Predators affect all aspects of their environment

I just found this article, although its a few months old now, on the Beeb:

http://www.bbc.com/future/story/20140128-how-wolves-saved-a-famous-park

I knew that the reintroduction and protection of wolves in Yellowstone had a beneficial impact on the elk and buffalo populations, but this is the first time I learned that this cascaded into a healthier environment overall.   Because the predatory pressure on the elk was previously removed, their numbers expanded to the point where the land couldn't sustain them without detrimental impact.  By reintroducing wolves into the equation, the elk both lost numbers and had to modify their behavior; this allowed the overgrazed trees to bounce back to a health level.

Everything has an impact.