| |
 Melting Glaciers, Changing EcosystemsThe glaciers in Glacier National Park are shrinking. Today, the park's largest glaciers are only about a third of the size they were in 1850, and many small mountain glaciers have disappeared completely during the past 150 years. The area of the park covered by glaciers declined by 73 percent from 1850-1993. The cause? A regional warming trend that some scientists believe may be related to global climate change. Since 1900, Glacier National Park's average summer temperatures have increased by about 1.8 degrees Fahrenheit.
Park visitors can experience the scale of glacial retreat by hiking the trail to Upper Grinnell Lake, where a series of signs mark the former end points of Grinnell Glacier. The glacier once covered 576 acres on the eastern slope of the Continental Divide. To reach its terminus today, one must climb steadily upward through an area that was covered with ice in the 1850s. Still farther uphill is the sign marking the terminus in the 1930s, still higher the 1960s, and finally the 1980s. Today the remnants of Grinnell Glacier — one of more than 50 mountain glaciers in the park — are reached just below the summit of Mt. Gould. The glacier has shrunk by more than 62 percent since 1850 and now covers barely 200 acres.
"It's increasingly hard to understand why it's called Glacier National Park, because the glaciers are getting hard to find."
- Bruce Babbitt, Secretary of the Interior
October 7, 1998 |
If scientists' predictions are accurate, Grinnell and all of the park's other glaciers will disappear entirely within the next 30 years.
Melting glaciers are only part of the story. Experts believe that climate change will have wide-ranging impacts on fish, wildlife, trees, and plants throughout the western mountains and plains.
In some areas, a warmer climate could cause streams to become too warm to support trout, salmon, and other cold-water fish. If mountain snowpacks decline, summer soils and vegetation may become drier, increasing the risk of fire. Changes in stream flow and water temperature also could affect insects and other invertebrates that live in streams and rivers, with repercussions up the food web on fish, amphibians, and waterfowl.
Impacts at a Glance
- Continued warming could melt all the glaciers in Glacier National Park by 2030.
- Mountain glaciers in many other parts of the world, including the Pacific Northwest, also may disappear.
- Snow cover may be reduced, leading to drier conditions downstream.
- Warmer mountain streams may harm trout and other cold-water species, adding to existing stresses such as whirling disease.
- Yellowstone National Park may experience more frequent fires if the climate becomes drier.
- Plant species distributions may change as the climate changes.
- Rare alpine plants may become increasingly rare under warmer conditions.
- Some plants and animals in alpine lakes above treeline may disappear locally as treelines move higher and lakes warm.
- Global warming could reduce populations of ducks and other waterfowl that breed in the prairie pothole region of the north-central United States and south-central Canada.
|
Climate change may affect agriculture in the plains states, the heart of the nation's breadbasket. It also may affect ducks and other waterfowl by increasing the severity and frequency of drought in the continent's major duck breeding area — the prairie potholes and parklands of the north-central United States and south-central Canada.
Another hazard — forest fire — may occur more frequently in Yellowstone National Park if the climate becomes drier. Fire frequency depends on localweather, sources of fuel and ignition, and the effectiveness of fire suppression. Climate change also could reduce the abundance of whitebark pines and army cutworm moths, two favored foods of grizzly bears. Whitebark pines already are in decline, primarily due to a fungus known as white pine blister rust.
If the region's climate continues to warm in the future, forests of lodgepole pine and western cedar in Glacier National Park may gradually be replaced with forests dominated by spruce and western hemlock. Treelines are expected to move upslope at a rate of roughly 350 feet for every degree Fahrenheit of warming. Alpinemeadows may be invaded by fir trees, and rare alpine plants may disappear locally as conditions change.
A History of ChangeThe western mountains and plains always have been subject to major natural disturbances such as fires, avalanches, landslides, windstorms, floods, droughts, and pest invasions. It would seem like the region's plants and wildlife would be able to handle a gradual change like global warming.
But fires and floods are short-term events. Long-term changes in average conditions, such as those caused by global warming, exert very different forces on ecosystems. For example, an overall warming may allow low-elevation plants and animals to move upslope and invade habitats currently occupied by high-elevation species. Changing conditions may benefit some species more than others, causing the composition of natural communities to change. A single fire may make no noticeable long-term change in an ecosystem. But if conflagrations become more frequent, fire-adapted trees such as lodgepole pine, Douglas fir, and western larch may become more common and expand their range in areas such as Yellowstone National Park.
Although dramatic changes in climate have occurred in the Earth's past, and some of the current global warming trend may be natural in origin, many scientists believe that the world will warm more rapidly during the next 100 years than it has at any time in the past 10,000 years. That rate of change may have significant effects on natural ecosystems and individual plant and animal populations.
What is Global Warming?The Earth's climate has changed in the past, and will continue to change naturally in the future. Ice ages, long warm periods, and short-term fluctuations in temperature and precipitation are all elements of the global climate's natural variability.
Today, the average global temperature is rising. Is that natural? Some of the temperature increase can be explained by natural factors. But many scientists believe that a portion of the warming trend may be caused by humans. Human activities are creating a buildup of greenhouse gases — primarily carbon dioxide, methane, and nitrous oxide — in the atmosphere. The heat-trapping property of these gases is undisputed. Although scientists do not know exactly how the Earth's climate responds to increases in greenhouse gases, they do know that the current warming trend is consistent with changes that would be expected from the increase in greenhouse gases.
Scientists generally believe that the burning of fossil fuels and other human activities are the primary reason for the increased concentration of carbon dioxide in the atmosphere. Fossil fuels burned to run cars and trucks, heat homes and businesses, and power factories are responsible for almost 99 percent of U.S. anthropogenic carbon dioxide emissions and about 20 percent of our nitrous oxide emissions. Of the carbon dioxide emissions, industrial activity accounted for 33 percent in 1997. Personal and commercial transportation accounted for 30 percent, and residential and commercial energy use accounted for 19 and 16 percent, respectively. Increased agriculture, deforestation, landfills, industrial production, and mining also contribute a significant share of carbon dioxide, methane, and other greenhouse gas emissions.
Average global temperatures at the Earth's surface have increased 0.6-1.2°F since the late 19th century. The 10 warmest years in the 20th century all occurred in the last 15 years. Snow cover in the northern hemisphere, floating ice in the Arctic Ocean, and the areas covered by mountain glaciers have all decreased. Globally, sea level has risen 4-10 inches during the past century. Worldwide precipitation over land has increased by about 1 percent, and the frequency of extreme rainfall events has increased throughout much of the United States.
Although it is impossible to predict future changes in climate with certainty, many scientists believe that the continued addition of greenhouse gases to the atmosphere is likely to raise the Earth's average temperature by several degrees in the next 100 years. Rising global temperatures are expected to raise sea level and change precipitation and other local climate conditions. Changing regional climate could alter forests, crop yields, and water supplies. It also could threaten human health and harm birds, fish, and many types of ecosystems. |
What Can Be Done?
To address the threat of climate change, first we have to understand the risks. The potential impacts of climate change also should be considered within the context of other stresses that affect natural areas today, such as invasive species, pollution, and habitat loss.
Scientists currently are analyzing how climate change might affect natural ecosystems in many national parks and preserves, including Glacier, Yellowstone, Olympic, and North Cascades National Parks.
Prevention of human-induced climate change also is an important strategy. Some global warming probably will occur no matter what we do, because some of it is natural. But also, humans have become dependent on fossil fuels. The burning of fossil fuels emits greenhouse gases, which may remain in the atmosphere for years, decades, or even centuries, exacerbating the natural warming. But we as individuals can take action now to reduce our own consumption of fossil fuels by improving energy efficiency and using alternative energy sources. (See "Searching for Solutions" and "What People Can Do".)
|
|