The reading passage introduces three proposals that try to explain the decline in the population of the yellow cedar trees.

The reading passage introduces three proposals that try to explain the decline in the population of the yellow cedar trees. However, the speaker in the lecture casts doubt on the hypotheses presented in the article. He believes none of the arguments is adequate. First and foremost, the author holds that the attacks of cedar bark beetles could be the major cause behind the dwindling in the number of trees. In contrast, the lecturer indicates that healthy cedar trees are much more resistant to insects than any other species because the bark and leaves are saturated by chemicals that are poisonous to parasites. Hence, beetles are only capable of attacking the trees that were damaged already. Thus, the invasion by parasites is not the fundamental reason that is endangering this plant. Secondly, the writer contends that the brown bears claw at tree barks and eat them since it contains almost as much sugar as berries which are a staple of the brown bear's diet. As a result, this might have weakened enough trees and resulted in their death. Conversely, the lecturer brings up the fact that the decline is happening both on the mainland where there are bears and on the islands where there are not. Therefore, this process is occurring in the presence and absence of bears and they could not be responsible for it. Lastly, the excerpt argues that climate change made the roots grow in the late winter rather than early spring, which led to partial freezing of the emerging roots. Consequently, the changing temperatures might have played a major role in undermining the trees' growth and further accelerated their killing. Nevertheless, the lecturer refutes this idea by saying that the trees on the lower warmer elevations are more affected than the trees on the higher colder levels. As a consequence, the gradual change in climate is not the root cause that is destroying the trees.