FRISCO — Colorado’s verdant high country spruce and fir forests get all the glory on the cover of tourist brochures, but the state’s most widespread forests by far are the scruffy piñon-juniper woodlands that once grew on more than 5 million acres on the west slope of the Rockies, across the Colorado Plateau and out into the Great Basin.
Forests in the high country and along the Front Range are already making a comeback from the bark beetle infestation, but on the windswept mesas in the Four Corners region, it’s a different story. In Colorado’s forgotten forests the ips beetle outbreak of the early 2000s killed up to 80 percent of all piñons in the hardest-hit areas. And in the new climate regime — consistently warmer and drier — the trees just aren’t growing back.
“In lower elevation places with less moisture, there’s not much regeneration because the forest lost a lot of seed stock,” said Tom Mask, a Gunnison-based Forest Service entomologist who studied the ips beetle outbreak.
It’s unclear when — or if — piñons will make a comeback in those drier lowlands, Mask said, adding that the Forest Service budget hasn’t enabled researchers to closely monitor recovery of the Southwest’s iconic forests. With bark beetle populations exploding around the same time as the ips beetle outbreak, attention and money were focused on dying forests around Aspen, Breckenridge and Vail, with little thought to the piñon-juniper highlands of the Four Corners.
Consider the humble piñon. It may not be as tall or graceful as a towering spruce, and doesn’t offer the rustling shade of an aspen grove, but the bushy evergreens are cultural and ecological touchstones. They grew, until recently, where few other trees could survive and they produce exceptionally large and nutritious seeds, providing sustenance for humans and animals in an arid region where finding food doesn’t come easy.
For centuries, nomadic bands of Native Americans relied on piñon pine nuts as a staple in their winter diets, traveling hundreds of miles across the Great Basin (from western Colorado to eastern California) to set up fall camps where the trees were producing plenty of nuts. Not every stand of trees produces nuts each year, so the tribes had to rely on cultural knowledge passed down orally through generations, as well as long-range scouting parties to find the most productive areas. In years when they failed to find a good harvest, winter starvation ensued.
Today, the nut is still a staple in some quarters. During the harvest, “piñones” signs draw flocks of eager cooks to trucks and roadside stands along the highways in Colorado and New Mexico.
The wildlife landscape of southwestern Colorado would also look quite different were it not for piñons. Small birds and small mammals all rely on the nuts, in turn providing food for larger predators. Spreading out from their squat trunks into thick, low-slung crowns, the trees literally provide shady microclimates, where all sorts of critters can ride out the heat of the day, then sortie out in the cool of dawn and dusk to find water or search for a mate.
But all that is about to change in southwestern Colorado, where a human-caused global warming may well wipe out a tree species that previously survived eons of gradual climate change.
No seeds, no trees
“To regenerate piñon, all the stars have to line up. They only sprout if they have enough moisture … it’s kind of an involved process to get regeneration,” said Tom Eager, another Gunnison-based Forest Service researcher who worked with Mask on studying the ips beetle invasion. There have to be birds to move the seeds around, creating caches that can sprout into new stands, given enough moisture. And it partly depends on what kind of seed source was there to begin with, Eager said.
Soon, that seed source may no longer exist, according to University of Colorado researcher Miranda Redmond, who took a close look at piñon pine seed formation a couple of years ago. Warmer temperatures are inhibiting seed formation in many areas. That means there’s nothing with which to start a new forest, short of active human intervention, which is highly unlikely, given the continued budget woes of land management agencies like the U.S. Forest Service.
“In area with really high mortality, there’s not much regeneration. In areas with low mortality, we saw more … especially where there is good shrub cover, with a shading effect,” Redmond said. Those areas may have more organic matter in the soil, which holds moisture better than the dry mineral dust of most desert soils, she said, explaining how desert trees and shrubs build up their own microclimates in the soil by piling up organic materials: Tiny pine needles, leaves, grasses and bits of bark and branches that could nurture a sprouting seed.
But the areas that were hit hardest by the beetles are the same areas hammered by heat and drought, steadily turning the Southwest’s woodlands into desert. Redmond’s research shows that that warming temperatures at higher elevations are preventing seed formation, which is spurred, she believes, by the onset of cool weather in the late summer. As the climate regime in the Southwest changes, those autumn cold snaps are becoming less frequent, resulting in less piñon regeneration — no seeds equals no new trees.
The intense and extensive ips beetle outbreak sparked concerns at the time. But the bark beetle epidemic in lodgepoles was also starting to peak, affecting more densely populated regions, as well as critical watersheds and areas with high-value recreation developments, so the vast reaches of piñon-juniper became Colorado’s forgotten forest.
The mountain pine beetle outbreak was tracked and mapped acre by acre; politicians banged their drums to demand funding for forest treatments, and the Forest Service established a high-level task force to tackle the outbreak. By contrast, it’s hard to get a good sense of the total acreage affected by ips beetles — even though piñon-juniper is the largest forest type (about 5.5 million acres) in Colorado.
The most recent information provided by the Forest Service dates back to the mid-2000s and indicates that ips beetles killed slightly more than 2 million acres of piñon-juniper in Colorado alone, with additional acreage affected in New Mexico, Utah, Arizona and even as far west as Nevada.
CSU professor Bill Jacobi estimated a similar mortality after doing some research in the area. Overall, ips beetles may have killed 30 percent of all the piñon pines in the Four Corners region, and a much higher percentage at lower elevations he said.
Detailed forest data from 20 years ago — before the ips beetle outbreak — enables researchers to make good comparisons between what was there then and what’s left after the beetle. But the warmer and drier than normal climate in the past 10 years means all bets are off when it comes to regrowth, Jacobi said.
In many areas, piñon pines are probably gone for good. In some cases, they may replaced by junipers, which can tolerate warmer and drier conditions. That could benefit a few animals that prefer juniper, but the shift will displace a host of species that for eons have depended on piñons, a sure sign of climate change in the Four Corners region.
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[ Dying and dead piñon pines are changing the landscape at Colorado National Monument. @bberwyn photo ]