As the glow from our car’s headlights flows over the colorful walls of the roadside canyon, Leo, Mary, and I discuss whether to abandon today’s planned hike to the summit of Sepulcher Mountain. Haze from distant fires has infiltrated Yellowstone and will obscure the view from the 9,646-foot summit. But summer is flying by, and we may not get another shot at it. We pull into the Glen Creek trailhead, don jackets against the morning chill, and start walking north as the sun sneaks over Terrace Mountain.
We are heading for the land of whitebark pine, the tree that dominates Yellowstone’s landscape above 8,500 feet. Once there we will find evidence of a threat to the whitebark and Yellowstone. A disaster brought on by a beetle about the size of a grain of rice. An insect blight that may be the largest ever witnessed in North America. An epidemic that humans near and far helped cause.
Before we’ve gone a quarter mile, we hear a howl behind us. “That’s a wolf!” says Leo. We stop dead in our tracks and turn to face the direction of the howl. We and the wolf are silent for a moment, and then another howl arrives. Without a word, the three of us run up a small rise in the direction of the howl, hoping for a glimpse. Atop the rise we stop, our panting the only sound. Then comes a yipping.
“That’s coyotes,” Mary says as more yips create a chorus.
“Do you think the first one was a wolf?” Leo asks.
“Could the first have been a wolf and then the coyotes replied?” I wonder aloud.
On some other morning we would wait and watch and answer our questions. That’s how our hikes become meanders and how we have come to call ourselves “meanderthals.” But this is not our usual meander; it’s a twelve-mile hike, with a car shuttle at the end. Leaving the questions unanswered, we turn away and proceed across the edge of Swan Flat. After the trail starts uphill, we ascend to the large golden meadow that we will follow to the top. In the distance, on a ridge descending from the peak, we see a herd of elk. Through binoculars, Mary observes that the elk have spotted us, gathered, and started moving up and over the ridge past a large aspen grove.
We stand silent for a few moments, admiring and imagining, and then Leo points and whispers emphatically, “Look over there. That’s a grizzly!” We watch the grizzly climb the ridge the elk vacated. At the top, the bear lumbers along the ridge, and then, sadly for us, disappears down the other side. “That’s the perfect way to see a grizzly,” Leo says, “distant and safe.”
As we continue upward, the switchbacks across the meadow grow shorter and steeper. We stop to catch our breath and Leo points to a stand of nearby trees, some dead with skeletal branches silhouetted against sun and haze, others thick, green, and bushy. “Those are whitebark pine,” he says.
Mary and I look where he’s pointing as he adds, “Listen to the Clark’s nutcrackers in there. It’s almost like something out of Alfred Hitchcock’s The Birds. They love whitebark pine nuts.”
Near the top of Sepulcher, the trail enters a whitebark pine forest, an eerie place where life and death mingle. Leo says this is a perfect location for a grizzly daybed. He stops beside a lush whitebark, squats down below the lowest limbs, and declares, “Oh, look at this. Here’s one. See how it has been cleared out in there. And the multiple exits. I’ll bet this is a daybed.” While I’m excited by this find, I can’t help but wonder at the wisdom of poking around a grizzly’s bedroom.
We climb the last stretch and reach a jumble of huge volcanic rocks at the peak. As we clamber among the rocks, I spot a golden-mantled ground squirrel scampering up one, its mouth filled with a whitebark pine cone and its eyes on us. It follows a crack to the top of the boulder and with a disdainful flick of its tail, disappears over the other side.
The squirrel’s presence reminds me to look around on the ground, and I discover several areas where that squirrel or others have been dining. Pine cones stripped of their seeds lie on a rock, surrounded by cone debris and clumps of the whitebark’s needles with their distinctive groups of five.
The whitebark pines that surround us grow slowly and live long. The oldest documented whitebark survived a thousand years. In Yellowstone, the tree takes 75 to 100 years to begin bearing cones. And all around us, all around Yellowstone, these trees are falling to the mountain pine beetle.
The beetle is a native insect and has travelled north with the pines that have colonized the Rocky Mountains, according to Jesse Logan and William MacFarlane in a journal article. The problem with the insect—as far as the whitebark pine is concerned—is that beetles reproduce by drilling a hole in the tree all the way to the phloem, the layer that carries the tree’s nutrients, and then they lay eggs. Once the invaders drill enough holes, the pine can’t get nutrients through the riddled phloem and dies.
But the whitebark fights for its life, say the authors. The trees try to halt the beetle invasion by producing more resin. The beetles counter by introducing a fungi that not only overcomes the trees defenses but also feeds the beetles’ offspring, a one-two punch that’s life-sustaining for the beetle and deadly for the pine.
Though this battle between pine and beetle is natural, Logan and MacFarlane say that humans have given the beetle the advantage. As human-caused climate warming raises winter temperatures in Yellowstone, more beetles survive winter. As summer temperatures warm a few degrees, the beetles can complete an entire life cycle in one year. With warmer temperatures all year, the beetles die less and produce more. The result: an outbreak of mountain pine beetles that has spread further and killed more whitebark than scientists thought possible.
Why does the death of whitebark pines matter? Because, say the authors, the whitebark is a keystone species, critical to the entire ecosystem and its occupants.
Let’s start with that invisible chorus of birds in the pines we passed on our way to the summit. Those Clark’s nutcrackers feed on and assist whitebark pine. The tree’s cones are tightly closed and must be torn apart by nutcrackers, which then bury hordes of seeds in scattered caches where they hope to feed later in the year. But the birds don’t find all their buried treasure. And seeds not eaten can sprout, replenishing and expanding the forest. The Clark’s nutcracker is the Johnny Appleseed of the whitebark pine forests.
Nutcrackers aren’t the only animals hungry for the pine’s seeds. Squirrels, like that one I saw near the boulders, trash the cones and stockpile seeds beneath the pines. Those mounds attract grizzlies. That grizzly that we saw go over the ridge may have been searching up here for some squirrel’s stash. The pine’s fatty seeds are critical to female bears before they enter their winter dens in just a few weeks. The health of her developing cubs can be determined by the amount of pine seeds she consumes before hibernating. Reduce the pine seed intake and you reduce the cub survival rate and the grizzly population.
Elk benefit from whitebark pine, too. When elk calve amongst these trees in spring or early summer, the forests protect them from harsh weather and hungry predators.
Finally, say Logan and MacFarlane, we humans benefit. Most of the water in western rivers comes from winter and spring snows. Whitebark pine forests shelter snowfall from the wind and shade it from the sun. The snow takes longer to melt and gives us a prolonged, consistent, flow of precious water.
Thus, as the whitebark pine goes so does the Greater Yellowstone Ecosystem (GYE). This leads to a troubling question: How likely is it that whitebark pine forests will succumb to the beetle and stop providing critical ecological benefits?
The answer is unclear. Logan and MacFarlane state, “A disturbance of this magnitude in whitebark pine is unprecedented in the ecological history of the GYE.” They speculate that the pine may not be able to adapt its way out of danger. But they respect the tree: “Whitebark pine is a tough species that has evolved to withstand some of the harshest environmental conditions on the planet.”
The battle shows no sign of abating, and only time will reveal the outcome. Meanwhile we must learn to live with large dead whitebark pine forests. And we must learn to accept our part in their demise and work to correct human-caused climate warming.
This whitebark pine ecosystem we have explored amazes and saddens me. I’m glad that the smoky haze diminished the views today. Had this been a typical Yellowstone blue-sky day, we would have been dazzled by the 360-degree view of mountains and may have missed the evidence of the battle between beetles and pines. This battle reminds me again that no matter how massive and rugged Yellowstone appears, this wonderland teeming with wolves and coyotes, elk and grizzly, squirrels and nutcrackers—and mountain pine beetles—is a delicate ecosystem that humans living nearby and far away can change in destructive and permanent ways.
Comments? Questions? I welcome your feedback. Email me at firstname.lastname@example.org
To read my previous post about Yellowstone’s grizzlies
Rick Lamplugh lives near the north gate of Yellowstone and is the author of the Amazon Bestseller In the Temple of Wolves: A Winter’s Immersion in Wild Yellowstone. Available as eBook or paperback. Or as a signed copy from the author.