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43. North America's Rainforest 北美雨林

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When people think of rainforests, they usually think of the tropical jungle. But heavy rain can also produce dense forests in temperate areas. Along the northwest coast of North America, there are some of the largest trees in the world. This forest runs along the Pacific Coast from Alaska down to northern California. About half of it is in British Columbia, Canada. Several species of trees grow to an immense size. Some grow up to 95 metres (312 feet) high, and 12 metres (40 feet) in circumference. They may be as much as 1,000 years old. Because the trees are so tall, the forest has various levels of growth. Small plants attach themselves to the tall trees and may form a kind of garden in the air. Further down are the tops of the younger trees. Closer to the ground are shrubs and bushes. Along the ground are moss, ferns, berries and other plants. These old forests have developed over several thousand years. The tall trees are at least several hundred years old. This old forest has several special features. Some of the dead tall trees remain standing and become homes for insects, birds and small animals. Trees that fall to the ground can become "nurse logs" for new plants or trees to grow on. Trees that fall across rivers and streams can provide natural dams, which provide quiet water for animals to live in. In recent years, it has become common for logging companies to "clear-cut" this old forest. To clear-cut a forest means to go into a section of forest with heavy machinery and cut down every tree. Sometimes, these "clear-cuts" are as large as some European countries. Logging companies are doing this because it is a cheap method of logging. The problem is that when an old forest is cut, it does not grow back again. Even with replanting, companies produce a tree farm, not an old forest. The complexity of an old forest, which grew over thousands of years, is lost forever. The old forest can shelter many kinds of birds, mammals, fish and plants that a replanted forest cannot. Another issue is that companies are cutting more and more old forests because they haven't done enough replanting. As long as governments have been willing to let companies cut old forests, neither logging companies nor governments have been much motivated to replant the forests. As a result, most of the old forest has been cut down and continues to be cut at a rapid rate. This situation has also worsened because new technology allows more rapid logging. Clear-cut logging results in erosion, which, in turn, damages the quality of rivers and streams. This causes a decline in the salmon fishery. Animals like grizzly bears, elk and deer are harmed by the loss of habitat. Likewise, birds that nest in the old forest, such as bald eagles, owls, woodpeckers and various seabirds are being threatened. Recently, public interest in the old rainforests has resulted in an increase in tourism. People come to see these spectacular trees and the many plants and animals that depend on them. We hope that these unique temperate rainforests will remain for many more generations to enjoy.

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