it calls home. Pika are unable to withstand even a few hours outside their dens in temperatures higher than about 27 degrees Celsius, and they usually nest above 2,400 meters in areas where the temperature rarely exceeds 25 degrees. At least one-third of pika colonies in Nevada and Utah have disappeared in the last century, with warming temperatures being considered a main reason, according to the U.S. Geological Survey. If this trend continues, pika will probably be extinct in 100 years.

A trend of particular concern is warmer winters. The average winter temperature in the U.S. West has risen about 1.4 degrees Celsius over the last century, and with it the amount of snow that accumulates on the mountains (the snowpack) has decreased. The northern Rockies are seeing 15-30 percent less moisture in the spring snowpack (measured according to the amount of water that the snow would produce if melted) since the 1950s, and along the entire range the spring snowmelt is arriving 10-30 days earlier. In Montana's Glacier National Park, the snowpack and summer temperatures have remained relatively constant since 1922, but the average yearly temperature has increased by 1.6 degrees Celsius, rainfall has increased over snowfall, and winter lows have risen. These factors are driving the disappearance of the iconic glaciers: They are expected to be gone by the end of the next decade. (Global satellite data since 1978 show that mountain glaciers and average snow cover have declined worldwide.)

As temperatures warm, winter snow is much more likely to become winter rain, particularly at the middle and lower altitudes where temperatures fall below freezing less often. A "widespread increase" in rain over snow has been identified throughout the western United States from 1949 to 2004, according to a report by the Western Water Assessment for the Colorado Water Conservation Board. These changes will have critical economic effects. For example, less snow means reduced stream and river flows in the spring and summer, and therefore less drinking water for western towns and cities, which derive 75 percent of their water supply from the snowpack. Related declines in species prized by hunters and fishers are also likely to harm mountain-state economies. According to the nonprofit group Trout Unlimited, most populations of trout that inhabit the cold waters of Rocky Mountain streams, mainly bull trout and Bonneville and Colorado cutthroat trout, are already under pressure because of habitat loss. These popular species could lose a further 50-90 percent of their habitat with an increase of 3 degrees Celsius in summer temperatures, well within the predictions of the Intergovernmental Panel on Climate Change of between 1.5 and 5.7 degrees Celsius by the end of the century.

And while businesses catering to hunters and fishers will be hurt, less snow also means that the ski season in the Rockies will be shorter and snow bases shallower. The National Ski Areas Association reports that, despite the economic downturn during the 2008/09 season, resorts with good snow conditions had strong visitation and some even had record numbers in the first half of the season. Those areas with poor snow coverage, however, did less well. The prime ski conditions of the Rockies attract about 35 percent of all U.S. skiers every season, an impressive 21.3 million (out of 60.5 million) in the 2007/2008 season. If conditions decline due to warmer temperatures, the region would lose a major source of revenue.

The earlier spring onset and warmer temperatures also mean longer summers. While this translates to more fun for summer adventurers, it also creates generally drier conditions for a longer period. These conditions can be aggravated by drought, one of several kinds of extreme weather event expected to increase globally due to climate change. Indeed, from 1998 through 2003 the Rockies suffered a major drought, the worst in western North America in 500 years. Wildlife in the region suffered considerably, with some areas reporting big game species foraging for food near roadways where runoff sustained favored vegetation that had died elsewhere. For some species the increasingly dry conditions are a death sentence: 30 populations of bighorn sheep in the southwest United States became extinct between 1900 and the early 1980s due to increased temperature and decreased precipitation leading to a loss of food sources.

The pine bark beetle epidemic, which has destroyed about 800,000 hectares of forest in Colorado alone since the early 2000s, is partially rooted in the warmer and drier temperatures. The beetles are traditionally kept in check by annual die-offs caused by cold weather, but due to the warmer winters the beetles have been breeding twice as often as normal. Subsequently they've caused unprecedented damage to the region's mature stands of pine, especially lodgepole. As the forests are decimated, the species that depend on them will also decline. Scientists predict that the boreal owl, which likes to hunt largely in mature forests, will be scarce for 40-60 years following the end of the beetle epidemic. Populations of snowshoe hare, and therefore lynx and other predators, will also decline for at least 10 to 15 years until the lodgepole pine forests become dense once more.

 Climate change is also increasing the risks associated with wildfires in the West. Although federal, state, and local fire control efforts have long shaped the incidence and location of forest wildfires, climate is increasingly a primary driver as well. A recent study from the Scripps Institution of Oceanography found that the number of fires in the Rockies increased by 400 percent in the 16 years from 1987 through 2003 compared with the previous 16 years (1970-1986). Moreover, the length of time the fires burned also increased, from an average of one week to five weeks. The greatest increase in forest fires occurred in the northern Rockies, where fire suppression has been minimal but where the early onset of spring is significantly reducing the soil moisture by mid-summer. The study found that there were many more fires in warmer years than in cool years, with early snowmelt being a major indicator of a more active fire season. In fact, temperatures were found to account for 66 percent of the variation in fire frequency from year to year (primarily in areas between 1,680 and 2,590 meters). Average spring and summer temperatures in this region have increased by 0.87 degrees Celsius since the 1980s, and because of the added warmth and dry conditions, the fire season is now starting earlier and ending later than in the past. (Parenthetically, drier soils, when disturbed-possibly by increased off-road vehicle activity, livestock grazing, and oil and gas development-may be behind a rising incidence of regional dust storms, which leave dark soil layers on the snowpack that tend to accelerate melting.)

Fighting wildfires already costs $1 billion per season in the United States (and is a grave problem elsewhere as well, as demonstrated by Australia's recent experience with a string of savage fires that claimed more than 200 lives and 2,000 homes). Unfortunately, experts predict that the area burned by wildfires in the western United States will double by 2100, hitting Montana, Wyoming, Utah, and New Mexico particularly hard. Worse, the forests of the western states account for 20-40 percent of the carbon sequestration in the country; if they are destroyed by fires then they will cease to function as carbon sinks and very possibly could become net emitters of CO2. The Australian fires are estimated to have increased the country's total annual carbon footprint by up to 20 percent in just a few days.

As fires continue to grow in size and duration, the composition of forests will change as open, sunny spaces are created that are unsuitable for native species but inviting for invasive species. At least 37 problematic invasive species of fish, amphibians, plants, insects, and diseases are expected to increase their ranges in the United States as a result of climate change.


An estimated 25 million new residents will move to the western United States in the next quarter century. The Rocky Mountain region will receive a substantial portion of this influx, guaranteeing continuing encroachment of open spaces, even if some portion of the region remains protected. Residential development has been rising in the region since the population boom in the 1970s, when western states grew their populations by 40 percent.

Colorado's chapter of The Nature Conservancy estimates that approximately 80 percent of the state is still relatively undeveloped, but is quick to point out that the impacts of development are felt well beyond the edge of any given housing complex or new pipeline because connecting roads bring additional development, access to formerly isolated natural areas, and increased demands for resources. Major impact in the Rockies spreads out along the Interstate highway corridors, with I-25 forming a north-south access pathway along the Front Range on the eastern edge of the chain, and along I-70 and I-90 reaching west over the mountains. The resulting habitat fragmentation makes it difficult for species to move as they try to adapt to changing climatic conditions. Formerly, the combination of public lands and large private ranches maintained significant open space and important buffers between wild and urban areas, but now such farms and ranches are being divided into small-lot residential developments that increase habitat fragmentation, one of the largest threats to species survival in the region. Large species, especially, need intact migratory corridors. Pronghorn, a beautiful antelope-like native species, already struggles as it attempts to travel its yearly migration path, which is now cut by fences and roads. The size of the Wyoming herd of pronghorn has declined 40 percent since 1984, according to Brian Maffly, writing in National Wildlife magazine. Season's End, a report sponsored by a consortium of hunting and fishing groups, expects that mule deer and elk will eventually disappear from the intermountain West.

Valuable habitat is also under threat from energy development, which is on the rise. The federal Bureau of Land Management in 1999 issued 1,803 permits for drilling on public lands, but by 2007 that number had more than tripled to 6,399, most in Colorado, Montana, New Mexico, Utah, and Wyoming. As the cost of traditional fuel fluctuates and concerns about carbon dioxide concentrations grow, the pressure to find both domestic conventional and alternative energy sources increases. The western United States holds great wind and solar energy potential, but the Rockies are also being eyed for natural gas development and the even more controversial process of oil shale removal, which extracts oil from rocks by heating the ground and then pumping the liquefied oil to the surface. The targeted area for this process, the Green River Formation, is one of the most valuable areas of wildlife habitat in the Rockies. Situated on the shared border between Colorado, Utah, and Wyoming, the Formation is home to mule deer, elk, mountain lions, black bears, and bald eagles. Oil shale extraction would not only degrade this unique area, but would also demand vast amounts of water and energy, producing more greenhouse gas emissions than traditional oil extraction. Also at risk are millions of hectares of important fish and game habitat that harbor recoverable oil and gas in Montana, Wyoming, Utah, Colorado, and New Mexico.

Water, Water...Not Everywhere

Finally, looming over all the other challenges facing the region, is water. Stories of gunfights sparked by conflicts over water rights are standard fare in recounting life in the old West. Today there are complex agreements and adjudication processes to resolve these conflicts in a more civilized, if still contentious, manner. Increased scarcity from climate change, coupled with skyrocketing population growth, will add to the already complicated dynamic in the region.

Most of the water supply in the western United States (except for a few rivers rising in the Sierra Nevada mountains and watering parts of California) typically comes from rivers originating in the Rocky Mountains. Additionally, winter snow that falls in the Rockies and melts slowly throughout the spring and summer replenishes groundwater supplies in the plains and feeds the streams that eventually fill reservoir systems. All told, the Rockies provide more than 75 percent of the water supply for cities, towns, and primarily farms throughout the western states. Most of the water (80-90 percent) in the region goes to agricultural production, which in the Colorado River basin produces about 15 percent of the nation's crops and 13 percent of its livestock.

Water rights in the western United States are determined on what is essentially a "first come, first served" basis, where the first person to divert water for "beneficial use," such as irrigation or municipal use, receives the rights to that water. In times of scarcity, priority goes to the person with the earliest claim, so that subsequent, or "junior," claimants may end up with nothing at all. When water crosses state lines, it is managed by legally binding "compacts," such as the 1922 Colorado River Compact. This agreement provided the basis for a series of intricate, comprehensive water allocation arrangements dividing Colorado River water among 30 million people in seven states: Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming.

Climate change affects the amount of water available in the region through various chain reactions. As snowfall and snowpack decline with rising temperatures, river flow reductions are expected. The annual flow of the Colorado River, for example, is 90-percent dependent on runoff from high-elevation snowpack in Wyoming, Colorado, and Utah. Researchers at the University of Washington predict that as the ambient temperatures continue to rise, moisture levels in snowpack will drop by 30 percent by the end of the century and runoff will decrease 17 percent. The study finds that under these conditions the water stored throughout the Colorado River basin will drop by almost half, and the release of water from the upper to the lower basin that is mandated by the Compact will only be met between 60 and 75 percent of the time by 2025. These forecasts are corroborated by a new study from the U.S. National Center for Atmospheric Research concluding that water flows in the world's largest rivers, including the Colorado, have declined in the last half-century, mostly as a result of climate change. Other rivers fed by Rocky Mountain snow, such as the Snake River in Idaho and the North Platte in Wyoming, are likely to see similar impacts.

Currently there is no discernable trend, up or down, in precipitation levels throughout the range, largely because of the considerable natural variability from site to site in the Rockies. So while climate change is expected to increase rainfall globally, which could provide a glimmer of hope for mountain-fed water sources, climate models disagree if, and how, this might affect the Rockies. What models can predict is that even if precipitation increases along with temperature there will still be a net loss in runoff in the Rockies because of increased evaporation due to heat.

In 2006 the International Water Management Institute estimated that 1.6 billion people are living in areas of "physical water scarcity," where water is not available either because of an arid climate or because the resources have been overcommitted to multiple users. These areas include the region south and west from the central Rockies to central California and Mexico. In response to anticipated changes in both supply and demand for water, water managers in the region are implementing new conservation measures and water recycling programs, but the savings from these won't be nearly enough to mitigate the expected changes. If the cities and towns in the Rockies are to keep growing, then agriculture, the biggest water user in the region, will have to reduce its consumption. Efficient irrigation systems will be one option. Ultimately, however, the most likely scenario, according to Brad Udall of the Western Water Assessment, will involve the directing of water toward the most productive sectors of society. At this time, those are the "amenities and knowledge" portions of the economy. It may be a slow and painful process, particularly for those communities that are deeply rooted in agriculture, but eventually this water-intensive portion of the economy will be drastically reduced. This is not an uncommon coping mechanism for areas with water shortages; Middle Eastern countries have long minimized their water stress by importing food so that they can use all of their water for other purposes.


Climate change poses severe challenges to the Rocky Mountain region as well as to the rest of the globe. So far, the response has been mixed. The key message of the landmark 2006 Stern Review on the Economics of Climate Change is that we don't have to choose between controlling greenhouse gas emissions and continuing to grow our economies. The Review estimated the cost of reducing greenhouse gas emissions at 1 percent of global GDP per year in perpetuity (in a later revision this was raised to 2 percent), while unmitigated climate change impacts will cost at least 5 percent of GDP per year, and possibly as much as 20 percent per year, in perpetuity.

Taking note of this are several states tired of waiting for national action, including Arizona, California, Montana, New Mexico, Oregon, Utah, and Washington, and the Canadian provinces of British Columbia, Manitoba, and Quebec. This coalition recently launched the Western Climate Initiative, a regional cap-and-trade program to reduce greenhouse gases from all major sources. The expectation is that a cap on carbon will not only help reduce emissions but will also spur investment in new technologies and feed the regional economy. Meanwhile, President Obama has since asked Congress to enact a national cap-and-trade program, and expectations are that it will become law in 2010. This act would set the entire country on a path to mitigating climate change, and would enhance efforts to minimize its damaging effects on the wild places of the Rocky Mountain region. However, this hardly means that there are no threats from booming populations, ongoing sprawl, further oil shale and natural gas development, and the impacts of the changes in climate that we have already put into motion.

If the Rocky Mountain states want to continue to see growing, robust economies and levels of personal income as well as the quality of life that is so appealing, then the smart money is on investing to protect natural, amenity-producing areas throughout the region from the impacts of spreading development. This, of course, will not protect the Rocky Mountain ecosystems from the impacts of climate change, which is ultimately a global phenomenon, driven by choices made by people and governments all over the world. The Rocky Mountains are already changing in response to climate shifts, but to protect them from further severe climate change will require global action to reduce greenhouse gas emissions in what will amount to a fundamental transformation of our energy systems and many other aspects of our lives, from transportation to jobs. The world's attention is focused on Copenhagen, where a new post-Kyoto agreement on climate change will be debated this December and will either move the global community toward a collective transformation or leave us in a continued state of denial and piecemeal attempts at mitigation.

Lina Barerra has a graduate degree in geography from the University of Cambridge and has worked in international conservation, specializing in the impacts of development on ecosystems, for eight years. She lives in Colorado.