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发表于 2010-12-29 01:16:37
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本帖最后由 ihuazi 于 2010-12-29 01:22 编辑
Argu 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 population is the result of deer being unable to follow their age-old migration patterns across the frozen sea."
In this argument the author concludes 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. To support this conclusion the author cites several facts:(1)Reports from local hunters show that deer populations are decline.(2)Recent global warming trends have caused the sea ice to melt at the same period.(3)The deer search for food by moving over ice from island to island during the course of a year. Even if the author's reasoning seem to be attractive, we may still perceive that this argument rests on a series of unconfirmed assumptions, and is therefore unconvincing as it stands.
Firstly, there is no evidence indicating that reports given by local hunters are reliable. It is possible that the number of hunters investigated is very small, which renders the result of the reports unconvincing. Moreover, it is entirely probable that the survey of the reports from the hunters is based on their empirical experience, but not scientific statistics, thus the results of the results are suspicious. It is possible that the population of arctic deer is not declining, but keeping stable, or even increasing.
Secondly, the global warming trend does not indicate that Canada's arctic region also undergoes a warming process. Moreover, even assuming that Canada's arctic region is undergoing a warming process, there is still no evidence showing that the sea ice in Canada's arctic region is melting. It is possible that the temperature in this region is still low enough to sustain the sea ice solid, thus the migration patterns of arctic deer are not changed.
Finally, even assuming that the number of arctic deer is decreasing, and the climate in Canada’s arctic region is also becoming warm, we still cannot simply attribute the decline of arctic population to the disturbance to migration patterns of arctic deer. There are many factors that may render the decline of arctic deer population, such as excessive hunting, epidemics and destruction to the environment they live in.
To sum up, the reports from the hunters are unreliable, and the warming process in Canada’s arctic region is lack of evidence. The decline of arctic deer population cannot be simply attributed to the disturbance to the migration patterns of arctic deer. In order to improve the argument the arguer should provide more evidence to show that other factors have little influence on arctic deer population. |
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