Dieoff Of Whitebark Pines Thx To Beetles May Erase Grizzlies, Unravel Yellowstone Ecosystem - NYT

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The beetle’s usual targets were once midaltitude lodgepole and ponderosa pines. But it has begun extending its range as it adapts to warming temperatures in the Rockies — two degrees since the mid-1970s. As a result, it has been killing whitebark pines at altitudes in the Rockies and the Cascades of Oregon and Washington that would have once been too cold. Beetle attacks have added to the toll taken by a disease called white pine blister rust. In the northern Rockies, the beetle infests 143,000 acres. Entire forest vistas, like that at Avalanche Ridge near Yellowstone National Park’s east gate, are expanses of dead, gray whitebarks.

“We are very worried the whitebarks may be locally extirpated, if not driven extinct,” said Diana Tomback, professor of biology at the University of Colorado, Denver, and president of the Whitebark Pine Ecosystem Foundation, a nonprofit organization. One recent Forest Service study suggested that in the next century a global warming would reduce by 90 percent the acreage that has the kind of cold and high altitude climate where the trees now grow. The plight of trees may not catch the attention of most people. But the seeds of the whitebark pine, the pine nuts, feed Clark’s nutcracker birds; red squirrels, which store the nuts underground; and grizzly bears.

“There is this general notion that grizzly bears are omnivores that will eat anything and do all right, but that’s not the case in Yellowstone,” says David Mattson, a wildlife biologist with the United States Geological Survey on the Northern Arizona University campus in Flagstaff. The diet of the Yellowstone grizzlies changes radically from season to season. After emerging from dens in early spring, they gorge on elk and bison calves and adults that died over the winter, or they chase wolves off their kills. Later in the spring and in early summer, tourists most often see them in rivers near Yellowstone Lake, where they go after spawning cutthroat trout. They eat roots and bulbs, too. But by late summer the bears head for remote high country. They turn to delicate fare: moths and pine nuts. In alpine meadows a grizzly can lap up 40,000 army cutworm moths a day from under rocks where the fat insects congregate during daylight hours.

But mostly the bears depend on whitebark pines. A federally supported Interagency Grizzly Bear Study Team says the tree’s plump seeds, among the largest of any North American pine, “are arguably the most important fattening food available to grizzly bears during late summer and fall.” Loss of the whitebarks, the task force said, would endanger the bears’ survival. The hefty bears — a male can exceed 700 pounds — do not climb the trees. They raid messy, cone-stuffed middens on the ground that red squirrels build as winter storehouses. Grizzlies in northernmost Montana, Canada and Alaska have a wide variety of berries available in the fall, and those near the coast have spawning salmon in the rivers. But when winter looms in Yellowstone, “the whitebark pines are about it” on the bear menu, Dr. Mattson says.

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http://www.nytimes.com/2007/01/30/science/30bear.html?_r=1&oref=slogin