Reading：Populations of the yellow cedar

The reading states the causes of the yellow cedar decline and provides three reasons of support. However, the professor explains that none of these explanations are adequate for the reduction of these trees and refutes of the author's claims.

First, the article claims that the yellow cedar has declined because of insect parasites. Moreover, the author points out that the bark beetle is the specie responsible for the reduction of these trees because it has been reported before to eat wood from the yellow cedar. The professor refutes this point by saying that healthy cedars contain a potential chemical capable to destroy any foreign animals. Moreover, the beetle only attacks trees are already damaged. Thus, this animal cannot be the main cause of cedar reduction.

Second, the reading posits that brown bears have provoked the decline of the yellow cedar. Furthermore, it is explained that bears like to eat the tree barks, which has a high content of sugar making it appealing to the bears. The author states that the aggressive feeding habits of the brown bears are causing the decrease number of cedar to decrease greatly. However, the professor says that the bears do not cause the overall reduction of trees. Furthermore, the speaker points out that the trees have diminished in the island as well where no bears are present. Hence, the bears are not the principal problem.

Third, the article says that the gradual change of climate has caused the trees to nearly disappear. In addition, the writer says that pattern of seasonal as well as day to day temperature changes have affected the root of the trees making it more sensitive to freeze. The professor opposes to this point by explaining that the trees in low elevation where the temperature is warmer are affected more than in the high elevation. Thus, the climate changes cannot be associated with the overall declining of the cedar trees. Perhaps, the cold has made sensible the root, but it does not kill the trees.