RBC I Some come for the geysers and grizzlies, but I’ve traveled hundreds of miles to Yellowstone National Park simply to stand in the drainage of Elk Creek, stooped over a stunted willow bush. Tan branches, tinged with red, just reach my thighs, and narrow pale-green leaves blend into the wheat-like stalks of timothy grass and smooth brome filling this humdrum meadow.
Nearby, David Cooper, a Colorado State University ecologist, inspects one willow like a…