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University of Colorado Denver | Anschutz Medical Campus

University of Colorado Denver, Newsroom

Diana Tomback, Ecologist

In her own words

My area of expertise is forest ecology, and my area of special interest is whitebark pine, a very important tree that occurs commonly at the highest elevations that our forests grow.
The whitebark pine is tough. It’s a survivor. But this tree is like a canary in the coal mine. It’s being impacted big-time by human-caused factors which are taking out this pine in huge numbers. For this reason, the U.S. Fish and Wildlife Service has evaluated the whitebark pine as a tree that warrants listing as threatened or endangered. It would be the first major forest tree to be on this list.
Whitebark Pine Clark's Nutcracker Diana Tomback Whitebark Pine blister rust Student at treeline Tomback with students

A Tree’s Everyday Business

In the subalpine areas where the whitebark pine lives, it plays an important role in everyday business. It produces large cones with nutritious seeds. Grizzly bears come around in the fall and steal these cones from the red squirrels to eat the seeds. We know that female grizzlies in the Yellowstone area that eat a lot of seeds have more surviving cubs, adding to the grizzly population. These trees provide protection for all kinds of wildlife, including elk, deer and birds of prey. Also, whitebark pine growing at high elevations shade the snowpack, so that the snow melts gradually, ensuring that by the end of the summer season there is still water flowing downstream. This benefits ranches and farms, as well as towns and cities.
As a doctoral student, I discovered that this hardy, important tree relies on one bird, the Clark’s nutcracker, for its future.This bird carries the seeds in its throat pouch and buries them, thereby determining where future whitebark pines will grow. Where the nutcrackers bury these seeds, the ecological world of the whitebark pine will follow— the bears, the birds, the elk, the shade for snowpack.

The Primary Threats

The whitebark’s ecological world is threatened by multiple factors:
  • Non-native disease called whitepine blister rust.
Americans inadvertently imported whitepine blister rust—a fungus that infects whitebark and its North American relatives—when we brought Eastern white pine seedlings into our country from Europe. We didn’t realize that with the seedlings came this invasive, destructive disease.The disease occurs nearly everywhere that whitebark pine occurs and is a major threat to whitebark pine survival.
  • Fire exclusion: a policy of excluding all types of fire from a specific wildland area.
Forests need fire for renewal. In some forest communities, whitebark comes in right after fire or other disturbance but, as time passes, is overgrown by shade-loving conifers, such as fir and spruce. Natural fire at at high elevations clears out the competitors and provides whitebark the chance to dominate again. A long-time policy of fighting fires has reduced the occurrence of fire in some high-elevation forests and resulted in the loss of whitebark pine. Shade-tolerant trees are now competing with the whitebark pine and crowding them out of existence.
  • Mountain pine beetle and climate change.
Warmer temperatures and drought have weakened whitebark pines, leaving the trees susceptible to mountain pine beetle infestations. At the same time, warmer temperatures let more beetles survive the winter. The two factors combined have been devastating to populations of this tree. 

At Stake: Biodiversity and our Natural Heritage

It’s true that there’s nothing left that’s pristine, but losing the whitebark pine is a big bite out of our forest primeval throughout the West.
Losing this tree means we lose food and shelter for wildlife—birds, small mammals and large mammals. When we lose this tree, we have less food for grizzly bears, and that means the bears wander looking for food and get into trouble with people. Bears in trouble with people inevitably lead to dead bears.
We are also losing a vast amount array of unique forest biodiversity, part of our natural heritage—no longer there for future generations. We lose nature’s services to us as well, and instead we get faster snowmelt and less water later in summer, less shelter and food for wildlife and game at high elevations, and a longer wait for forest renewal after fire.

Saving an Ecosystem

People often ask—so what are you doing about this?
In 2001, with a small group of federal and university researchers and resource managers, we founded the non-profit Whitebark Pine Ecosystem Foundation {}, which is dedicated to the restoration of whitebark pine ecosystems. I have served as volunteer director of this foundation since its inception, andthrough this organization, we are educating people across the country as well as NGOs and government agencies about the loss of biodiversity we face if we lose this tree.
Ultimately, what I am doing is continuing my research to learn more about the ecological roles of whitebark pine. Since 2007, my students and I have studied treeline ecosytems in Glacier National Park, on the Blackfeet Tribal Lands in Montana, and also on the Beartooth Plateau north of Yellowstone. There we continue to study and carefully watch—and worry about—this foundation and keystone species for high-elevation ecosystems.
Published:  September 4, 2012