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每一次的A都很艰难,sorry for the delay~
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."
outline:
1.Is the number really declining?
2.even 1+ no evidence to support global warming have caused the declining(the ice here may not meld or meld to the level can prevent Arctic deer from migration, other good effects)
3.Arctic deer's declining might due to other reasons(hunters, other species, food)
In this argument, the author is meant to research on the cause of Arctic deer's declination. However, the declaration of declining is just based on survey of a minority of people. In addition, the process of concluding only scratched the surface of coincide scenario, global warming, and also ignored several other possibilities.
First, before doing research on dynamics of deer population, the question, whether the number of deer really declines, should be investigated thoroughly. Let's take a look at the survey offered above. Merely mentioning the vague words---"local hunters", the author didn't provide the exact numbers of these people, and other information, such as their living area and active hours of the day. It is entirely possible the survey was done on the migrating season, when the deer living in the same island with these hunters have been traveling to other islands; or the hunters just hunter in the migrating season when the deer are more active, yet was asked about the question in the other time. Besides, if hunting deer is an illegal action, to avoid being punished, these guys might claim the number is declining so that we haven't hunted for anything. Without more detailed information, the declining of deer population remains a specious assertion.
Even if the declining exists, just resting on the coincidence of global warming, the author's conclusion is unsound. The habitat of these deer is a polar place where temperature is extremely low. Hence the global warming trend may not rise the temperature here above zero, though it do cause the sea ice to melt in a general scope. Just admit this assumption is valid, there can also be other consequence resulted from global warming, say, the plants which the deer feed on grow more prosperously, thus the deer may not need to travel across island to search for food.
Finally, there are alterative explanations which may have influence on the living environment of the deer. The most obvious one is mentioned by the author but than ignored, yes, it is the activity of hunting, which may be majorly contributive to the death of deer than other natural force. Besides, are there any factors that caused the death of the plants these deer feeding on recently, such as the plant disease or the unadaption to temperature change? Are there new predators of deer introduced to this area? And there is also lack evidence to prove the deer will die without their old migrating living pattern.
In sum, though the intention of the author and his effects should be recognized, they may not be effective. A more scrupulous researcher would investigate all the possibilities discussed above in order to find the most conductive reason why the possible declining happened. Only in this way can he/she take the right action to save the Arctic deer. |