Yellowstone Wolves
Need Help From Beavers
To find out whether wolves could rescue the willows, Marshall and her colleagues charted willow growth at four sites in the northern range. At each site, the researchers fenced some plots to provide total protection from browsing elk and other animals. They also built dams—hauling in logs by helicopter—in streams near some plots to mimic the effect of beavers. Some plots were dammed and fenced; control plots were neither dammed nor fenced, making wild wolves their only possible protection from elk.
After 10 years, the fenced willows that weren’t close to dams, though they’d suffered no browsing at all, on average were far shorter than 2 meters, the team reports online today in Proceedings of the Royal Society B: Biological Sciences. That’s the threshold height that makes willows tall enough to reproduce despite voracious elk. Unfenced willows along dammed streams didn’t make the threshold either. Only a combination of dams and fences provided the right conditions for the willows to grow to a self-sustaining height.
Another fine study shows [basically] that man cannot reinvent the wheel without beavers in the mix. Who would have thought? So wolves are important to the recovery of yellowstone but can’t do their magic unless beavers do theirs. Hmm. And pretend dams are interesting opportunities to carry logs by helicopter but beavers make the ones that really matter. Are you shocked?
If beavers need willows, willows also need beavers. Beaver dams help create mud flats where new willows can sprout; they also raise the water table, supplying more water to willow roots. When wolves vanished, the willows of the northern range faced a double whammy: too many elk, too few beaver. The result was a scarcity of the thick, lush willow patches needed for a healthy riparian zone.
Wait a minute. Maybe its not just wolves that need beavers to plant the trees that feed the elk that they harvest. Maybe its all of us! Didja think of that?
All agree, however, that beavers might help the willows and riparian zones make a comeback. But until willows are vigorous, beavers could starve. It’s hard to see a way out of this “chicken-and-egg” problem, Marshall says. Perhaps if Yellowstone got a very wet year, encouraging willow growth, combined with a year that saw a low level of elk browsing, beavers could establish a foothold in the small streams of the northern range, as they have in other parts of the park. “It’s feasible that it could happen on its own,” she says. “It’s just not likely in the next few years.”
I’ll tell you what. Instead of using those tax and grant dollars to carry logs and measure trees, why don’t you sponsor a pizza party for every boyscout in the state and involve them in planting stakes of willow as far along the waterline as you and the wolves can see. Then when the sprouts burst along the riverside beavers will settle in and have enough to eat and your problem will be solved.
