ARGUMENT45 - 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."
The arguer provides an assertion that the decline of the arctic deer's population is because the deer cannot migrate across the frozen sea.
His conclusion derives from three reasons: local hunters report fewer deer; global warming treads makes the sea ice to melt; the deer have the habituate of moving over ice from island to island. At first glance, the argumentation is quite sound. Yet after comprehensively reflection, there are several flaws in it.
First of all, whether the deer population is declining is quite susceptible. The speaker just provides the local hunters' report to support this statement. However, it is possible that the deer become more alert to hunters. It also might that the deer's activity region is difference from the hunters'. In these cases, the conclusion that the Arctic deer are disappearing is groundless.
Secondly, if the decline of the deer's population is acceptable, we can not asserts this trend results from the influence of global warming.
There are many other factors that can affect the deer's population. For instance, the number of deer hunters might increase.
Or the hunters might slaughter more deer than ever before. The author fails to consider these aspects and exclude their effect. On the other hand, admittedly, global warming makes temperature rise and the sea ice melt in most places of the world. However, it doesn't mean that the habitat of the deer endures the harm of the global warming. It is likely that the temperature of that region is low in recent years while other places have warm weather. In the meantime, the author does not afford us any information about the weather condition of that region in this argument.
Thirdly, if we suppose that the population decline is mainly the affection of global warming, the speaker can not arbitrarily say that because of global warming, deer are unable to migrate. Perhaps that global warming does not lead all the sea ices in that region melt, and the way of the deer’s migration might not be blocked. However, it is probable that the raise of the temperature might make the plants which the deer depend on wither. Without foods, the deer population would surely decrease. In short, the outcome of global warming on Arctic deer should be revalued.
In sum, to strength the conclusion, the author should offer more details about the weather conditions in that region. And he should also do more research on the surviving condition of the Arctic deer.