Definitely, a victory 小组第2次作业 Argument45 By3号echo（huohuo0101）

huohuo0101UID: 2760840

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."
逻辑错误：
1作者根据捕猎者的报告就认为北极鹿的数量减少是不严谨的
2 没有证据证明温室效应严重影响了加拿大北极地带，以至于海冰融化，北极鹿无法迁徙
3就算北极鹿数量真的减少，也不能说明就是温室效应造成的。有可能是过度捕猎等其它原因

Author conclude that decline in arctic deer populations is the result of deer being unable to follow their age-old migration patterns across the frozen sea by citing the report of local hunters and associating it with global warming. I find the conclusion logically flawed in many aspects.

    First of all, the author’s assertion that the population of arctic deer is declining is poorly evidenced in spite of reports from local hunters. They may draw their result only from casual observation instead of scientific census. There is great possibility that only the population in particular area where hunters used to hunt declines while populations in other areas remain the same. Lacking reliable statistics drown from rigorously designed investigation, the assertion is not believable.

   Second, the author fail to substantiate the assumption that ice in Canada's arctic region has melt so thoroughly that deer are unable to follow their age-old migration patterns among islands. Although the current common sense states that global warming causes sea ice to melt worldwide, to use it as an evidence to explain a phenomena in a particular situation is far from persuasive. Maybe global warming doesn’t quite affect Canada's arctic region or it just makes the ice layer thinner but still thick enough to hold the flocks going back and forth.

     Third, even declining of arctic deer’s population is an actual fact. The author can’t attribute it to the global warming without ruling out other explanations. Maybe it’s overhunting which may be resulted from increasing demand of fur or other animal products that causes the population to shrink. And also, the change of the food chain may cause the population of arctic deer to decrease. For example ,pollutants change the local soil thus make the grass which arctic deer feed on wither. Or the number of carnivorous animals begin to increase.

    To sum up, the conclusion is based on some unsubstantiated assumptions thus make it unconvincing as it stands. To bolster the conclusion, the author has to substantiate the assumption that the population of the deer is declines by citing convincing evidence. Evidence that ice in Canada's arctic region has melted severely that the islands will be separated permanently also need to be provided. At last, the author has to rule out other explanations of declination of deer population.