Whitebark pine trees are found in cold, windy, high elevation areas in western North America. It's a relatively hardy species of tree, known for being one of the first plants to establish in an area after it's been disturbed, like by a fire. But the species is under attack from mountain pine beetles and a non-native fungus known as white pine blister rust that slowly damages and eventually kills trees.
"Usually it's more not that the blister rust directly kills the tree, the tree just spends so much energy fighting it," said Avery Beyer, a forester on the Caribou-Targhee National Forest Timber Management System that straddles Idaho and Wyoming. "And many of them are like whitebark pine, which live up high in the mountains, don't have a lot of excess energy, so to speak. They live in a harsh environment with a very short growing season, poor soil, limited availability to water."
Currently, there's very little that can be done to combat the fungus. Those trees that are infected with blister rust can become more susceptible to attacks from pine beetles.
But some trees appear to be dealing with blister rust much better than others. So foresters are undertaking a huge effort to help those trees multiply. So far, there are only a few hundred of these apparently resistant trees that have been found.
"And we find trees that had been infected and look like they've been infected for a long time, but the infection has still remained localized in the initial infection site," said Beyer. "So instead of a tree that looks like it's dying, usually you can find one really old canker, and then four or five slightly younger cankers, and 15 or 20, even younger cankers - the tree just keeps reinfecting itself. If you find a tree that was infected once a long time ago, it doesn't appear to have gotten a lot worse or more infection, you're like 'hm, that tree seems to be resisting it.'"
Once these trees are identified, foresters take action. Whitebark pine don't produce cones until they're around 50 years old. So if the resistant tree is producing cones, foresters collect them, year after year. These cones are taken back to a nursery where the seeds are collected and planted or collected and stored for later planting.
He said they also will help manually spread pollen from resistant trees to other resistant trees, giving the cones next year a higher chance of producing resistant seedlings.
"In fact, slowly they dial in which trees really appear to be resistant and which ones maybe are less resistant, and are not getting infected maybe more due to specific location things. Over many, many, many years of doing that we have trees that we have a pretty good idea of how resistant they are," Beyer said.
If the resistant tree isn't old enough to produce cones yet, foresters can still use it. They collect branches and bring them back to the nursery. There, the branches are carefully grafted onto the rootstock of an older tree, essentially tricking the branch into thinking it's an older tree. These trees will then produce cones that the foresters can use sooner.
"So that hopefully in the future, instead of having to go collect cones from the widely scattered trees that we can do collections, from these nurseries where we know there's been soil, we had irrigation, they're protected from fires and beetles and whatnot," said Beyer.
Whitebark pine are incredibly important to the surrounding wildlife like Clark's nutcracker, squirrels, and grizzlies which feed on the large, highly nutritious seeds. They're also important for humans. Their shade keeps snowpack from melting longer into the spring, which feeds alpine streams and waters nearby plants.
"And the trees are not dying quickly, by and large. It isn't killing them overnight. Trees can be infected with blisters and survive for a dozen or more years. So this is a long term threat," said Beyer. "But ultimately, it affects people in the West's life because it affects how our mountains retain water, which then affects our ability for agriculture, for drinking water, and all that stuff ultimately. So you have something you don't in your day-to-day life see, it will have an impact on you if things change dramatically."
The species is now under consideration to be listed as "threatened," an effort that has been decades in the making. But Beyer says the listing may not be the silver bullet some hope it will be.
"We're trying to see how much it's changing or if it's at a stasis. The sum total of all these threats has brought the numbers way down, but it seems to be holding its own from this point on. Ultimately, what will listing do to change it? I mean, it puts it out there that this happens, and then people are more aware of it. And so ultimately, there's that, which is a positive. But we're not going to remove blister rust from the landscape. It's been in the world here for 100 years now. It's widespread. It's not going anywhere. Mountain pine beetles, climate change, fires, threats to forests. How much is that going to change is unknown."
Have a question about this story? Contact the reporter, Ivy Engel, at iengel@uwyo.edu.
