Portraits of climate change: the Rocky Mountains.

• Author: Barrera, Lina

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.

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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.

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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.

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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 GDR 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...