TPO-23 - Integrated Writing Task 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 expla

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There is a consent with fact that the populational of the yellow cedar is decreasing. However, the lecturer does not think that the hypotheses presented in the passage to explain this decline are adequate, and this essay will counter their arguments.
According to the author, the first possible reason for this event are the existence of insect parasites, to be more specific, the cedar bark beetle, which attack and kill these trees. On the other hand, the lecturer mentions the fact that the healthy yellow cedar trees are more resistant to infestations if compared to other trees, which makes insect damage unlikely, not forgetting to mention that parasites target are sick trees, which denies this hypothesis as the fundamental cause for yellow cedar decline.
The second hypothesis cited in the passage is related to the presence of brown bears. It is known that yellow cedar trees have a big amount of sugar on their barks and brown bears, intending feed themselves, tends to use their claws in order to seek for sugar, which destroying the trees. Nevertheless, the lecturer highlights the fact that the northwestern coast of U.S. area does not have bears, and the population of yellow cedar trees – with or without bears – are still declining, so bears could not be considered as a response.
As last, the third hypothesis stated by the author in the reading passage indicates the climate change as a possible reason for the yellow cedar decline. With the past of time, seasonal patterns have been currently changing, and the temperature between seasons made the growing roots more sensitive than before, and, consequently, less resistant and easily damageable by the cold. In opposition, the lecturer noticed that yellow cedar trees are present as in lower elevation areas, which temperature are usually hotter, as in higher elevation areas, which temperature are cold and, theoretically, more harmful for these trees. In instead, the lecturer highlights that more trees are dying in relatively lower elevations, which means that this hypothesis is also not what is killing them.

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