【Flyer杀G作文组】2月20-21日作业ARGUMENT150-yuqi

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题目：ARGUMENT150 - The following is a letter to the editor of an environmental magazine.

"The decline in the numbers of amphibians worldwide clearly indicates the global pollution of water and air. Two studies of amphibians in Yosemite National Park in California confirm my conclusion. In 1915 there were seven species of amphibians in the park, and there were abundant numbers of each species. However, in 1992 there were only four species of amphibians observed in the park, and the numbers of each species were drastically reduced. The decline in Yosemite has been blamed on the introduction of trout into the park's waters, which began in 1920 (trout are known to eat amphibian eggs). But the introduction of trout cannot be the real reason for the Yosemite decline because it does not explain the worldwide decline."
字数：325
用时：00:30:00
日期：2011-2-22 9:07:47

The argument is well-formed, but not well-reasoned. The author suggests that the decline of amphibians world wildly is caused by the global pollution of water and air. To support his suggestion he cites two studies of amphibians in Yosemite National Park (YNP). Through careful analysis, I find several logical fallacied in the argument.

First, the authors fails to provide statistics on the number of global numbers of amphibians, so whether the worldwide decline really happened or it is just a deduction of the author. There is one possibility that the decline of amphibians in YNP is just a single case because of, such as, the local climate change or industry pollution, while in other places amphibians reserve well protection and the number is stead.

Second, some deeper inspections should be conducted in the two studies in YNP. There are maybe some other explanations on the decrease of amphibians in YNP. During nearly 80 years, the local climate of YNP may have changed, which leads to the migration of amphibians to other habitates. The temperature of YNP may rise so that it is not proper to some certain species any more. YNP may also influenced by too many tourists and human tracks damage the nature environment, thus some amphibians no longer live there. What's more, the introduction of trout probably is responsible to the decline of amphibians. Trout are known to eat amphibian eggs, which is deadly to amphibians. Therefore, the studies should investigate more to rule out other possiblities and get the final cause.

Third, even the global decrease of amphibians is true, is it really due to the pollution of water and air? As no information related to water and air pollution is provided in the argument, we can easily think up some other causes, such as the global warming which change the environment worldwildely, the overly interference of human in nature which destruct the nature balance everywhere, ect. So, there many other reasons.