Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 43 to 50.
Tropical rainforests are being destroyed and badly degraded at an unsustainable rate. Some scientists estimate that in the early 1990s tropical forests were being destroyed at a rate of approximately 28 hectares a minute, or about 14 million hectares each year – an area about the size of the state of Wisconsin. This figure marked a decrease since the 1980s, when approximately 16 million hectares were destroyed each year, largely due to a reported decline of deforestation in the Amazon River Basin in the early 1990s. However, satellite images indicate that rates may have rebounded in the late 1990s as burning in the Amazon increased again. Over the past three decades alone, about 5 million square kilometers – or 20 percent of the world's tropical forests – have been cleared. During this time, deforestation in tropical Asia reached almost 30 percent. High rates of deforestation are inevitably followed by alarming rates of plant and animal extinction because many rainforest species cannot survive outside their pristine rainforest habitat. Some scientists estimate that dozens of rainforest species are becoming extinct every day.
Causes of deforestation vary from location to location, but certain patterns tend to be consistent across all forests. Logging companies in search of valuable rainforest hardwoods, or, less often, oil companies in search of petroleum, are often the first to enter a remote area of rainforest. Some logged forests, if left alone, can regenerate in a few decades. But typically, they are not left alone – the roads built by logging companies often provide access for landless farmers to enter a new area, as well as a means to transport agricultural crops to market. For every 1 kilometer of new roads built through a forested area, 4 to 24 square kilometers are deforested and colonized.
Once the loggers leave the land, a typical cycle of destruction ensues. When the landless farmers arrive, they clear the land for planting. Poor rainforest soils produce a low crop yield, especially after a couple of years. At that point, the farmers often sell their lands to cattle ranchers or large plantation owners. After nutrients have been exhausted and soils compacted by cattle, lands are then abandoned and often laid to waste. Rainforest does not readily regenerate on these lands without human intervention. Meanwhile, the colonist farmers and cattle ranchers move to a new piece of land made accessible by logging roads, where the cycle of deforestation begins again.
(Source: Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation)
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