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Glacier National Park"Glacier's ecosystem has already altered in response to climate change."
- Daniel Fagre, Research Ecologist
U.S. Geological Survey, Glacier Field Station |
Today's climate may be too warm to sustain the park's mountain glaciers long-term. Researchers estimate that even if average temperatures were to remain at their current level, all the glaciers would disappear within the next 100 years. If warming in the region proceeds as expected, the glaciers will be gone much sooner, probably by the year 2030.
The size of the park's glaciers already is affected by changes in climate. For example, the glaciers retreated dramatically from 1920-1940, when the region experienced above-average summer temperatures and below-average annual precipitation. From 1960-1979, temperatures dropped, precipitation increased, and some of the larger glaciers actually grew slightly. Since that time the glaciers have receded farther.
Glacier National Park is not the only area where glaciers are melting. Mountain glaciers in the Alps, south-central Alaska, and the Pacific Northwest also have retreated over the past century.
Fish in the FutureImagine casting a line into the Flathead River at Glacier National Park and not finding any trout. Or picture a fly fisherman revisiting the Madison River in Wyoming in the future and catching only half the cutthroat trout of today. This kind of scenario could become reality sometime in the next 100 years.
A recent EPA study found that a moderate warming of 4.5°F over the next 70 years could cut the habitat of brook, rainbow, and cutthroat trout by one-fourth to one-third nationwide, with similar habitat losses for chum, chinook, pink, and coho salmon. Habitat losses are not evenly distributed around the country. For example, rainbow trout habitat is projected to decline by only 9 percent in Washington, whereas Pennsylvania, New York, Ohio, Indiana, and Illinois collectively lose 86 percent of their baseline habitat for rainbow trout. When added to existing threats such as whirling disease and other exotic diseases, climate change could be stressful for many cold-water fish.
Cutthroat trout, rainbow trout, and other fish in the trout and salmon family require cold water. These fish, and the cold-water invertebrates they feed on, could lose habitat as the climate becomes warmer. The loss of mountain glaciers, warmer air temperatures, reductions in winter snowpack, and changes in the timing and rate of spring snowmelt could make many streams too warm for cold-water fish.
Streamflows altered by changes in rainfall and snowfall could affect fish populations. The young of some species of native trout hatch in summer when snowmelt is declining, while others hatch in spring before runoff occurs. Warmer winters could increase the occurrence of rain falling on snow, which may harm incubating eggs of trout that spawn in the autumn.
Changes in streamflow and temperature may affect insects and other invertebrates that live in streams and are important food sources for fish. In the McDonald Basin of Glacier National Park, for example, the distribution of six species of caddisfly larvae in streams is closely related to water temperature. If water temperatures change, the variety and abundance of invertebrates living in stream water are likely to change as well. |
In addition to the melting glaciers, a warmer climate could cause declines in snow cover, reductions in trout populations, the loss of rare alpine plants, and changes in forest composition in Glacier National Park.
The park has a wide range of habitats and climatic conditions that are responsible for the area's rich biological diversity. Mountains rise abruptly from the prairies, and the east and west sides of the Continental Divide exhibit a sharp contrast in climate. The park includes soils that are rich in calcium as well as soils that are calcium-poor, each supporting a very different community of plants and animals. Various parts of the park contain plants that are typical of the northern Rocky Mountains, the Great Plains, the Pacific Northwest, boreal regions, and Arctic-alpine regions. Each of the three major river systems in the park (Missouri, Columbia, and Saskatchewan) also has its own distinct aquatic community.
Global warming could lead to many complex changes in the park's plant and animal communities, including shifts in the treeline and changes in stream and lake communities. Such changes have occurred naturally during past climatic changes and will occur naturally in the future. The difference is that now humans may be increasing the pace and magnitude of climate change.
Yellowstone National ParkGlobal warming may result in a warmer and drier climate in the Yellowstone region, increasing the risk of forest fires. Some computer models project a warmer and wetter climate, but the trend over the 20th century was toward warm and dry.
Since the massive fires of 1988, when nearly half of Yellowstone National Park burned, scientists who study the area have paid close attention to climate change. The number of fires and their severity depends on many factors other than climate, such as fuel management practices (e.g., prescribed burns and the thinning of forests) and the effectiveness of fire suppression efforts. But climate and weather clearly play a role. Experts agree that the fires of 1988 came about as result of a winter drought, a hot dry summer, and unusually strong winds.
Also important were the large areas of highly flammable, old-growth lodgepole pine forest. Under normal conditions, large fires like those of 1988 occur only once in every few generations. But with approximately 40 percent of Yellowstone still vulnerable to large-scale burns, any increased fire risk due to climate change could pose a significant problem.
Ducks in PerilFrom 50 to 80 percent of North America's ducks and other waterfowl nest in the prairie pothole region of the north-central United States and south-central Canada. The shallow prairie wetlands are vulnerable to drought, and computer models indicate that global warming is likely to bring stronger and more frequent droughts to the prairie pothole region.
According to one study, global warming could cause the number of prairie ponds in the north-central United States that hold water in the spring to drop from today's average of 1.3 million to just 0.6-0.8 million by the year 2060. The loss of habitat could reduce the average number of ducks settling to breed in the north-central United States from 5 million birds today to between 2.1 and 2.7 million by the year 2060.
Duck populations reached historical lows in the 1980s due to a combination of prolonged drought, the loss and degradation of habitat, and land use changes that favored predators. In recent years, better water conditions and intensive wetland conservation and management programs have helped duck populations rebound.
When the prairie potholes dry up during drought years, waterfowl normally move north to nest in the parkland potholes of Alberta and Manitoba — pothole wetlands that are surrounded by aspens and willows. But researchers have found that many parkland potholes also may dry up in the future as the climate changes, leaving ducks with fewer potential nesting sites.
What can be done to protect the pothole region from the potential effects of global warming? Scientists recommend that we start by conserving the least drought-sensitive areas so they are available to birds in the future as the climate warms. |
Fire plays an important role in several ecosystems in the region, including sagebrush steppe, western juniper woodlands, and ponderosa pine forests. In the past, frequent low-intensity surface fires perpetuated ponderosa pine stands with grassy undergrowth. Today, after 60 years of policies to prevent and suppress forest fires, many ponderosa and lodgepole pine forests have high densities of trees, are plagued by epidemics of insects and diseases, and are subject to severe fires that can destroy entire stands of trees. The trees' high density could lead to more frequent and more damaging outbreaks of defoliating attacks by western spruce budworms. Insect outbreaks have occurred many times in the past, but fire suppression policies and climate change may exacerbate them in the future. The replacement of old-growth forest stands by younger stands could affect some of the park's plant and bird species, such as the northern twinflower, fairy slipper, pine martin, and goshawk.
Even a modest warming and drying could reduce the habitat of whitebark pine by up to 90 percent within 50 years. Whitebark pine populations already are declining because of the white pine blister rust fungus and other invasive exotic pests. Whitebark pine nuts and army cutworm moth caterpillars, which are found in these forests, provide vital food for the region's grizzly bear population. Whitebark pine forest may be replaced with Douglas fir, and on the lower slopes, forest would give way to treeless landscapes dominated by big sagebrush, Idaho fescue, and bluebunch wheatgrass.
Climate change also could cause high alpine ecosystems to shrink in many areas. Local extinctions of alpine species such as arctic gentian, alpine chaenactis, rosy finch, and water pipit could be expected as a result of habitat loss and fragmentation.
Parks in the Pacific NorthwestThe impacts of climate change in North Cascades, Mt. Rainier, and Olympic National Parks may be similar to those affecting Glacier National Park. If the regional climate follows the global trend toward warming, scientists expect receding glaciers, warmer stream waters, changes in plant and animal communities, and increased risk of fire.
North Cascades National ParkNorth Cascades National Park contains more than 300 glaciers, accounting for approximately a third of all the glaciers in the lower 48 states. Since the end of the Little Ice Age in the late 1800s, glaciers have retreated throughout the park area. Although historical data on the glaciers' size are scant, scientists believe that several dozen glaciers may have disappeared during that time.
Warmer temperatures and disappearing glaciers could harm the five species of salmon — sockeye, pink, coho, chum, and chinook — that rely on rivers in the park. Some streams in the North Cascades can support salmon only because the streams are fed by glacial meltwater. Salmon in the region already face immediate stresses from human activities outside the park.
Olympic National ParkAbove the old-growth temperate rainforest, the high alpine and subalpine meadows of Olympic National Park come alive with wildflowers every spring. Future hikers may experience only a fraction of today's colorful displays, as some meadows may give way to forests moving upslope in response to changing climate.
Fire, the length of the growing season, and soil moisture are among the factors that determine the growth and distribution of alpine and subalpine plants. All of these natural processes are sensitive to climate change, and changes in any of them could produce conditions favorable for trees to invade the meadows.
In fact, changes already are occurring at the treeline: Forest species are beginning to crowd the edge of the meadows and fill the gaps of open grassland. Furthermore, computer simulations suggest that in the future, a warmer climate will allow trees to become established in all current meadows.
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