Threats posed by an imported disease and a tiny beetle to vital stands of whitebark pine trees near the roof of the Greater Yellowstone Ecosystem are to be addressed by a multi-tiered approach developed by the Greater Yellowstone Coordinating Committee.
Whitebark pines are a member of the "stone" pine family. They grow in the very highest reaches of Yellowstone, Grand Teton, Glacier, Rocky Mountain, Crater Lake, Yosemite, Sequoia and Kings Canyon national parks. These high-elevation trees produce a calorie-rich nut that grizzly bears in the greater Yellowstone ecosystem like to feast on in the fall. It's a nut that also feeds red squirrels and the Clark's nutcracker.
The sheer stature of the tree also helps maintain watersheds. In winter its bulk serves as natural snow fences, and in spring that same bulk helps shield the resulting snowbanks from the sun, thus allowing for a relatively slow and even snow melt.
Scientists regard the tree as a “foundation species” because it creates the conditions necessary for other plants and animals to get established in harsh alpine ecosystems. But the tree is in danger these days from non-native diseases, such as blister rust, and insects such as the mountain pine beetle, which are beginning to flourish in the trees' habitat thanks to climate change.
Last July the U.S. Fish and Wildlife Service officials announced that the agency would take a more extensive look at whether whitebark pine trees need protection under the Endangered Species Act. In a notice published in the Federal Register at the time, the agency acknowledged that substantial scientific and commercial information indicates that such a listing is merited.
Against that background, the Greater Yellowstone Coordinating Committee earlier this week released a "strategy" (attached below) for how to conserve whitebark pine in the face of both blister rust and pine beetles. The plan, five years in the making, calls for a variety of measures to be implemented, from inventorying whitebark stands to assess their condition from these two threats to identifying trees resistant to blister rust and which can be used as a seed source for growing resistant stands of whitebark.
Blister rust is an invasive disease thought to have arrived in North America in 1910 in British Columbia from France with imported eastern white pine seedlings. More than a few trees along Togowotee Pass between Dubois and Jackson to the east of Grand Teton National Park and just south of Yellowstone National Park already are infected with this disease.
While there are efforts under way to establish a strain of whitebark pine trees resistant to blister rust, there's no good solution to halting the mountain pine beetle, short of very, very cold winters. While a synthetic pheremone has been developed to ward off the beetles, its success has been limited.
"Blister rust can take years to kill a tree," according to Dr. Diana Six, a forest entomologist at the University of Montana who specializes in bark beetles. "When you have a beetle mass attack, it can take three or four days. It's just amazing because it doesn't take much to kill these trees."
Data obtained by the Greater Yellowstone Coordinating Committee shows that more than 50 percent of whitebark pine stands in the ecosystem "have already suffered high to complete mortality of overstory trees (from pine beetles) and 95 percent of forest stands containing whitebark pine have measurable mountain pine beetle activity. Blister rust is wide-spread and continuing to increase in incidence and severity. Infection rates in monitored GYA plots average 20%..."
Kelly McCloskey is an ecologist at Grand Teton who chaired the Whitebark Pine Committee for the Greater Yellowstone Coordinating Committee. She said Tuesday that monitoring of whitebark stands in both Yellowstone and Grand Teton already is under way, as is some seed collection from trees to gauge whether they are naturally resistant to blister rust.
“It's referred to as in-situ gene conservation," she said. "We’re trying to preserve the genetics of the trees out on the landscape.”
Collected seeds are sent to a U.S. Forest Service facility at Coeur d'Alene, Idaho, for propagation. Once the seedlings reach two years, they are sprinkled with blister rust spores to see if they support the disease, said Ms. McCloskey. Initial results could be available this summer from the first batch of collected seeds. Seedlings that prove resistant could be used to start a whitebark pine "orchard" in the Gallatin National Forest that could be used to reforest areas with the tree, she said.
While those tests are being conducted, the trees from which the seeds were gathered are protected from pine beetles by pheromone patches that drive off the beetles, said Ms. McCloskey.
The committee's strategy also calls for some hands-on work to slow the spread of blister rust, such as pruning to remove blister rust infections.
Within Yellowstone's 2.2 million areas there are an estimated 314,000 acres of whitebark pine stands; within Grand Teton's 333,327 acres there are an estimated 28,500 acres, according to the strategy document. Overall, the Greater Yellowstone Ecoystem, which includes the two parks and six surrounding national forests, covers roughly 14 million acres, according to the coordinating committee. Of that landscape, there are 2.5 million acres of whitebark pine.
Unlike lodgepole pine trees, which have evolved with pine beetles and developed defenses to slow the beetles -- thick, gooey resin that smothers the bugs, and even an odor that drives them away -- whitebark pines did not co-evolve with the beetles and have no similar defenses. They also can take 75 years of growth before they sprout their first pine cone. Plus, they rely largely on the Clark's nutcracker, which feasts on whitebark seeds, to, basically, plant new whitebark pine stands by caching seeds that later go on to germinate.
Barring a dramatic change from the current course of events, scientists fear the beetles will wipe out the mature whitebark pines. And the ripples of that episode will be felt throughout the ecosystem, where whitebark pine nuts are a key component of the grizzly bear's fall diet. As the days grow shorter and the temperatures fall, grizzlies spend most of their waking hours trying to pack on the pounds. Whitebark pine nuts are particularly nutritious, and in the Greater Yellowstone Ecosystem grizzlies seek out squirrel middens piled high with the pine cones to feast on.
Studies in the ecosystem have shown that when there's a good whitebark pine nut crop, sows gorge on them and head into hibernation both fatter and healthier. A key result is that they have larger, and healthier, cub litters than sows who go into hibernation with depleted reserves, according to Louisa Willcox, who heads the Natural Resource Defense Council's Wild Bears Project.