Major Biomes of the World
Have you visited any biomes lately? A biome is a large ecosystem where plants, animals, insects, and people live in a certain type of climate. If you were in northern Alaska, you would be in a frosty biome called the Arctic tundra. If you jumped on a plane and flew to Brazil, you could be in a hot and humid biome called the tropical rainforest. The world contains many other biomes: grasslands, deserts, and mountains, to name a few. The plants and animals living in each are as different as their climates. Which is your favorite?
The Arctic tundra is a cold, vast, treeless area of low, swampy plains in the far north around the Arctic Ocean. It includes the northern lands of Europe (Lapland and Scandinavia), Asia (Siberia), and North America (Alaska and Canada), as well as most of Greenland. Another type of tundra is the alpine tundra, which is a biome that exists at the tops of high mountains.
This is the earth's coldest biome. Since the sun does not rise for nearly six months of the year, it is not unusual for the temperature to be below -30°F in winter. The earth of the Arctic tundra has a permanently frozen subsoil, called permafrost, which makes it impossible for trees to grow. Frozen prehistoric animal remains have been found preserved in the permafrost.
In summer, a thin layer of topsoil thaws and creates many pools, lakes, and marshes, a haven for mosquitoes, midges, and blackflies. More than 100 species of migrant birds are attracted by the insect food and the safe feeding ground of the tundra. Other animals that live in this biome include polar bears, Arctic foxes, caribou, and grey wolves. Plants that you might find include small shrubs and cushion plants, and the lichen which cover the many rocks on the tundra's terrain. The Arctic is also famous for the beauty of its flowers during early autumn.
The coniferous forest biome is south of the Arctic tundra. It stretches from Alaska straight across North America to the Atlantic Ocean and across Eurasia. The largest stretch of coniferous forest in the world, circling the earth in the Northern Hemisphere, is called the “taiga.” It supplies the bulk of the world's commercial softwood timber, which is used to make paper.
These forests consist mainly of cone-bearing trees such as spruce, hemlock, and fir, which are well suited to the cold climate. The soil is not very fertile, however, because there are no leaves to decompose and enrich it. Some animals that thrive in this biome are the ermine, the moose, the red fox, the snowshoe rabbit, and birds such as the crossbill and the great horned owl.
This biome is in the mild temperate zone of the Northern Hemisphere. Major regions are found in eastern North America, Europe, and eastern Asia.
Deciduous trees lose their leaves in fall. The natural decaying of the fallen leaves enriches the soil and supports all kinds of plant and animal life. The deciduous forest is a lively place, where oak, beech, ash, and maple trees are typical, and wildflowers, berries, and many types of insect and animal life abound. But the fertile soil is also good for people, and in Europe most of the deciduous forest has been destroyed to make room for farms and homes. In the U.S., the deciduous forest is a home for deer, American gray squirrels, wood mice, rabbits, raccoons, woodpeckers, cardinals, and finches, to name a few.
A desert is an area where little or no life exists because of a lack of water. Scientists estimate that about one-fifth of the earth's land surface is desert. Deserts can be found on every continent except Europe. There are two different kinds: hot and dry (such as the Arabian and Sahara deserts) and cold and dry (such as Antarctica and the Gobi desert).
In North America, there are four major deserts: the Great Basin, the Mojave, the Sonoran, and the Chihuahuan. All but the Great Basin are hot deserts located in Mexico and the southwestern part of the United States. The Great Basin covers parts of Idaho, Nevada, Oregon, and Utah, and is considered a cold desert.
The lack of water and intense heat or cold make this biome inhospitable to most life forms. Most of the plants you'll see in the desert are species of cactus. You might come across yucca, aloe, octillo plants, or the tall saguaro cacti. A few animals—mainly reptiles, like snakes and lizards, and amphibians, like frogs and toads—are well adapted to the hot desert. Another famous desert animal is the camel, which can make water from the fat it stores in its hump. The Emperor and Adélie penguins are well-known animals living at the edge of the Antarctic desert.
Grasslands are places with hot, dry climates that are perfect for growing food. They are known throughout the world by different names. In the U.S. they are called prairies and extend from the Midwest to the Rocky Mountains. In South Africa, grasslands are called the veld. Hot, tropical grasslands called savannas are found in South America and Africa. In Eurasia, temperate zone grasslands are called steppes; in South America, pampas.
This inland biome is made of vast areas of grassy field. It receives so little rain that very few trees can grow. The U.S. prairies are used to graze cattle and to raise cereal crops. There is little variety of animal life. Some original prairie animals like the wolf and bison have come close to being eliminated from the habitat by hunters. Today, some of the most common grassland animals include the prairie dog and the mule deer in North America, the giraffe and the zebra in Africa, and the lion in Africa and Asia.
Mountains exist on all the continents of the earth. Many of the world's mountains lie in two great belts. The Circum-Pacific chain, often called the Ring of Fire, runs from the west coast of the Americas through New Zealand and Australia and up through the Philippines to Japan. The other major belt, called the Alpine-Himalayan, or Tethyan, system, stretches from the Pyrenees in Spain and France through the Alps and on to the Himalayas before ending in Indonesia.
Mountains are usually found in groups called chains or ranges, although some stand alone. A mountain biome is very cold and windy. The higher the mountain, the colder and windier the environment. There is also less oxygen at high elevations.
The animals of this biome have adapted to the cold, the lack of oxygen, and the rugged landscape. They include the mountain goat, ibex (wild goat), sheep, mountain lion, puma, and yak. All of them are excellent climbers, which means they can move freely in the steep, rocky landscape. Types of plants vary depending on geographic location and altitude. Lower elevations are commonly covered by forests, while very high elevations are usually treeless.
Tropical rainforests are found in Asia, Africa, South America, Central America, and on many of the Pacific islands. They are often found along the equator. Almost half of the world's tropical rainforests are in the South American country Brazil.
There are other types of rainforests around the world, too. For example, northern Australia has a “dry rainforest” that experiences a dry season each year, and the rainy Pacific Northwest in the United States has a “temperate rainforest” that is made up of evergreen trees.
Tropical rainforests receive at least 70 inches of rain each year and have more species of plants and animals than any other biome. Many of the plants used in medicine can only be found in tropical rainforests. The combination of heat and moisture makes this biome the perfect environment for more than 15 million plants and animals. The thick vegetation absorbs moisture, which then evaporates and completes the cycle by falling again as rain.
A rainforest grows in three levels. The canopy, or tallest level, has trees between 100 and 200 feet tall. They block most of the sunlight from the levels below. The second level, or understory, contains a mix of small trees, vines, and palms as well as shrubs and ferns. The third and lowest level is the forest floor, where herbs, mosses, and fungi grow.
Rainforests are an endangered biome. People have cut the trees and sold the wood for firewood, building materials, and paper. Parts of the rainforest have been burned to make space for grazing and farming. Every minute, approximately 30 acres of rainforest are destroyed. The large amounts of carbon dioxide that are released due to the cutting and burning of rainforests contribute to the greenhouse effect.
Some of the animals of the tropical rainforest are the anteater, jaguar, brocket deer, lemur, orangutan, marmoset, macaw, parrot, sloth, and toucan. Among the many plant species are bamboo, banana trees, rubber trees, and cassava.
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