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45.The following appeared as an editorial in a wildlife journal.

"Arctic deer live on islands in Canada's arctic region. They search for food by moving over ice from island to island during the course of a year. Their habitat is limited to areas warm enough to sustain the plants on which they feed, and cold enough, at least some of the year, for the ice to cover the sea separating the islands, allowing the deer to travel over it. Unfortunately, according to reports from local hunters, the deer populations are declining. Since these reports coincide with recent global warming trends that have caused the sea ice to melt, we can conclude that the decline in arctic deer populations is the result of deer being unable to follow their age-old migration patterns across the frozen sea."



In this argument, the author claims that the decline in arctic deer population is the result of deer being unable to follow their age-old migration patterns across the frozen sea. To bolster this assertion the author notes that this decline coincides with recent global warming which leads to the sea ice to melt. Nevertheless, after further consideration in details, I find this argument logically unconvincing in three respects.

First of all, the author fails to provide any information available to justify any causal relationship between the deer's numbers decline and the global warming trend. In older to prove the latter is contributable to the former, the author must exclude other possibilities. Perhaps human being's some certain activities, like over hunting， cause more deer to die. Or perhaps, in recent years, there are more natural disasters or terrible disasters have an effect on the deer's number. Unless the author precludes all these possibilities, this argument is ill-founded.

In addition, we should not put the responsibility of lacking food on the head of the global warming trend. On the one hand, there is no sound evidence to prove that the temperature is increasing to the degree to melt the ice. What if the temperature just has a very tiny change? On the other hand, even if the temperature dose rises to a very high level, it is possible that the high temperature stimulate some other plants to grow, and the deer would also prefer such kind of food. Without ruling out all these factors, the author's assertion would be questioned once again.

Last but not least, the author cites that the deer's population is declining according to local hunters. This survey is so unconvincing because we must consider how the survey is conducted. It is essential to ensure a large sample size to grantee a relative better availability of the survey. Moreover, we must consider if the hunters are representative and forthright enough to provide authentic and believable answer out of consideration for their privacy. Perhaps they are so afraid of the government to limit their hunting activity because too much deer is killed that they lied about the real number of deer.

To sum up, this assertion lacks credibility due to the fact that the evidence cited in the argument dose not lend powerful support to what the author maintains. To strengthen the argument, the author need provide more detailed information about the survey and other factors to cause deer’s decline.