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TOPIC: 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."

WORDS: 545          TIME: 00:40:00          DATE: 2010/7/26 21:46:56

In this letter, the author asserts that global pollution of water and air results in the sharp decline of amphibians worldwide. To make his argument more specific, the arguer notes statistical information in two studies in Yosemite National Park, which accordingly proves the author's conclusion. The author also prudently argues that import of trout is not closely relative to the decline of amphibians. The argument is convincing on the surface, while several critical flaws weaken  the author's line of reasoning.

In the first place, the validity of the two studies is oppugning. As concrete information with respect to whom these studies are conducted by, and the research condition such as weather and the temperature, is not presented in this argument, accordingly the result is not so reliable as to be the support of this argument.

Moreover, even if the studies are reliable, the author is assertive to get the conclusion merely based on the fact that three species of amphibians have been extinct during a period of 77 years. It is actually possible that due to earthquakes, floods, tornados and other natural disasters happened in the past, which devastatingly destroyed the whole park, during which the amphibians, as only one species of the biosphere, inevitably suffered from this calamity. Since the argument is lack of evidence to show that no disasters took place in the past few decades, we cannot imprudently draw the conclusion that a drastically decline in the numbers of amphibians is caused by human beings, other than the nature itself.

In the second place, barely from this argument we cannot vouch the inference that introduction of trout should not be the principal reason for the decline of numbers of amphibians. Given that influence of trout in Yosemite is not representative enough, good chances can be that trout are extensively distributed so that most trout perches where amphibians are multitudinous, on account that, as mentioned in the passage, trout are known to eat amphibian eggs. Therefore, unless the author provides evidence showing few trout are in the same habitat with amphibians worldwide, we cannot be convinced that no link is constructed between the existence of trout and the number of amphibians.

A third problem, which is identified to be the most severe one, is that we are told nothing about how serious the water and air pollution affects the quantity of amphibians, in consequence, it is dubious that these kinds of pollution is the culprit rather than other kinds of pollutions. In spite of that, global climate change, damage to O-zone layer can as well influence the number of amphibians. To further convince the readers of the influence of air and water pollution, the author should identify specifically how air and water pollution impose detrimental influence on amphibians and should also effectively exclude other factors possible to affect the number of amphibians.

In conclusion, the author's argument is unconvincing as it stands. To strengthen the argument, the author must prove the validity of the studies. Additional evidence of the studies such as whether there are disasters during the past and the correlation between trout and amphibians worldwide is also necessities to make this argument more convincing. Furthermore, the author should preclude other factors such as global warming to make the conclusion more convictive.