Tundra |
Tundra |
Tundra occurs near the North Pole and on high mountaintops. There are two types of tundra in the world: Arctic and alpine. Arctic tundra forms a band around the North Pole. Alpine tundra is found on the tops of tall, cold mountains.
Courtesy of John and Karen Hollingsworth, U.S. Fish and Wildlife Service Art Explosion The Arctic National Wildlife Refuge in Alaska is the nation's largest refuge. It is in northeastern Alaska, above the Arctic Circle. Alpine tundra can be found below the Arctic Circle in tall mountain ranges such as the Rocky Mountains.
Tundra covers about one-fifth of Earth's land surface. Because of the cold climate trees cannot grow. The tundra biome looks like prairie land, only frozen.
The most distinctive characteristic of the tundra soil is permafrost. Permafrost is a permanently frozen layer of ground. Permafrost can also be found in the coldest regions of the taiga. During the short summers in the tundra, the top section of the soil may thaw out. This allows plants and microorganisms to grow and reproduce. These plants and microorganisms become dormant during the cold winter months.
The name tundra comes from the Finnish word tunturia, a treeless, marshy area. Summers are short in the tundra, but the days are long. This is the land of the midnight sun. During the summer the North Pole is oriented toward the Sun as Earth rotates. Around the time of the summer solstice in June, the Sun never dips below the horizon in the Northern Hemisphere.
Winters are long and cold in the tundra. Days are short. During the winter solstice in December, the Sun doesn't come above the horizon. At noon the sky is in twilight, with the Sun just below the horizon.
Temperatures during the Arctic winter can dip to –51°C (–60°F)! Average temperature during the warmer summer months is between 0°C (32°F) and 10°C (50°F). Sometimes as few as 55 days per year have a mean temperature higher than 0°C (32°F). The average annual temperature is only –12°C to –6°C (10°F to 20°F).
Data from Missouri Botanical Garden Even with very low amounts of rainfall, the tundra stays wet and marshy through the summer.
The Arctic tundra may receive less than 11 centimeters (4.4 inches) of precipitation a year, but the area is still very wet in summer because the water that comes from the melting ice has nowhere to go. During the summer, the whole landscape is open, gently rolling ground, covered with many small lakes and ponds. The ground between the ponds is soggy with water rich in nutrients from decaying organic material.
Snow covers the ground throughout the long winter. It serves as an insulating layer, protecting plants and providing shelter for small mammals. Brown lemmings dig tunnels through the snow and eat twigs and bark from dormant plants without leaving the protection of the snow.
Plants that survive in the tundra grow close to the ground. Naturalists in parks with alpine tundra (e.g. Rocky Mountain National Park) call the tundra flowers "belly flowers"—to get the best look at them, you need to get down on your belly.
Courtesy of Denali National Park Art Explosion Reindeer lichens provide food for browsing animals. They are the primary diet of caribou during the winter. Plants in tundra are very small and close to the ground. This form protects them from harsh, cold winds.
Where soil accumulates in pockets or cracks in rocks, small shrubs may grow. The constant freeze-thaw cycle that happens in the tundra helps crack rocks into smaller pieces. Lichens, a combination of a fungus and an alga living and growing together, are unusual organisms that grow on the rock surfaces and in cracks.
Some plants have dark red leaves. The red color helps them absorb more solar energy in this cold climate. Tundra plants are often quite small and require few nutrients. Smaller branches and leaves also help plants retain heat and reduce transpiration of water in the cold conditions.
The frigid cold and deep snow make life in the tundra very difficult. Animals that live in the tundra include Arctic fox, caribou, golden eagle, gray wolf, musk ox, brown lemming, brown bear, red phalarope, and ruddy turnstone. Animals in the tundra are adapted to survive cold winters and to breed and raise young quickly in the very short, cool summers. Some animals grow thick fur to keep warm. Others hibernate during the winter months. Ground squirrels hibernate and live off the fat they stored during the spring and summer. Some of these animals can live in other biomes, like the taiga. Herds of caribou migrate south to warmer climates during the winter.
Courtesy of Dean Biggens, U.S. Fish and Wildlife Service Courtesy of Dick Hensel, U.S. Fish and Wildlife Service Caribou are members of the deer family and are found in the Arctic regions of Alaska and Canada. Both males and females carry antlers. The antlers include a unique brow tine, sometimes called a shovel, which is used to sweep snow off the ground and discover food. Snowshoe hares range in Canada and the northern most parts of the Unites States. The hare eats grasses and plants in the spring and summer. During the winter months it eats roots and bark. The main predators of the snowshoe hare are coyotes, lynx, weasels, and foxes.
Courtesy of Tim McCabe, U.S. Fish and Wildlife Service Courtesy of Jo Keller, U.S. Fish and Wildlife Service Canada geese are perhaps the most familiar of all the wild North American geese. Musk ox are hoofed mammals found in the Arctic reaches of North America, Greenland, and Siberia. Their outer coat of long hollow guard hairs and inner coat of fine, thick underhair, or "qiviut," insulate them against the extreme cold. They have large, sharp, curved horns.
Many birds migrate to the tundra region for the summer. These birds include the Pacific loon, tundra swan, snow goose, and sandhill crane. The melting snow forms shallow ponds in the permafrost. These conditions are perfect for mosquitos and other insects to lay their eggs. The insects provide a rich source of food for the birds that migrate to the tundra to nest each spring.
Human activity in the Arctic tundra has raised many environmental issues. The tundra is vulnerable to human intrusion. The oil spill from the Exxon Valdez in Prince William Sound off Alaska in March 1989 released 250,000 barrels of oil into the ocean. This spill damaged the tundra coast, harming or killing animals and plants that made this area their home.
Air pollution is another source of possible harm. The release of harmful substances in smoke from a nickel refinery and other plants in Russia is a concern to neighboring Scandinavian countries that are trying to protect tundra.
Another looming issue is disturbance of the caribou herds as they migrate from their winter range to their summer calving areas. Oil pipelines and oil drilling cause severe disturbances.
Courtesy of Alyeska Pipeline Service Company Courtesy of Alyeska Pipeline Service Company The pipeline crosses three mountain ranges as it carries oil 1280 kilometers (800 miles) to the sea: the Brooks Range, the Alaska Range, and the Chugach Mountains. At its highest point, Atigun Pass, the pipeline reaches an elevation of 1440 meters (4739 feet). It also crosses 34 major rivers and streams, including the Yukon, Chena, and Tanana Rivers. This is one of many pump stations along the Alaska pipeline.
Other concerns are road building, strip mining, vehicle movement, and other human activity across the tundra. When oil and gas were discovered in the tundra, these activities increased. The effect on frozen tundra ground was devastating in some areas. Because of the short summer growing season, damaged vegetation takes many years to recover. Many areas of swamp and uneven terrain were created, especially because people didn't understand the damage they were doing.
Human activity has also influenced the wildlife of Arctic tundra. Polar bear, walrus, musk ox, and caribou have become less common because of hunting. The danger has been recognized, and protective legislation has been approved (international agreement on protection of the polar bear, achieved in 1973, was a landmark in this process). Many concerned countries created national parks and wildlife refuges in the late 20th century.
Another issue for the tundra is the affect that global warming might have on the area. Changes in Earth’s temperature would greatly affect the extreme northern and southern regions of the world. Polar regions such as Alaska, the Arctic, and Antarctica contain a wide variety of physical features and ecosystems. These ecosystems are sensitive to very small changes in air temperature, ocean temperature, and other climatic conditions. Changes in temperature may cause tundra areas to become more like taiga or northern forests.
Already, arctic temperatures during the late 20th century appear to have been the warmest in 400 years, and the extent of snow cover has declined by 10 percent since the late 1960s. In addition, the time that the lakes and rivers are frozen over has decreased by two weeks.