WSU researcher investigates potential link between beetle outbreak in Yellowstone and climate changeOctober 6, 2008
Scientists may soon be closer to understanding the intricate connection between a large scale insect outbreak in Yellowstone National Park and global climate change, thanks to the work of one Wayne State researcher.
Dan Kashian, Ph. D., assistant professor of Biological Sciences in the College of Liberal Arts and Sciences, received a $306,296 grant from the National Institute of Climate Change Research in the Department of Energy to study how the current outbreak of mountain pine beetles in the Yellowstone region is altering carbon cycling in forests, and what effect this alteration may have on global climate change.
"This is a very critical question in the west right now, because there are huge bark beetle outbreaks all the way from British Columbia almost down to Mexico, and they're all happening at the same time," said Kashian, a resident of Brighton, Mich. "So it's not just one big outbreak, it's a synchronized set of big outbreaks, which is unprecedented."
Mountain pine beetles attack large, old growth trees and cause a slow death over two to three years, causing the trees' needles to turn bright red. There are several reasons these outbreaks are cause for alarm, Kashian explained. Trees killed by beetles have dead twigs and needles that are very flammable, and may create substantial fuel availability for wildfires. A second major aspect, and Kashian's focus, is the potential of these outbreaks to alter the rate of carbon cycling between the forest and the atmosphere, and the relationship of this cycle to climate change.
"Trees take up CO2 from the atmosphere as they grow, but release CO2 as they die and decay," Kashian said. "Anytime you're releasing carbon dioxide into the atmosphere, you're potentially contributing to climate change. Bugs are very tuned in to climate. If climate change leads to a warmer or drier climate that favors bark beetle populations, those bugs will kill more trees, which may accelerate the whole process."
In his study, Kashian will investigate whether climate changes that have already taken place have contributed to the current outbreaks, and how these outbreaks may factor into future climate change. "There could be a feedback between bugs killing trees and releasing CO2, CO2 further contributing to climate change, and then climate change allowing for more or more extensive insect outbreaks," he said. "It's just a vicious cycle."
Kashian will take inventory of the carbon stored in the forest using live and dead trees as well as soil samples at different locations throughout the region. Along with determining the amount of carbon lost, he will calculate the time required for the same amount of carbon to be recaptured though tree regrowth. The work is similar to a previous study in which Kashian determined the amount of carbon lost in the 1988 Yellowstone fires, a landmark event that burned 45 percent of the forest, would take 236 years to fully return. Data from Kashian's current study will be factored into his previous figure to determine how more frequent disturbances in Yellowstone's forests may exacerbate carbon released to the atmosphere.
The results of Kashian's research could contribute to the growing body of evidence of observable ecological impacts of climate change. The danger, however, is not in whether these beetle outbreaks occur, but whether they start occurring more frequently. "Fires and beetle outbreaks are natural to the ecosystem; they happen, they always have happened, and even though they may look ugly at any one point in time, the forests are actually adapted to it," Kashian said. "So my focus isn't on the fact that these disturbances occur, but on what would happen if they occurred more often - How much the amount of carbon released into the atmosphere would increase. I don't think anyone has considered that yet."
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