Last chance for the whitebark pine
A remarkable tree, spread by birds andeaten by bears, finally gets someattention
MISSOULA, Mont. - High atop Beaver Ridge on the Montana-Idaho border, a neglected tree species is making its last stand.
Moss-adorned 60-foot-tall snags that were once thriving whitebark pine trees stand like ghosts in this forest now dominated by subalpine fir.
Years ago, the pine with the cones that point skyward provided tons of big nutritious seeds that at least 110 different animal species, ranging from small birds and mice to grizzly bears, loved to eat. Now, the few solitary, centuries-old trees that still cling to life here and in the neighboring Bitterroot-Selway Wilderness are facing local extinction.
In Glacier National Park, the species is down to 5 percent of its historic range. In areas around Missoula, 60 percent to 80 percent of the trees have died. In the Bob Marshall Wilderness, trees are also dying at a fast clip.
A tree is overlooked
For decades, the stark gray snags crowding the ridgelines like moss-covered gravestones failed to ring an alarm.
Ecologists first thought the massive die-offs were part of the tree's natural cycle. Timber scientists weren't very interested in the slow-maturing, low-value tree that grows at high elevations.
The die-offs began in the 1930s, when mountain pine beetles swarmed through the forests, a natural cyclical phenomena. The tiny beetles dig egg chambers in the cambium of a tree. Under regular circumstances, whitebark pine would resist the beetles by clogging the egg chambers and entry holes with pitch. But the tree came under stress at the same time from an exotic disease from France called white pine blister rust.
Fire ecologist Steve Arno first noted the massive decline in the 1960s. Arno eventually recruited Bob Keane, an ecologist with the Forest Service's Fire Sciences Laboratory in Missoula, Mont., to unravel the tree's ecological secrets.
For four summers, Keane camped in the Bob Marshall Wilderness, observing an astounding relationship between the whitebark pine and its wildlife neighbors.
Biologists had already recognized the tree as an important wildlife food source - particularly for bears. Red squirrels cache the seeds, then bears pilfer those caches. Bears crave the oily seeds so much that, if offered the option, they will choose them over salmon.
In Yellowstone National Park, whitebark pine seeds account for up to 48 percent of a grizzly bear's annual diet during a productive cone crop year. When the late summer seed crop is abundant, bears are rarely seen at low elevations. When the crop fails, there is always a dramatic increase in human-bear encounters in the valleys.
Keane monitored an even more curious animal-tree relationship that was first brought to light by biologist Diana Tomback of the University of Colorado at Denver.
Whitebark pine cones develop facing skyward and hold onto their seeds so that they never fall to the ground. There has never been a documented case of a seed germinating beneath a parent tree. Even if they could get free, the seeds do not have wings that would allow them to float to open areas. Instead, a feathered friend - the Clark's nutcracker - disperses the seeds.
Come late summer, Clark's nutcracker will break open a cone, extract a mouthful of seeds and fly to an open area to bury them. Each bird picks up to 110,000 seeds every summer, hiding them in about 8,000 different spots.
"The bird is a caching machine," Keane says.
Either the bird can't remember all the locations of the caches, or it isn't hungry enough to eat all the seeds, because each bird ends up ingesting only about 85,000 seeds a year, giving the rest a chance to germinate.
But the nutcracker doesn't hide its caches in any old clearing, Keane discovered. The seeds develop into trees only in disturbed soil, as in a recently burned area free from competition from other plants - which is the main reason why whitebark pine has not been able to rebound after its crises with disease and insects.
"Modern fire-suppression tactics over the last 80 years have stopped fires from reaching the high mountain tops where the tree lives," Keane says.
Fire would not only prepare suitable caching areas, it would also keep the shade-tolerant subalpine fir in check.
"When subalpine fir even see a fire, they just throw up their hands and lie down," Keane says. From his research in the Bob Marshall Wilderness, Keane estimates that subalpine fir now dominates 22 percent of the traditional whitebark pine habitat. Historically, the fir only grew in about 8 percent.
"Without fire, fir will overtake an area in three to four decades," he says.
A complex prescription
On Beaver Ridge, saw crews were busy last summer thinning firs from some areas to stimulate growth and cone production in whitebark pine, as well as clear-cutting 1- to 2-acre plots to create nutcracker caching sites. After setting prescribed burns, workers will replant some areas, and leave others to the nutcracker.
But thinning and reseeding will prove fruitless in the future unless wildfire is allowed to return to the ecosystem, says Keane:
"The only way to perpetuate the species is to open up areas for caching. That means fire, because innovative methods like thinning and clear-cutting won't always work. First of all about 49 percent of the whitebark range is located in wilderness areas where you can't even use a chainsaw."
But there are major problems with prescribed, or controlled, burning. The time frame for prescribed burns at high altitudes is short because of heavy snows. Many sites can't even be reached by vehicle until mid-June. On Beaver Ridge, snow often tops the 22-foot-high weather tower long after spring arrives in the valleys.
"Usually, when the whitebark pine area comes into prescription, the lower forests are at a tinderbox dry condition," Keane says. "The best treatment is to let wildfires in wilderness go at high elevations and drift upslope and burn themselves out at the tree line. And only control them if they come near people or property."
Keane will never live to see whether his efforts to save the whitebark pine are successful. It often takes 10 years before a burn site becomes conducive to whitebark seedling survival. Grasses and forbs must first create enough ground cover to hold soil moisture. Then it takes another 20 to 40 years before seedlings become functional trees. And then another 20 years before they start producing cones.
But once they get established, trees that escape the rust, beetles and crown fires can "live for a very long time," Keane says, often for centuries.
Mark Matthews writes from Missoula, Montana.
This story was made possible by contributors to the High Country News Research Fund.
You can contact ...
- Bob Keane at the U.S. Forest Service Rocky Mountain Research Station, Fire Sciences Laboratory, 406/329-4846.
Copyright 2000 HCN and Mark Matthews