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发表于 2008-3-20 21:55:45
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45The 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."
The notion 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 seems a reasonable conclusion at first. After all, the arguer cites from local hunters' reports and the coincidence with recent global warming trends. However, the conclusion may mask other factors of the decrease of deer and thus comes to the conclusion in a hasty and improper way.
At the threshold of the argument, the arguer fails to consider other possible factors that might lead to the decline in arctic deer populations. It is cited that the deer declination report coincides with recent global warming trends, which directly makes the arguer attributed the weather to the main cause of the decrease. However, the concurrent relationship cannot be solely categorized into causality. As the case stands, there might be several reasons for the decrease. It is entirely possible that the deer become fewer in respect that the hunters capture the arctic deer more often than before, or the deer have already found the living atmosphere no longer fit for them to live and thus migrate to other islands. Even assuming that the unusual climate has some effect on the deer, there is no evidence that it is related to the reduction of them. Probably the changing weather alters the living space and daily activities of the deer, instead of killing them.
Granted that the warming trends do influence the existence of arctic deer, the authenticity of the decline in deer populations is still open to doubt. It is mentioned in the argument that the conclusion is drawn from the local hunters. However, without detail information about the report, it is questionable that the report is comprehensive or authentic. Perhaps the hunters' skills are not qualified enough and hence cannot hunt the deer as much as possible; or the hunters search arctic deer only in a small range that the existence of deer is approximately at low rate. It appears reasonable, therefore, for the arguer to focus on these elements rather than blindly regarding the report as the only clue to deduction.
Last but not least, the arguer fails to exclude the feasibility that the arctic could travel across the frozen sea. No supportive evidence is shown that the reason why arctic deer migrate is only due to their age-old pattern. As is referred, they move over ice to search food from island to island, however, it does not necessary mean that they move mostly for food. Actually, they may move across the ice to find their companies, or to take a rest. Without ruling out these probabilities, the arguer's assumption is still problematic.
Consequently, the reasoning behind the declination of arctic deer seems logical as described above since the warming trends affected deer's lives and they cannot follow their original migration pattern. Nevertheless, before any cause comes to the reduction of the deer, the arguer should take into account for other possible reasons leading to the declination, reevaluate the report from hunters, and estimate some potential ingredients for their migration. |
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