Whitebark Pine: A Subalpine Keystone Struggles to Survive

by Megan Kirkpatrick

High up in the mountains, a tree called whitebark pine (Pinus albicaulis) shows us just how interconnected our natural world is. This tree is vital to our subalpine ecosystems and much of the life that exists below them. It plays a critical role in protecting water resources, providing food and shelter for numerous species of plants and wildlife and in shaping the aesthetic of our high-elevation recreation destinations. Whitebark pine is a keystone species, meaning it is so critical to the ecosystem that its loss would radically change the landscape.

The whitebark pines provide shelter and food for many other species, as well as helping regulate water suplies. Photo by Diana Tomback.

Yet whitebark pine is in trouble, having suffered significant mortality in recent
decades from multiple sources. An introduced fungal pathogen called white pine blister rust has infected stands all across its range. In addition, warming trends have allowed the mountain pine beetle to climb higher than ever before, reaching subalpine terrain where the trees are already weakened by blister rust. Past fire-suppression practices also threaten this species. Lowlevel fires historically helped remove fire-intolerant trees such as subalpine fir and Engelmann spruce, but those species are now out competing whitebark pine.

Whitebark pine has an important friend, a bird called the Clark’s nutcracker (Nucifraga columbiana). The tree and the bird are obligate mutualists, meaning they are reliant on one another for survival. Whitebark pine is dependent on the nutcracker as its main mechanism for seed dispersal. The cones of whitebark pine do not open on their own. Within these cones are fatty seeds, packed with calories that the bird craves. They use their strong beaks to pry them loose, carrying tens of thousands of them each year to cache spots, a sort of subalpine pantry. Because the seeds are large and do not have wings to be carried on the wind, this habit allows for seed dispersal. The nutracker plays an important role in the future of whitebark pine regeneration, as the seeds that are not retrieved have the potential to germinate. Together, the bird and the tree have a relationship that benefits countless plant and animal species. The seeds also serve as an important food source for grizzlies and black bears as well as songbirds and squirrels, and the tree itself provides shelter and nesting sites for many species.

The significance of this relationship to mountain ecology is multiplied by the value the trees provide for people. Whitebark pine plays an important role in hydrology. Being the highest elevation trees, they help regulate runoff by shading and retaining high mountain snowpack. This prevents flooding as well as summer droughts, an important factor in protecting water supply and wildfire prevention. The loss of this tree could impact ecological functioning, biodiversity, species distribution and the aesthetic beauty of many of our national parks and wilderness areas.

So the next time you are backpacking and come across a whitebark pine, or hear the “kraaaak” call of the nutcracker, take a moment to appreciate the delicate bonds that surround you and the powerful ways they shape our world.

The Clark's nutcrackers and whitebark pine rely on eachother for survival. Photo by Mordechai Treiger.

Where to see whitebark pine

Whitebark pine grows in the highest-elevation forests (typically 5,000 feet and above in Washington) and at the timberline. In Washington, it is found all along the Cascade Crest in most of our wilderness areas and national parks. High elevations of the Pasayten and eastern Cascade portions of the Glacier Peak Wildernesses are excellent locations to view this tree. It can be identified by its upswept needles that grow in clusters of five and are 1.5- to 3-inches long. The bark is smooth and pale gray, and its cones are rounded and purple, about 2.5-inches long and bearing pointed scales. In the harshest environments, wind twists and contorts the trees, which can also grow in a dense shrublike form known as krummholz.

What is being done for whitebark pine and how you can help

Currently, several groups are researching ways to protect and restore whitebark pine. To learn more about the issue and other ways that you may help, go to whitebarkfound.org.