There are millions of dead trees in Colorado’s forests. Tree mortality is at one-fifth over the last two decades. Forests with lots of dead trees are at a greater risk for worse wildfires. Carbon is also moving to the atmosphere, from out of the carbon sink that is the forest. The Colorado State Forest Service is the main force in mitigating potential bark beetle epidemics.
Mountain pine beetles are bark beetles that infest ponderosa, lodgepole and limber pine trees. One year is a typical generation, from July to August. It is becoming more common that two generations happen in a year and the population growth becomes exponential. The needles turn red after turning yellow red and drop the second year of infestation. Pitch tubes and boring dust are also signs a tree is infested. Thinning, promoting tree age and species diversity is the best way to promote tree health. Insecticides, trapping and solar treatments are other management tools.
Spruce beetles are bark beetles that infest Engelmann and blue spruce trees. They typically produce a generation every two years. Adults fly for a new host late May to July. They mostly infect at elevations of 9000 feet and above.
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Over the last 20 years, mountain pine beetles caused the highest mortality, impacting 3.4 million acres in Colorado. They mostly infested trees from 2004 to 2011, with over 1000 thousand acres being affected in 2008. While spruce beetles only impacted 1.78 million acres in the last 20 years, they are more current. Mountain pine beetles infestations are at an all time low with less than 900 acres being affected in 2017, and spruce beetles started to infect in 2001. They have increased nearly every year, with over 400 thousand acres being affected in 2014.
Temperature and precipitation affects forest insect populations. The statewide annual temperature over the last 20 years is two degrees F warmer from 2017. As well as 2 more inches of water. For the sixth year in a row, the most damaging forest insect was the spruce beetle. 206,000 acres had active infestations, 67,000 of which were new in 2017.
The grizzly bear’s diet may have to change. The mountain pine beetle usually targets mid latitude lodgepole and ponderosa pines. But since the 1970s it has gotten warmer and as a result has been killing whitebark pines in the Rockies. These pine trees feed birds, squirrels and grizzly bears. Six hundred or so grizzly bears live in Yellowstone, increasing 4 to 7 percent each year.
Grizzly bears in yellowstone don’t concede to the notion that all grizzly bears are omnivores. In early spring they eat elk and bison calves. In late spring and summer they eat cutthroat trout from the rivers. They eat roots as well, but head up higher, turning to moths and pine nuts. They can eat up to 40,000 cutworm moths in a day. But they mostly depend on whitebark pines, they are the most important fattening food available to grizzlies in late summer and fall.
Colorado state forestry officials say that the majority of Colorado’s large-diameter lodgepole pine forests will be dead within 3 to 5 years. Areas with dead trees will see worse fires for the next 15 to 20 years. In boulder and Larimer counties, there was a 1,500 percent increase in beetle activity in the last year.
Twenty-two million acres of Canada’s trees were ravaged by pine beetles, then they moved south. One and a half million acres of forest land in Colorado have been eaten, about 70% of all the state’s lodgepole pines. Within the next few years, the entire population will be wiped out, leaving deforestation the size of Rhode Island. The beatles are less picky than before, getting small trees first. What has happened since the 2000s in a perfect storm. There has been drought conditions and decades of fire suppression. Many lodgepole pines are over 80 years old, making them more susceptible.
It isn’t all bad though. Bird populations are finding new homes from fallen trees and thrive. An 18,000 square-foot wood-pellet plant just opened, providing wood pellets. These heat stoves and increasing energy costs. These trees may even be turned into ethanol.
A third of Colorado’s 100 sawmills use beetle killed trees for wood. Twelve hundred truckers and millworkers have jobs because of the forest product industry. They make 86 million dollars worth of products yearly. In Eagle County, wood goes to a biomass plant that uses dead trees for electricity. Colorado’s lumber industry isn’t big enough to process all the dead trees that need to be cleared.
The beatles will continue to kill. Once a tree shows signs of infestation, it’s already long dead. Chemical treatments may work, but cost $50 per tree, making it uneconomical. Clear cutting is the simplest solution.
The Hayman fire left a 50,000 acre hole. A fraction of the area was reseeded, but trees have not grown back and aren’t expected to for centuries. The heat sterilizes soil, destroying all biomass across wide areas, creating gaps that can’t be reseeded easily. Researches search for drought adapted species and genotypes to control evaporation.
Mountain pine beetle infestations are turning forests into a new source of greenhouse gases. The decaying trees are releasing carbon into the atmosphere. The main way to fix this problem is to log out most of the dead trees and plant new ones as soon as possible.
In Boulder, tiny predator wasps were imported from China in 2015. They released 200 a week from June to July. The Oobius agrili wasps pierce beetle eggs and lay their own eggs inside.
Southwest Colorado is under threat from beetles as well. Almost 10% of the forest area in San Juan forest has been infested since 2011. They used to kill trees for 2 years, then dissipate the third year. The drought may be to blame, weakening trees and preventing them from pushing the beetles out. Four thousand acres of timber is ready to be sold if a mill is interested.
Bibliography
- “2017 Report on The Health of Colorado’s Forests.” Csfs.olostate.edu, csfs.colostate.edu/media/sites/22/2018/01/2017_ForestHealthReport_FINAL.pdf.
- Pankratz, Howard. “Beetle-Kill Rate in Colorado ‘Catastrophic.’” The Denver Post, The Denver Post, 7 May 2016, www.denverpost.com/2008/01/14/beetle-kill-rate-in-colorado-catastrophic/.
