We've been having a great discussion on Scylla's post on BackTalk about the resurgence of fishers, and it reminded me of the reintroduction of wolves to Yellowstone Park, which I mentioned in one of my comments, but I thought it deserved a bit more coverage, so here's a separate post on the wolves.
By the early 1990's Yellowstone Park was pretty much dying; the trees were dying, and because the trees were dying the birds were leaving, the rivers were drying up, shrubs and other plants were dying too. It was becoming a wasteland. The only thing that seemed to be thriving were the herds of elk. Then, in 1995 66 wolves from Alberta were moved into Yellowstone Park. The short film here describes what happened then. They identify the problem as deer, and don't mention elk, but I think that's a minor point.