CORVALLIS, Ore. — Yellowstone streams recovering thanks to wolf reintroduction.

After decades of erosion, streams in Yellowstone National Park are recovering. According to a study by Oregon State University scientists, it's thanks to the wolves that were reintroduced into the area in the mid-90s.

OSU Ecology professor Bill Ripple said what he and his colleague Robert Beschta discovered was both exciting and humbling.

The researchers looked at stream bank plants and vegetation over a 13-year period starting in 2004.

That's about nine years after the government reintroduced wolves back into Yellowstone. The Yellowstone wolf population had been killed off in the early 1900s. In the decades following, elk populations exploded, and those elk ended up eating so much of plants along the streams their banks eroded, and the streams suffered.

The scientists found, when the wolves returned, they helped to naturally reduce elk populations. Fewer elk meant the plants along the streams could grow.

And as all those plants grew, the stream banks stabilized, erosion stopped, and the overall health of the waterways greatly improved.

Birds and other wildlife returned, as did insects, which increased fish populations and so on.

"I guess the bottom line is that this Yellowstone mystery can be solved with wolves and other predators as being the key to maintaining a healthy ecosystem," Ripple said.