The highest-elevation tree throughout much of the Mountain West is the whitebark pine, often a last refuge for sun-weary hikers and other alpine inhabitants, including grizzly bears. But the tree's future is in jeopardy from disease and pine beetles. Photo courtesy of the U.S. Geological Survey.
For millennia, whitebark pine trees have held firm to the cold, rocky timberlines of the northern Rockies, Cascades and Sierra Nevada, providing shelter, food and other ecosystem services for mountain wildlife.
But before long, the hardy, snow-battered tree whose nutritionally dense seeds are a delicacy for grizzly bears, red squirrels and mountain birds may become functionally extinct.
In numerous reaches of Idaho, Montana, Wyoming and southern Canada, whitebark pine trees have declined by as much as 90 percent, experts say, and their prospects for recovery seem to be growing dimmer by the year.
"It's going and it's going fast," said Bob Keane, a research ecologist with the Forest Service's Missoula Fire Sciences Laboratory in Montana. "It's working itself from the north to the south to Yellowstone."
The culprits are a deadly pair of natural enemies: blister rust, an invasive fungus that infects whitebark pine and other "five-needle" pine species of North America; and the mountain pine beetle, whose spread to high-elevation forests has been aided by a warming climate.