"This is not your ordinary pine tree," said Diana Tomback, a professor of biology at the University of Colorado-Denver, one of the nation's leading experts on whitebark pine. She stood before a whitebark pine tree in the high country of the greater Yellowstone ecosystem.

Biologists including Tomback have known for only a few decades that the high fat content of whitebark pine nuts helps grizzly bears fatten up for winter's hibernation. The bears raid squirrel middens or caches of stored whitebark pine nuts in the fall, adding on the layers of fat that will get the bears through long winters, and improve the odds that grizzly mothers will have successful pregnancies.

Grizzlies are attracted up into the high country, away from people, where the whitebark pine dominates the timberline with its spreading canopies and wind-battered trunks and limbs. Yet when whitebark pine nut crops fail or do poorly, grizzlies tend to abandon the high country in search of food. That means trouble for bears and people alike.

Good years for whitebark pine seed production mean good years for grizzly bears - abundant food far, far away from livestock, birdfeeders, orchards, garbage and other temptations in valley bottoms crowded with roads, development and people.

Trouble is, Tomback said, whitebark pines aren't having many good years these days.

Problems

The first problem facing whitebark pines is an altered fire regime in the last century or so, Tomback said. In pre-settlement times, American Indians made frequent use of fire as a tool to improve forage for game, and later horses. These frequent fires, over several centuries, created diverse patterns of forest species, varied ages of tree species and tree species replacing one another in succession.

In and around timberline, the whitebark pine would be replaced by shade-tolerant conifers - if fires didn't periodically remove the conifers and give the whitebark pines an opening.

Fire suppression in the post-settlement era has meant fewer fires and thus fewer opportunities for regeneration of whitebark pines. That means fewer young whitebark pines and a majority of older, mature whitebark pines.

That sets the stage for problem No. 2: white pine blister rust, an exotic species native to Eurasia and inadvertently introduced to western North America in 1910 near Vancouver, British Columbia. The blister rust attacks the family of five-needled white pines, Tomback said, entering through the needle stomata, growing into branches and stems, then erupting as spore-producing cankers that kill the branches and end cone production. Blister rust can take up to a decade before it kills a tree - a slow-moving but relentless cataclysm.

As the fungal disease spreads south and east, it leaves behind "ghost" forests, Tomback said - stands of dead whitebark pine and mortality rates of 90 percent or higher. Blister rust has already spread to southern California, east through Idaho and Montana, south to Colorado and Nevada. It is already present in the greater Yellowstone ecosystem, Tomback said. A recent inventory says 25 percent of whitebark pines in the Yellowstone ecosystem have rust.

"It takes out cone production first," years before the tree dies, Tomback said. That means no seeds for birds, squirrels and bears.

Unlike their salmon-eating kin in Canada, or berry-eating cousins in Glacier National Park, Yellowstone grizzlies really don't have a high-calorie substitute for the loss of whitebark pines to blister rust.

The hope for whitebark pines in the face of the blister rust epidemic is that some trees are resistant and pass that resistance on to seedlings, which can be replanted in the wild, until genetic resistance to blister rust is well-distributed. That will take a lot of money and between 50 and 150 years to show results. It takes 50 years for whitebark pines to start producing seeds and 150 years until seed production peaks.

New firestorm

If blister rust can be regarded as a steadily, if slow-moving, disaster for whitebark pine, the relatively dramatic and sudden attack of mountain pine beetles can be regarded as a biological firestorm, fueled by global warming, experts at a recent workshop sponsored by the Natural Resources Defense Council said.

In the past, when the high-altitude environment of the whitebark pine also meant bitterly cold temperatures, mountain pine beetles couldn't mount effective attacks. "Whitebark pine stands were effectively a mortality sink for pine beetles," said Diana Six, a University of Montana entomologist.

"With cold temperatures and a short growing season, when beetles actually did make it up there, they took more than one year to develop - in fact, often two years," she said.

A two-year life cycle means the beetle would need to go through two winters and survive in a tree that is dead for two years. That means the tree would be dry and much reduced as a food source. Also, Six said, past winters were very cold, and high mortality occurred to the beetles over the winter - often upwards of 80 to 90 percent - leaving few surviving insects to emerge and attack new trees the following year.

"The beetles need to mass attack trees to kill them, and if numbers are very low when they emerge, they aren't very successful," she said. "So, essentially, in the past, the beetles sometimes moved upslope from infestations in lodgepole pine, killed some trees and then pooped out."

A few years ago, Six was stunned to find sites where the mountain pine beetle was skipping right over lower-altitude stands of lodgepole pines, to focus on and kill whitebark pine stands at higher altitudes.

Colleague Jesse Logan, now a retired Forest Service entomologist, noticed the same thing. His whitebark pine research plots in the White Cloud Mountains of Idaho were first attacked by mountain pine beetles in 2001. In two years, the whitebark pines were all dead.

"It is amazing how fast this is happening," Logan said.

He is seeing the same, rapid onslaught of mountain pine beetles in the whitebark pine stands of Wyoming's Togwotee Pass, and Avalanche Peak in Yellowstone National Park.

Warming to blame?

Since then, Six and Logan learned that with warmer winters and longer growing seasons, the pine beetles are going through a entire life cycle in one year, experiencing little winter mortality, and emerging the following spring in large numbers. That all translates to more regular, massive outbreaks in a system where such outbreaks have been exceedingly rare and weak in the past.

And because pine beetle outbreaks have been rare in the past, whitebark pines have not evolved effective defenses. Indeed, some research suggests that whitebark pines have half of the sap moisture that lodgepole pines can produce, meaning whitebark pine can't "pitch out" the invaders as lodgepole can.

"A weak defense system means that it takes fewer beetles to kill a tree than it would, in say, lodgepole pine, and that an epidemic can develop much faster," Six said. "A weaker defense system may also be why we are seeing a strong preference now by the beetle for whitebark pine over lodgepole pine, which has long been its preferred host."

Six said that blister rust, drought and the ongoing pine beetle outbreak are each bad for whitebark pines, in and of themselves. "Two or more at the same time are overwhelming," she said.