سؤال قراءة ستيب محلول — فهم التفاصيل (تدريب 7983)

1) There were once many Wolves in Yellowstone National Park, but by 1926, humans had hunted them to extinction there. The absence of wolves affected many parts of the Yellowstone ecosystem. 2) Most significantly, the disappearance of wolves led to a huge increase in the number of elk (a type of deer). This in term had negative effects on plants and animals in the park. Park authorities tried to keep the elk population under control by hunting, but in the late 1960s and 1970s, the U.S government and the park managers began considering a new policy. They wanted to return to natural processes for regulating the balance of wildlife in the park. 3) In 1995, Congress authorized reintroducing the gray wolf to Yellowstone. The first wolves were brought in from Canada a year later. Almost immediately. Authorities noticed differences in the park. As a result of the reintroduction of wolves, the number of elk declined. This led to an unexpected change. The number of willow trees and aspen, which elk eat. increased. Beavers, which feed on willows, in tum grew more numerous. In addition, the populations of some songbird species and small mammals that live in aspen stands have since grown. Other animals and people have benefited, too. Scavengers, or animals that eat dead animals, have increased in number.