Wolves are a very necessary and vital link in a natural ecosystem.
The common belief most of us have is that wild wolves' best and only attribute is killing things. And to a minor extent that is true. They are, however, good for so much more, including creating bird habitat. It's shown in this YouTube video shot at Yellowstone Park by Sustainable Man;
... OR (if the video is temporarily unavailable)
search in YouTube using 'wolves Yellowstone sustainable'