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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."
F1:当地猎人的观察不一定可信,鹿群可能已经迁徙至其他地区
F2:并没有证据表明当地气温升高或冰块已经融化,全球趋势并不能推断局部情况
F3:鹿群数量减少可能由于其他原因造成——狼、熊等天敌增多,植被破坏导致食物减少,出现其他物种争夺食物,流行病等
Text:
The editor of this article tries to convince us that the decline of the number of arctic deer is due to recent global warming trends, and the evidence he provided is no more than some reports from local hunters. Via a close scrutiny over his standpoints, several hasty assumptions and illogical reasoning processes can be easily detected, rendering his article hardly persuasive.
To start with, the only evidence, reports from local hunters, turns out to be quite unwarranted in that the hunter's active range, especially in arctic areas, is rather limited compared to any wild animal. They can only generate data when they are out for hunting, thus their reports are actually based on some random observations, lacking decent credibility. Moreover, the arctic region in north Canada is so vast that much of its territory remains desolated. Given that the arctic deer is a species with a migrating habit, it's highly possible that the herds have already moved to some other islands affluent in food, which was not witnessed by local hunters.
Secondly, granted that the deer population is indeed declining, this phenomenon cannot be rashly attributed to the recent global warming trends, since the worldwide trends may not be accurate in describing the climate change in a specific area. It’s entirely possible that the local temperature levels off in recent years or has got even lower. If the author fails to provide any detailed local weather statistics to buttress his contention, he would have committed the fallacy of a false analogy. Even assuming the temperature has escalated, there’s no solid evidence showing that the ice among local islands would be bound to melt, let alone barricading the process of deer’s migration.
What's more, the editor doesn't rule out other possibilities may cause the same consequences. Perhaps the natural enemies of the deer, such as wolves and bears, boosted their populations in recent years, constituting a major menace towards the deer’s existence. Or perhaps the human activities there have severely devastated the green vegetation served as a primary food resource for them. Or there's another immigrant species which shares the same forage with deer yet more aggressive, leaving little living space for the deer. Moreover, there could be a vital infective plague among arctic deer, reducing its populations sharply.
To sum up, the evidences and conclusion given by the author were generally not compelling. To back his points, a more authentic observing report on deer's population is badly demanded, yet some elaborate researches in order to eliminate the possibility of other theories should also be conducted. Only by this way can the editor be quite confidence about his contention on the decline of arctic deer.
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