Sitting atop the highest slopes in western North America, the whitebark pine has adapted to the continent’s harshest growing conditions. Temperatures in the sub-alpine zone where it thrives are often well below zero, snow is measured in feet, and winds often exceed 100 miles an hour. These stout, twisted trees are survivors: The oldest have grown for nearly 13 centuries.
But change has come to this high-elevation redoubt, threatening not only the whitebark pine’s survival but that of a host of creatures — from birds to bears — that rely on this keystone species. Warmer temperatures, a fungal disease called white pine blister rust, and swarms of mountain pine beetles have killed hundreds of millions of whitebark pines across the West. Wildfires are taking an increasing toll, and other conifer species are moving upslope in the rapidly changing environment, outcompeting the whitebark for nutrients and moisture.
In some areas, including regions within the Northern Continental Divide Ecosystem, which has Glacier National Park at its center, more than 90 percent of whitebark pine trees have died. Across the tree’s range, there are more dead trees than live ones, and high-country skylines in many places are marked by their skeletal remains.
Last month researchers finished sequencing the genome of the whitebark pine, using DNA from a healthy tree.
But recently, efforts to conserve and restore the whitebark pine have ramped up. Scientists using new genetic techniques are racing to find disease-resistant trees to breed and plant in decimated areas. In December 2022, the U.S. Fish and Wildlife Service listed the whitebark pine as threatened — Canada considers the tree endangered — and the agency is currently developing a species recovery plan. Meanwhile, the Whitebark Pine Ecosystem Foundation and the conservation organization American Forests — in consultation with the U.S. Forest Service, the National Park Service, the Bureau of Land Management, and tribal governments — are creating a roadmap for restoration that focuses on prioritized areas.
The new initiatives build on other long-running efforts to restore the whitebark pine. For many years across the high-mountain West, researchers and managers have combed dead and dying whitebark pine stands to find trees that are still green and healthy. They gather their cones, then grow out the seeds to seedlings in a greenhouse for two years, subjecting them to spores of blister rust. (The Forest Service operates tree research facilities in Idaho and Oregon, and the Confederated Salish and Kootenai Tribes are building a second, large greenhouse on their reservation in western Montana.) The seedlings are then planted outdoors and monitored.
Those that survive another two to three years are replanted in areas where spores are likely present and monitored for at least another three to five years. The survivors of this round will be transplanted to federal and tribal lands around the country. These are the elite trees upon which the future of the whitebark pine forest rests.
Obviously, identifying disease- and climate-resistant trees is a long-term project: it takes 30 years for a tree to produce a cone, and as long as 80 years to produce nut crops large enough to play a functional role in the ecosystem. The effort is also expensive, costing between $1,200 and $1,800 per tree. The good news is that last month researchers at the University of California, Davis finished sequencing the genome of the whitebark pine, using DNA from a healthy tree near Bend, Oregon.
It was no small task — conifer genomes are three to 10 times larger than the human genome. But evolving genomic technologies have slashed the sequencing time. This breakthrough will enable researchers to develop a way to rapidly identify trees that are both resistant to white pine blister rust and adapted to warmer and drier conditions linked with climate change.
The sequencing of conifer genomes will allow for targeted restoration with trees that can resist drought and pathogens.
“We’re trying to create a 23andMe for trees,” said David Neale, the chair of the Whitebark Pine Ecosystem Foundation and head of the Whitebark Pine Genome Project, referring to the company that sequences human DNA to reveal health and ancestry information. “A forester goes out and collects a small number of needles from hundreds, thousands, tens of thousands of trees, sends them [to a lab], and gets back a report as to the risk or potential resistance to a pathogen. It will reduce the time it takes to identify the trees from years to weeks and cost only $100 per tree.”
Neale and his associates have also sequenced genomes of the giant sequoia, coastal redwood, and sugar pine, among other trees. Conifers are on the front lines of climate change in many places, and having the genomes sequenced will allow targeted restoration with genetically vital trees that can resist drought and pathogens. Nearly 20 percent of large sequoia trees have been lost as the climate has become hotter and drier and wildfires have become more frequent. Insects are also a growing threat to a large number of trees.
White pine blister rust is an invasive fungal disease native to Asia. It traveled to the U.S. in a load of white pine seedlings imported from Europe in the early part of the 20th century. It spread from the West Coast on the wind, traveling into whitebark pine country in Idaho, Montana, and other mountain regions. It wasn’t until the 1990s, though, that people became concerned about its impact on whitebark.
To varying degrees, the rust has affected all of the five-needle pines in the West — which in addition to the whitebark pine include limber, Western white, foxtail, and sugar pine. It has not yet been seen in the Great Basin bristlecone pine, the longest-lived tree in the world. (The famed Methuselah tree, in the Inyo National Forest, is a member of this species.)
“People are vigilant” when it comes to the bristlecone, said Diana Tomback, a professor of integrative biology at the University of Colorado, Denver, and the policy and outreach coordinator for the Whitebark Pine Ecosystem Foundation. “Experiments show it’s susceptible to blister rust. But it grows in very cold, dry environments that are at this time hostile to the spread, even though everyone is on pins and needles.”
According to Tomback and other scientists, climate change is contributing to the expansion of the fungus. “Warmer temperatures are enabling spore transmission at higher elevations now, even at tree line and at the northern edge of whitebark pine range,” she said.
As absolute minimum temperatures in the West’s high mountain valleys have warmed — between six and 10 degrees Fahrenheit — and periods of extreme cold have declined in duration, the high country has also become more hospitable to mountain pine beetles, a native pest. The higher temperatures allow the beetles to persist through winters. In the spring, adults bore beneath the bark of whitebark pines and excavate grooves, called galleries, in which they lay their eggs. When the larvae emerge, they devour the tree’s cambium layer, killing the trees.
When whitebark pine forests decline, a signature ecosystem unravels, affecting habitat and food for an array of species
The Confederated Salish and Kootenai Tribes have seen major changes in the 105,000 acres of whitebark pine forest on their 1.3-million-acre reservation in western Montana. Since 2012, they have been working to save these forests by locating resilient whitebark specimens and then breeding and planting their offspring in their greenhouse. “There’s an urgency, definitely,” said ShiNaasha Pete, the tribal forester. “A good 75 percent is pretty wiped out. We have blister rust, but we also are fighting against fire. We’ve had fire at the higher elevation these past three years, and we lost habitat.”
When whitebark pine forests decline, a signature ecosystem unravels. “The whitebark pine is at the center of a web of biodiversity,” noted Tomback. “It provides ecosystem services because it grows under harsh conditions at the highest elevation, protecting snowpack and regulating downstream flow.”
Whitebark pine forests provide habitat for an array of species, including carnivores, birds, and small mammals, in addition to significant quantities of food. The pine produces a cranberry-size nut that is rich in fat and protein. Chickadees, nuthatches, Steller’s jays, crossbills, grosbeaks, woodpeckers, and a myriad of other birds eat those seeds.
The Clark’s nutcracker is the most well-known denizen of the whitebark pine ecosystem and is critical to the tree’s existence. Tomback has spent the last five decades studying the relationship between Clark’s nutcrackers and whitebark pine. The bird and tree, she says, have a mutualistic relationship. The bird gathers vast numbers of nuts and buries them far and wide for consumption throughout the winter. Caches contain from one to 14 nuts, and a single bird may bury as many as 98,000 in a single season. The nutcracker is renowned for its excellent spatial memory: It remembers where most of the nuts were buried. Those they forget, however, survive to become the next generation of whitebark pines.
But now, the relationship between Clark’s nutcrackers and whitebark pines appears to be breaking down. Bird populations have declined in some places as whitebark pine forests die. With fewer Clark’s nutcrackers caching fewer seeds, the tree has ever-fewer natural plantings — no other birds cache its seeds — further hastening the forest’s demise.
The loss of whitebark pine could also cause a decline in red squirrels that depend on the nuts, which they gather in piles of leaves and debris. A decline in squirrels could, in turn, affect carnivores that eat squirrels, including the Canada lynx, fox, and bears, which raid squirrel nut caches for a robust meal during hyperphagia, when they are preparing for hibernation.
Keeping the ecosystem intact, or restoring it where it has unraveled, will be a huge, long-term, and uncertain effort.
The trees are important to bears for other reasons. The nuts ripen in the fall, drawing bears out of populated areas and into the high country, where they are less likely to come into conflict with people. Research shows that the litters of bears that eat pine nuts have better survival rates.
Keeping this ecosystem intact, or restoring it where it has unraveled, will be a huge, long-term, and uncertain effort. “I would say its fifty-fifty,” said Noah Greenwald, the endangered species director for the Center for Biological Diversity, which is not involved in the project. Part of that is bureaucracy: the tree was first proposed for listing in 2008 yet was only listed by the Fish and Wildlife Service last year, thus slowing any restoration planning.
Another aspect is the high country’s rapidly changing environment. “I applaud the efforts,” Greenwald said. “But the scale is daunting. There is more potential for fire, and mountain hemlock is moving into the habitat. Fingers crossed.”
Despite the widespread dying of trees, Tomback believes the broad effort to grow and replant whitebark pine, the recent listing as threatened, and advancements in genetics give the species a fighting chance. “The fact that it has been listed, and we have so many people who care — there is hope for the future of whitebark pine,” she said. “There’s going to be a period of time, decades even, where we do not have whitebark pine ecosystems. It will go through a bottleneck, there’s no question. But I have confidence that we can keep it on the landscape indefinitely.”