In the Rockies, Pines Die and Bears Feel It

This article about the relationship between mountain pine beetles and grizzly bears struck a chord with me. I've been worried for some time that global warming might lead to the extinction of certain tree species within my lifetime, as niche environments change and weakened trees succumb to various threats. This article makes the case that extinction of the whitebark pine, Pinus albicaulis, is a real possibility in the not-so-distant future:

Dr. Logan enters the fray on the question of what grizzly bears eat, how much of it will be available in the future, and where. All that, he says, hinges on the mountain pine beetle and the whitebark pine.

The tree (Pinus albicaulis) has no value as commercial timber. But gnarled and bushy whitebark pines anchor the timberline in much of the West. They hold the soil for other vegetation to get a foothold, and they trap snow, prolonging the spring runoff.

They are slow-growing trees and may not even bear cones until they are a half-century old. In the late 19th century, the naturalist John Muir counted rings in a weatherbeaten example high in California’s Sierra Nevada. Its trunk was just six inches across. To his astonishment it was 426 years old.

The beetle’s usual targets were once midaltitude lodgepole and ponderosa pines. But it has begun extending its range as it adapts to warming temperatures in the Rockies — two degrees since the mid-1970s. As a result, it has been killing whitebark pines at altitudes in the Rockies and the Cascades of Oregon and Washington that would have once been too cold.

Beetle attacks have added to the toll taken by a disease called white pine blister rust. In the northern Rockies, the beetle infests 143,000 acres. Entire forest vistas, like that at Avalanche Ridge near Yellowstone National Park’s east gate, are expanses of dead, gray whitebarks.

“We are very worried the whitebarks may be locally extirpated, if not driven extinct,” said Diana Tomback, professor of biology at the University of Colorado, Denver, and president of the Whitebark Pine Ecosystem Foundation, a nonprofit organization. One recent Forest Service study suggested that in the next century a global warming would reduce by 90 percent the acreage that has the kind of cold and high altitude climate where the trees now grow.

If you love trees, then this article is worth a very close read. Some of the quotes from folks who have spent their careers studying the biology of this ecosystem--and who are now watching it disappear, year by year--are heartbreaking, both for the destruction described and for the obvious distress of those quoted.

Link: In the Rockies, Pines Die and Bears Feel It - New York Times.