A、Because salmon live in the streams near the banks. B、Because the banks help prevent erosion of the soil. C、Because the banks c

Today we continue our series on ecology and conservation with a look at a particularly endangered member of the black bear family. One in ten black bears is actually born with a white coat, which is the result of a special gene that surfaces in a few. Local people have named it "the spirit bear". And according to the legends of these communities, its snowy fur brings with it a special power. Because of this, it has always been highly regarded by local people—so much that they do not speak of seeing it to anyone else. It is their way of protecting it when the strangers visit the area.
    The white bear’s habitat is quite interesting. The bear’s strong relationship with the old-growth rainforest is a complex one. The white bear relies on the huge centuries-old trees in the forest in many ways. For example, the old-growth trees have extremely long roots that help prevent erosion of the soil along the banks of the many fish streams. Keeping these banks intact is important because these streams are home to salmon, which are the bear’s main food source. In return, the bear’s feeding habits nurture the forest. As the bears eat salmon, they discard the skin and bone in great amounts on the forest floor, which provide vital nutrients. These produce vegetation that sustains thousands of other types of life forms, from birds to insects and more.
    Today, the spirit bear lives off the coast of the province of British Columbia on a few islands. There is great concern for their survival since it is estimated that less than two hundred of these white bears remain. The best way to protect them is to make every effort to preserve the delicate balance of their forest environment—in other words, their ecosystem.
    The greatest threat to the bear’s existence is the loss of its habitat. Over many years, logging companies have stripped the land by cutting down a large number of trees. In addition, they have built roads which have fractured the areas where the bear usually feeds, and many resting sites have also been lost. The logging of the trees along the streams has damaged the places where the bears fish. To make matters worse, the number of salmon in those streams is declining because there is no legal limit on fishing at the moment.
16. What makes "the spirit bear" look special?
17. What do local people do to protect "the spirit bear" from strangers?
18. Why is keeping banks intact important for bears?
19. What is the biggest threat to the bear?