Wired Science

Climate Change-Driven Extinction

Climate change may spice up a few gardens; who doesn't want an exotic flower blooming within reach?—but it's likely to take its toll on a few, too. Some changes might even devastate entire ecosystems. Take the whitebark pine, native to the American West and Western Canada*. A pretty tree with snow-white bark and purple cones, the whitebark grows at high altitudes and in harsh areas, where it provides shelter to plants and insects that wouldn't be able to survive without it. It also provides an endless supply of protein-rich seeds to a number of wild animals.

But the whitebark pine is rapidly becoming a casualty of climate change.

"Time is running out here for the whitebark," says Diana F. Tomback, a biologist at the University of Colorado at Denver. According to the International Union for the Conservation of Nature and Natural Resources Red List of Threatened Species, the tree has already suffered population declines of up to 90 percent over recent years. And as the climate continues to change in the West, it's likely, scientists say, that the situation will only get worse.

For one thing, rising temperatures are driving the trees up into higher altitudes, where temperatures are cooler. Eventually, they'll get to the mountaintops and have nowhere left to go, says Diana Six, a forest entomologist at the University of Montana. But that assumes these trees are going to survive long enough to get there, she adds.

Six is alluding to two nasty infestations currently threatening the trees: blister rust fungus, an invasive species from Asia that attacks the trees’ branches and cones, killing them and preventing the trees from regenerating; and the mountain pine beetle, whose reproduction rates have recently doubled due to temperature increases.

The beetles are "developing much faster, they're reproducing more often, and a lot more are surviving," she says, which means that more trees—millions of them—are dying.

So what will happen to the big backyard of the American West if the whitebark pine disappears?

The trees are considered keystone and foundation species, which means their presence supports the survival of other species and they lend structure and stability to their ecosystem. So "if we lose them, there's a cascade of effects," Tomback says.

One animal that will be highly affected will be the grizzly bear--recently removed from the Endangered Species list-- which relies on the tree's seeds for food. "It allows them to fatten up for winter," says Six. Female bears, which become pregnant before they hibernate, depend on the seeds to nourish their growing young. "There's a real link between bear mortality and whitebark pine seeds," especially in Yellowstone National Park, Six says. In other words, the trees' extinction could spell a similar fate for the bears.

The trees’ seeds also feed black bears; birds, including finches, ravens, chickadees, and woodpeckers; and red squirrels and chipmunks, Tomback says.* Some birds, like the Clark's nutcracker, are crucial for dispersing and planting the tree's seeds, so the birds’ dwindling numbers are further exacerbating the trees' demise.

The whitebarks play an important role in providing water to the forest and valleys, too, according to Tomback. They shelter high-altitude snow, which slows the melting process, providing stream flow throughout the summer. In addition, the trees stabilize the soil so that the runoff is not as muddy as it otherwise would be. They are essentially providing a clean source of water that is important not only for scores of animals and plants, but also for ranching and agriculture below, Tomback says.

Although the Forest Service is working to protect the trees—by breeding populations resistant to the fungus, and then protecting these from beetles through the use of insecticides and other chemicals, says Gregg DeNitto, a group leader at the U.S. Forest Service—these efforts are still in very early stages, and many of the trees will be next to impossible to reach anyway. It doesn't help, says Tomback, that funding for the Forest Service has been cut in recent years.

Unless things change, the fate of the whitebark pine isn't looking good. And while no one can be certain exactly how its disappearance might transform the Western US, it's certain to leave a big mark—or a gaping hole.

"Ultimately, we don't know what the loss of this kind of thing means to the entire ecosystem.  It's kind of like a house of cards," says Patty Glick, a global warming specialist at the nonprofit National Wildlife Federation. But, Glick adds, "you're going to see changes in populations everywhere."

Photo by D.F. Tomback

Correction, Oct. 29, 2007: "British Columbia" has been changed to "Western Canada".

Correction, Oct. 29, 2007: The article originally and incorrectly stated that without the trees, these animals could seriously suffer. This implies that the species are suffering as a whole as a result of the Whitebark's decline. This is incorrect because the animals are present in other regions and ecosystems as well.