"In Yellowstone National Park, Warming Has Brought Rapid Changes"
"YELLOWSTONE NATIONAL PARK — On a recent fall afternoon in the Lamar Valley, visitors watched a wolf pack lope along a thinly forested riverbank, ten or so black and gray figures shadowy against the snow. A little farther along the road, a herd of bison swung their great heads as they rooted for food in the sagebrush steppe, their deep rumbles clear in the quiet, cold air."