This is an ecological ballet, as most ecosystem descriptions are. Instead of a young girl, a weird uncle, a decorative kitchen utensil with a sword, and armies of mice, its corps de ballet includes birds, trees, squirrels, grizzly bears, alien invaders (lots of aliens), and even Indians and their successors. It is set on a stage above 8000 feet extending from Yellowstone to Glacier National Park.
The final acts remain unfinished, subject to revision. It is rated R, since it contains some sex and violence. You may wish to provide your own adult language.
The whitebark pine is a member of the family of 5-needled pines, which also includes the white pine, western white pine, and limber pine. The whitebark pine lives at high altitudes, primarily in the US and Canadian Rocky Mountains, especially in Glacier and Yellowstone National Parks and the surrounding National Forest and wilderness areas. It's most often found at altitudes above 8000 feet. It's a slow growing pine and lives about 300 years. After 50-75 years it begins producing cones, but the cones never open or drop to the ground to spread the seed.
Whitebark pine seeds are planted by a bird - Clark's Nutcracker (this really is about nutcrackers). The nutcracker doesn't remove the cones from the pine. Instead, the nutcracker's long beak removes the seeds, which the bird stores in a specialized pouch under its tongue - up to 150 seeds at a time.
Surplus pine seed is stored, usually in the ground for later consumption, in numerous caches of 5-10 seeds each spread over a wide area--up to 20 × 20 kilometers (12.5 × 12.5 mi) [That's over 150 square miles]. The birds regularly store more than their actual needs (up to 33,000 seeds per bird!) as an insurance against seed theft by other animals (squirrels, etc.); this surplus seed is able to germinate and grow into new trees, thus the bird is perpetuating its own habitat. Closely tied in with this storage behaviour is the bird's remarkable long-term spatial memory; they are able to relocate caches of seeds with remarkable accuracy, even six months later, and even when the cache sites are buried under up to a meter (3 feet) of snow.
Clark's nutcracker.
Sometimes red or pine squireels raid the nutcracker's seed caches, but more often they cut the pine cones from the branches using their teeth. Squirrels bury pine nuts and pine cones in shallow caches called middens.
By autumn, grizzly bears enter a stage called hyperphagia. The bear needs enough calories to not only maintain its 400-1500 pound body weight, but must accumulate enough fat - up to 30 pounds each week - to last through 4 to 7 months of hibernation. A female may gestate and produce milk over that period as well. Bears wouldn't hibernate at all if food resources were sufficiently abundant in their habitat year 'round, - but they aren't. Bears eat while they can, and sleep when they can't.
A pine nut (and nutcrackers, squirrels and bears all appreciate this fact despite the lack of nutritional labeling) is 21% protein, 21% carbs, and 52% fat by weight. The bear might make a precarious living by scouting over 150 square mile areas for nutcracker caches of a few seeds each, but the squirrel's middens are an all-you-can-eat feast fit for an animal - well - as hungry as a bear. A grizzly can locate middens under six feet of snow.
This is a tidy ecosytem with a mutual relationship between the nutcrackers and pines, and the bears dependent on the trees and squirrels. Squirrels are a necessary player because grizzlies are not good climbers - a useful fact to remember should you meet one, since they're omnivores. But since they're omnivores, how dependent are the bears on pine nuts?
During good cone crop years, Yellowstone bears feed almost exclusively on pine seeds in the autumn (Mattson and Reinhart 1994).
Furthermore, seeds from exceptionally heavy cone crops can dominant bear food consumption in the following spring and summer (Kendall 1983, Mattson et al. 1994). Grizzlies in the Yellowstone area obtain one-quarter to two-thirds of their net digested energy from pine seeds, depending on the size of the cone crop and relative abundance of alternative high-quality foods (Mattson at al. 1999).
Because whitebark pine seeds are such an important source of energy and dietary fat in the Yellowstone area, the availability and consumption rate of seeds influences grizzly bear demographics. Adult female grizzlies that eat more pine seeds have more surviving cubs than females who eat fewer pine seeds (Mattson 2000).
There also is a strong relationship between the whitebark pine cone crop size and grizzly bear survival. During years when pine seeds are scarce, conflicts with humans and the human-caused grizzly bear death rate escalate dramatically (Mattson et al. 1992, Mattson 1998, Pease and Mattson 1999). This is a function of the distributions of whitebark pine and humans.
Whitebark pine primarily occurs at high elevation while most towns and roads are located in valleys at lower elevations. When pine seed crops are large, bears are found in whitebark pine stands – far from most humans. When seed crops are small, bears tend to forage for alternative natural foods such as clover or yampa roots that occur at lower elevations closer to human facilities (Mattson et al. 1992).
Whitebark Pine Ecosystem Foundation
When sex and age-specific mortalities were examined, researchers determined that 2.3 times as many adult females and 3.3 times as many sub-adult males suffered human-caused mortalities during years when they did not use whitebark pine seeds, and that total human-caused mortalities increased 1.9 times during these years.
Whitebark Pine Seeds, Red Squirrels, and Grizzly Bears:
An Interconnected Relationship
But there is one other necessary factor that keeps this ecosystem functioning: fire.
Whitebark pine benefits from wildland fire because it is better adapted to surviving and regenerating after fire than its associated shade‑tolerant trees (Arno and Hoff 1990). Whitebark pine is able to survive low severity fires better than its competitors because it has somewhat thicker bark, thinner crowns and deeper roots.
The species also readily recolonizes large, stand‑replacement burns because its seeds are transported great distances by Clark’s nutcracker. Nutcrackers can disperse whitebark pine seeds up to 100 times farther (over 10 km) than wind can disperse seeds of subalpine fir and spruce (McCaughey and others 1985; Tomback and others 1990; Tomback and others 1993). Essentially all whitebark pine regeneration comes from unclaimed nutcracker caches, where seeds eventually germinate and grow into seedlings (Keane and others 1990).
Nutcrackers prefer open sites with many visual cues for seed caching, much like the burned stands after a mixed or stand-replacement fire (McCaughey and Weaver 1990; Sund and others 1991; Tomback 1989; Tomback and others 1990; Tomback 1998). Mixed severity and stand-replacement fire regimes are primarily found in the whitebark pine forests of the northern Rocky Mountains and Intermountain regions.
Whitebark Pine Ecosystem Foundation
For an explanation of where fire historically came from in North American ecosystems, you can see this diary: How to Build a Forest. The short answer is that while natural (lightning caused) fires occur infrequently, most fires were started by Indians for various useful purposes. After Euro-settlement, Indians were removed from the ecosystem and fire suppressed - heavily suppressed during the first two-thirds of the twentieth century.
Fire is the keystone disturbance that shaped most whitebark pine landscapes, so treatments should be designed to emulate fire’s historic effects on the landscape (Keane and Arno 2001). While prescribed fire is the obvious tool, mechanical cutting treatments can also be effective. Properly designed silvicultural thinning can simulate the effect of non-lethal surface fire in whitebark stands (Keane and Arno 2001).
Whitebark Pine Ecosystem Foundation
In pre-[Euro]settlement times, Native Americans 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 and generations of forest species. In and around timberline, the whitebark pine would eventually 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-[Euro]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.
Important Food Source for Grizzly Bears In Trouble
The shade-tolerant conifers referred to are species like subalpine fir and Engelman spruce. They grow much faster than whitebark pine, and since whitebark pine is not shade-tolerant, will crowd out whitebark pine reproduction. If thinning is done, it's the pine's competitors that would be thinned or removed, just as fire would do. Still, whitebark pine have one other advantage - at above 8000 feet, the weather is terrible, very cold. Except:
GLOBAL WARMING
Climate change is likely to impact whitebark pine significantly over the next century. Long life span and late maturity of whitebark pine limit its ability to adjust rapidly to change. Three models showed that under current projections of a doubled CO2 level, whitebark pine will be reduced to less than 10% of its current range in Yellowstone National Park, where it is a major component of alpine and subalpine ecosystems (Mattson and Reinhart, 1994). The warmer climate will favor less-hardy species which heretofore have been restricted to lower elevations by temperature, but will likely find more opportunities to compete with whitebark pine at higher, more rugged locations. Whitebark pine will be less successful at regeneration, and future stands are likely to be more mixed. Implications of this decline are severe, since bears in this area rely heavily on whitebark pine seeds for food year-round.
Management of Whitebark Pine
While the whitebark pine's survival chances are made worse by climate change, the re-introduction of low-intensity fire and/or mechanical thinning could possibly keep the problem under control. In fact the whitebark pine's (and grizzly's) most serious problems aren't caused by global warming - there's something much worse:
White pine blister rust, a fungal disease caused by the pathogen Cronartium ribicola, was inadvertently introduced to Vancouver, British Columbia in 1910. In the past century, it has spread nearly rangewide in P. albicaulis [whitebark pine], except for interior Great Basin ranges (Kendall and Keane, 2001, McDonald and Hoff, 2001, Tomback and Achuff, MS.). The highest infection levels in P. albicaulis , 50-100% , occur in the northwestern U. S. and southwestern Canada (Kendall and Keane, 2001). Whitebark pine mortality from the combination of blister rust and mountain pine beetle exceeds 50% in areas including Glacier National Park, northwestern Montana, north-central Idaho, and northern Washington (Kendall and Keane, 2001)
Whitebark Pine Ecosystem Foundation
Readers of Aldo Leopold's essays may recall his adomontion that if you're going to plant white pine (in Wisconsin - white pine is a whitebark pine cousin) you should remove currant and gooseberry bushes, which are an alternate host for blister rust (Leopold died in 1948 - blister rust was already a problem then). Efforts to eradicate currant and gooseberry over 40 years were largely a failure. There is no chemical or biological remedy or preventative for blister rust. Thinning the pines won't reduce blister rust's spread (as thinning will for mountain pine beetles in lodgepole pine, for example).
But again, there's some hope. Around 5% of whitebark pines are immune to blister rust, and programs are underway to propagate immune strains to replace dying stands.
Whitebark pine is not a commercially important species for timber and, therefore, has not received much attention in terms of resistance breeding. This is unfortunate, as Schmidt (1992) estimated that 80-90% of the whitebark pines in Montana's Glacier National Park and the Bob Marshall Wilderness area have blister rust.
White Pine Blister Rust - Cronartium ribicola
And here's where the final problem comes in. The Yellowstone-Glacier ecosystem includes National Forest, National Parks and wilderness areas (Selway-Bitterroot and Bob Marshall - over 1 million acres each). Remedying this problem requires intervention into these areas - re-introducing fire, thinning, re-planting, on-going maintenance. While it's arguable that existing law allows these activities, and proposed legislation expanding wilderness in the area includes provisions for restoration (somewhat vague, but including establishing a national restoration corps), the availability of funds sufficient to accomplish the task in time is questionable, and the legal status and enviro-political climate make challenges to this (and similar problems and interventions) likely. Major environmental groups, like the Sierra Club and Wilderness Society recognize the problem, but don't seem to be doing much to educate the public about it, and while they support some intervention, seem coy about the extent to which they would support things like wilderness restoration - or in some cases restoration outsideof wilderness as well.
The bottom line is that, while global warming exacerbates some environmental problems, it doesn't cause all of them. Fixing global warming won't be that helpful in maintaining grizzly populations in MT and WY. Leaving this ecosystem alone to "restore the natural balance" is also not going to do anything but reduce grizzly numbers. Eliminating the capitalist system won't keep grizzlies alive, nor will community gardens. In this case, we know what to do, although even then, success will be difficult to achieve. The solution is human intervention in ecosystems that have been seriously disturbed. Climate change only makes intervention more imperative.
This isn't a problem that can be blamed on logging or development, or even CO2. To be sure, it was human caused nearly 100 years ago by the introduction of pathogens and the exclusion of fire, This is one of a set of problems that demands attention and intervention - the same pattern repeats itself in western forests and wildlands, whether it's overly dense lower altitude forest, or mountain pine beetles attacking even-aged lodgepole pine stands from British Columbia to Colorado, or invasive species, like cheat grass or red brome, invading and dominating ecosystems. Even the west's water problems will exist whether the temperature goes up or down.
If ever there was an issue where solution demands people to be reality-based instead of spiritual, or science-based instead of ideological - this set of problems is it. What's a wilderness (or National Forest, or National Park) for, if not for bears?
Final note: (as if this isn't long enough) Grizzlies have other problems. Another favorite food is moths - low in calories individually, but bears can find and consume thousands each day. Moths in this ecosystem are threatened by pesticides. Grizzlies also prey on elk, deer, and other large mammals (including sheep and cows) - the reintroduction of wolves adds a layer of food competition for grizzlies. Wolves have been observed driving bears away from their own kill.