TPO 23 – Integrated Writing Task: Populations of the yellow cedar, a species of tree that is common in northwestern North America

TPO 23 – Integrated Writing Task. Populations of the yellow cedar, a species of tree that is common in northwestern North America

“Populations of the yellow cedar, a species of tree that is common in northwestern North America, have been steadily declining for more than a century now, since about 1880. Scientists have advanced several hypotheses explain this decline.

One hypothesis is that the yellow cedar decline may be caused by insect parasites, specifically the cedar bark beetle. This beetle is known to attack cedar trees; the beetle larvae eat the wood. There have been recorded instances of sustained beetle attacks overwhelming and killing yellow cedars, so this insectis a good candidate for the cause of the tree’s decline.

A second hypothesis attributes the decline to brown bears. Bears sometimes claw at the cedars in order to eat the tree bark, which has a high sugar content. In fact, the cedar bark can contain as much sugar as the wild berries that are a staple of the bears’ diet. Although the bears’ clawing is unlikely to destroy trees by itself, their aggressive feeding habits may critically weaken enough trees to be responsible for the decline.

The third hypothesis states that gradual changes of climate may be to blame. Over the last hundred years, the patterns of seasonal as well as day-to-day temperatures have changed in northwestern North America. These changes have affected the root systems of the yellow cedar trees: the fine surface roots now start growing in the late winter rather than in the early spring. The change in the timing of root growth may have significant consequences. Growing roots are sensitive and are therefore likely to suffer damage from partial freezing on cold winter nights. This frozen root damage may be capable of undermining the health of the whole tree, eventually killing it.”

my article：

The reading passage provides three factors that potentially cause the decline of the yellow cedar, while the professor contradicts it by raising doubt about the three factors given by the reading.

As opposed to the writer’s idea, the professor states that the yellow cedar is much more resistance to the insect inspection than other trees. To be more specific, the cedar can release a chemical substance which is toxic to insects such as the beetles. Also, because the beetles attack trees that are already sick or dead, so the claim in the reading that yellow cedar deceases because of insect parasites is unconvincing.

Moreover, the professor continues to discredit the writer’s assertion by arguing that brown bears could not be the reason for cedar decline. In detail, he points that the decrease of cedar happened in both the mainland and island in which bears did not show up. Thus, the statement of the reading seems untenable.

In addition, it is the professor’s third argument that the change of climate could not be blamed for declination. To explore deeper, he contends that more cedars actually died in the lower latitude which is warmer than higher latitude, which is far from the suggestion in the reading passage that the cedars are sensitive to cold weather.