Bark beetles devastate large forests | TahoeDailyTribune.com

Bark beetles devastate large forests

Fred Roberts
Special to the Tribune

Forest dwellers, especially those in more distant times, probably considered their beloved forest home as permanent. Our forests of Western North America, with their imposing and abundant sequoias, cedars, pines, spruce, and hemlocks impart a stately permanence to those of us who are their current forest dwellers. Sure, logging, forest fires and forest insect outbreaks might shake our confidence a bit, but we still hold onto that cherished image of permanence. After all, the western forests are vast and they are managed by highly trained professional foresters. And, for those of us who need to connect deeply to these forests, there are many locations, Tahoe being one, where we can still hike, ski, walk and live among the trees, finding that sought-after relief from urban chaos. That is until recently. In the past two decades, bark beetles, those unlikely almost microscopic creatures, have broken free of many natural constraints and have devastated forests at unprecedented levels across the west.

Andrew Nikiforuk, in his book “Empire of the Beetle,” recounts the personal anguish and grief of a number of Alaskans in the 1990s who lost their forest surroundings to the beetle. Some complained that they now lived in a stump farm. This scenario has been repeated more recently in British Columbia, Colorado, Montana, Idaho, Arizona, New Mexico and Utah. Nikifouk suggests that the causes can be traced to out-of-control logging, bad public policy, fire suppression and climate change. The question for us is, can it happen in Tahoe?

The Tahoe forests have a few species of bark beetles that kill trees under normal forest conditions. These beetles have coevolved with the forest trees for millions of years to find their niche as forest managers. They act as agents of forest renewal by killing old and weakened trees. Sometimes they will kill healthy stands of trees when conditions fuel their reproduction. One such condition is when a forest is composed of a preponderance of even-aged trees approaching senility at the same time. Much of the forests of the Tahoe basin are dominated by even-aged trees because the forests were clear-cut in the 1800s. Another condition that has been instrumental in the killing of vast forests in British Columbia is the increase in temperature due to climate change. The beetles complete their life cycle faster as temperatures increase and beetle mortality is reduced as winter low temperatures increase. A more refined question might be to ask whether the forest conditions in Tahoe are rife for a beetle outbreak.

Tahoe students and residents are going to be given a chance to better understand bark beetle dynamics in the Tahoe Basin on July 25, when Joel M. Egan, forest entomologist with the U.S. Forest Service in Missoula, Mont., will give a talk on Bark Beetles. The talk will take place 6 p.m. in the Aspen Room at Lake Tahoe Community College. He will give an overview of the recent outbreaks of the beetles in the west, describe the amazing life cycle of the beetles, and then focus on an outbreak of Jeffrey Pine Beetle in the 1990s near Spooner Summit. The talk is sponsored by the science Club of Lake Tahoe Community College.

– Fred Roberts is a biology teacher at Lake Tahoe Community College.


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