TOEFL Integrated Writing Practice Test 043Cedar Tree

Populations of the yellow cedar, a tree species native to northwestern North America, have been declining steadily since around 1880. Several hypotheses have been proposed to explain this phenomenon.

One hypothesis suggests that the decline may be due to insect parasites, specifically the cedar bark beetle. The beetle larvae feed on the wood of cedar trees, and there are documented cases of sustained beetle attacks leading to the death of yellow cedars. This makes the beetle a plausible candidate for causing the trees’ decline.

Another hypothesis attributes the decline to brown bears. These bears sometimes claw at the trees to eat the bark, which contains high levels of sugar, comparable to wild berries, a major part of their diet. Although clawing alone may not destroy the trees, the bears’ aggressive feeding could weaken the trees enough to contribute to the overall decline.

The third hypothesis involves gradual climate change. Over the past century, temperature patterns in northwestern North America have shifted, affecting the yellow cedar’s root systems. The trees’ fine surface roots now grow in late winter instead of early spring, making them vulnerable to freezing on cold nights. This root damage may ultimately compromise the health of the trees, leading to their death.