TPO23-Integrated writing

The article states three hypothesis explain the decline the population of the yellow cedar and provides three reasons of supports. However, the professor says that unfortunately we still do not know the cause of this decline and refutes each of the author’s supports.

First, the passage explains that the yellow cedar decline may be caused by insect parasites like the cedar bark beetle. The lecture refutes this point by explaining that the cedar bark beetle is not the fundamental cause responsible for the decline of the yellow cedar. The healthy yellow cedar is much more resistance to this kind of parasites than other trees species, since the bark and the leaves of yellow cedar trees are saturated with chemicals that are poisonous to insects and causes their death, so the healthy yellow cedar trees are unlikely to suffer from insect’s damage. Moreover, the explanation of those dead cedar there infested with beetles; the beetles were attacked yellow cedar trees that already damaged or sick.

Second, the article posits that the aggressive feeding habits of brown bears attribute the decline of the yellow cedar population. In contrast, the professor says that brown bears are not the cause of the overall population decline. He mentions that there are also declines in the population of the trees across the northwestern coast of the North America, in the mainland and the Island, although there are no bears in the Island. The cedar’s decline with or without the presence of brown bears.

Third, the author explains that the gradual changes of climate in northwestern North America may count as a reason for the decline of the trees since it causes damage to the rooting system and the damage to the cedar trees will be more in the cold climate rather than in the warm climate. The professor refutes this point by explaining that there are more damaged trees at low elevation in warmer climate rather than in high elevation at cold climate. Hence, the high elevation may cause the cedar roots to be more sensitive to cold but not responsible for their damage.