Mountain pine beetles like the dry warmer temperatures and it just so happens, Colorado had that type of year in 2012. This means big trouble for pine trees, according to new research from the University of Colorado.
A research team led by CU doctoral student Teresa Chapman studied the correlation between Colorado’s recent wildfires and the pine beetle epidemic that previously killed trees in those burn areas. The team found being in a drought condition, paired up with warmer temperatures, has the bark beetle in an extreme epidemic.
Chapman explained that in these conditions, trees are unable to produce resin, the hydrocarbon that helps them ward off the insects. “Warmer temperatures already favor the beetles, and coupled with the extreme drought of 2001-02, the trees were not able to defend themselves,” Chapman said.
“This study confirms that warming temperatures and drought are likely triggers of the widespread bark beetle outbreaks that have devastated forests over vast areas of the West,” confirmed Richard Inouye, program director in NSF’s Division of Environmental Biology. “It also suggests why bark beetle outbreaks may vary for two different tree species,” he said, “and how different forests may be more or less susceptible to these insects that are transforming mountain landscapes.”
Mountain pine beetles are around the size of rice grains, and adult females lay their eggs in the bark of trees. When the larvae hatch, they spend about 10 months feeding underneath the bark before developing into adults and attacking other trees. The pine beetles disrupt the circulation of trees, which essentially starves the tree to death.
The mountain pine beetles have been found in a range from Canada to Mexico and are at sea level, all the way up to 11,000 feet. These bark beetles have shaped the forests by attacking the old weak and sick trees.
“In recent years some researchers have thought the pine beetle outbreak in the Southern Rocky Mountains might have started in one place and spread from there,” said Chapman. “What we found was that the mountain pine beetle outbreak originated in many locations. The idea that the outbreak spread from multiple places, then coalesced and continued spreading, really highlights the importance of the broad-scale drivers of the pine beetle epidemic, like climate and drought.”
The study suggests that under the current warmer climate change, the spread of the bark beetle in ponderosa pines is likely to grow until the food source is depleted. “Given the current outbreak of mountain pine beetles on the Front Range, the effect on ponderosa pines is certainly something that needs further study,” said Chapman.
A paper on the subject is published in the current issue of the journal Ecology. Chapman is lead author of the paper; co-authors include CU-Boulder scientists Thomas Veblen and Tania Schoennagel.
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