TPO 23

The lecture and the reading passage discuss possible reasons for declining the yellow cedar trees. Although the passage claims that scientists have several hypotheses that explain this phenomenon, the speaker refutes this idea for several reasons, which I will describe in this report.

First, the passage points out that insects especially beetles were attacked by the yellow cedar trees, and they would be damaged to the trees and killed. The lecturer, in contrast, rejects this by claiming that the healthy yellow cedar can produce saturate powerful liquid that kills the insects because this liquid is poisoning for insects. But, if the tree is not healthy, it would not produce poisoning liquid and defend itself. Thus, the yellow cedar tree would be damaged before the attack of the beetle.

Furthermore, the passage states that brown bears claw trees because trees have sugar liquid which bears eat as food, so damaging the yellow cedar trees would kill them. However, the professor believes that cedar trees were declining overall such as the islands and Mainland. In the islands beers were not living, but the cedar was declining. So, with and without bears yellow cedar trees were declined. Hence, bears cannot main reasons.

Finally, although the reading passage says that gradual changes in climate may be the cause of this reduction, the professor disagrees by mentioning that more yellow cedar trees are dying in lower elevations that have a warmer climate than the higher elevation. Thus this declining pattern counters the hypotheses of climate change role in yellow cedars' population decrease.