Are Southern Utah’s high-elevation forests still at risk of a large bark beetle outbreak?

ST. GEORGE — Across the Markagunt Plateau, a volcanic field in Southern Utah, “skeleton trees,” killed by bark beetles in the mid-1990s and early 2,000s, stand tall and bare against the mountain sky. In many areas, saplings bring new life to the devastated landscape.

This file photo shows a stump covered in gallery carvings caused by bark beetles, Duck Creek, Utah July 7, 2021 | Photo by Alysha Lundgren, St. George News

The forest is regenerating, but is it still at risk?

Jesse Morris, a research professor at the University of Utah who has worked in and around the higher elevations of Southern Utah for nearly 20 years said forests throughout Central and Southern Utah were “absolutely hammered” by bark beetles beginning in about 1997 until the early 2010s.

The tree species most impacted in the forests surrounding Cedar Breaks National Monument and Brian Head was the Englemann Spruce.

The spruce beetle epidemic killed over half the mature trees at Cedar Breaks National Monument and nearby Dixie National Forest, according to the Utah Office of Tourism.

“(It added) even more unique color and texture to this fascinating environment,” the site states. “The Alpine Pond Trail takes you through a ghost forest of dead spruce offering views of the amphitheater framed by the skeleton trees.”

Low-level, or endemic beetles from Southern Utah’s native population can be found in trees killed through various other means, such as old age and drought. But, these insects will also infest live trees, according to this informational document from the National Park Service.

“If there are only a few attackers, healthy trees can keep insects from boring into vital parts by flooding holes with gooey sap,” the document states. “When trees are too weak or devoid of moisture to ‘pitch-out’ a beetle, the insects begin carving into living tissue under the bark.”

This file photo shows dead trees at Cedar Breaks National Monument, Utah, Aug. 26, 2022 | Photo by Alysha Lundgren, St. George News

While many scientists believe that bark beetle infestations are natural and directly result from “the combined effects of changing forest health, climate and the beetle’s natural life cycle,” there are three factors that can create conditions favoring outbreaks that harm or kill trees.

These include changing forests, a changing climate and changes to the insects’ life cycle, according to the document.

Trees can be weakened by long-term drought conditions. Additionally, wildfire suppression can lead to an “unnaturally dense forest,” which forces trees to compete for resources, the document states.

The resulting weakened tree stands are more easily felled by strong winds, “creating large areas of downed logs — perfect for nesting beetles.”

Rising temperatures due to climate change are expected to cause a “considerable ecosystem change” on the Markagunt Plateau, according to the document.

To survive temperature extremes, most beetles go dormant for periods of time that are “driven by endocrine signals and environmental cues,” the document states.

Climate change impacts when this dormant period is triggered, causing bark beetles to grow and reproduce at a higher rate and “potentially doubling their population and their impact on the forest.”

A group of spruce beetles, date and location not specified | Photo courtesy of Jacques Regad, Département de la Santé des Forêts, France, CC BY 3.0,https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons, St. George News

“As environmental conditions ripen, beetles begin attacking living trees,” the document states. “If many weak trees are present, beetles emit a pheromone that alerts others in the area to swarm. This is how large outbreaks are triggered.”

Bark beetle outbreaks have caused “substantial changes in landscape structure and function,” which can also impact people living nearby, according to a 2018 study conducted by Morris et al.

“The effects of bark beetle outbreaks are often detrimental to the provision of ecosystem services, including degraded landscape aesthetics and diminished air and water quality,” the study states. “However, there have been instances where bark beetle outbreaks have benefited communities.”

For instance, while bark beetle outbreaks generally lower property values due to “a perceived reduction in the attractiveness of the affected landscapes” and the increased risk of falling trees, among other factors, the study reports that other properties saw an increase in value.

Homes located in dispersed rural communities could increase in value resulting from aesthetic factors, like improved views. For instance, homes on Alaska’s Kenai Peninsula saw a net real estate value increase of about $6,000 because of “better views” and “successional transitions” to tree species homeowners found more aesthetically appealing, the study states.

This file photo shows dead evergreens near Brian Head, Utah, July 7, 2021 | Photo by Alysha Lundgren, St. George News

Additionally, increases in sunlight, water and nutrient availability promoted the growth of understory grasses in some areas, “improving forage for animals and enhancing wildlife viewing and hunting opportunities.” This could also increase property values, according to the study.

In other cases, landscape aesthetics are adversely affected and could be a concern for the outdoor recreation industry as it could influence “the quality of visitor experiences” and how often recreators return to these areas.

The study references research conducted in Colorado and Wyoming, surveying visitors to three national forests, which found that aesthetics and recreational opportunities were the most important considerations for those who participated.

“Landscape aesthetics and the perception of a ‘natural’ environment are important attractors for outdoor visitors; the appearance of surrounding landscapes is therefore valuable to communities that rely on revenues generated by nature-based tourism,” the study states.

Additionally, beetle-killed stands can increase fire risk, depending on the state of the trees, St. George News previously reported. Where red or yellow needles are still attached, there is a higher risk of high-intensity canopy fires.

The risk is reduced when the needles drop but increases again when the tree falls to the forest floor.

This file photo shows dead needles on a conifer tree, Cedar Breaks National Park, Utah, Aug. 26, 2022 | Photo by Alysha Lundgren, St. George News

Due to the various impacts, land managers are working to develop strategies to suppress bark beetle outbreaks and restore affected ecosystems in some cases, the study states.

Many of the affected forests, including on the Markagunt Plateau, are beginning to regenerate, Morris said. And many of the spruce trees are too small in diameter to sustain another large bark beetle outbreak.

Saplings that are about 10 centimeters or less in diameter can’t provide enough nutrition to sustain the beetle’s reproductive cycles, he added.

“It’s kind of a sweet spot where they’re not susceptible to another infestation,” he said. “At least for spruces.”

As the forest regenerates and the trees mature, it may be at risk for another outbreak, which Morris said could take 60 years – possibly less. Other areas, particularly in lower elevations, that were not previously affected or that have been regenerating longer may be at higher risk.

To learn more about bark beetles and their impact on humans and ecosystems, click here to read “Bark Beetles as Agents of Change in Social-Ecological Systems.”

Copyright St. George News, SaintGeorgeUtah.com LLC, 2022, all rights reserved.

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