Starting about 2000, outbreaks of mountain pine beetles caused, in the words of the National Park Service, “considerable mortality” in the whitebark pine trees of the Greater Yellowstone Ecosystem.
The beetles killed whitebark pine trees across millions of acres in and around Yellowstone National Park.
University of Idaho researchers and their partners say in a new study that temperature increases caused by climate change were a major factor behind the outbreaks of mountain pine beetles.
The study, led by Polly Buotte, a postdoctoral researcher in the UI College of Science’s Department of Geography, is the first to pinpoint the multiple climate factors behind these outbreaks.
“By the middle of this century, most years will be as suitable for beetle outbreaks as in the 2000s. It’s where we’re headed,” Buotte said in a press release.
(Mostly healthy whitebark pines. Photo courtesy Polly Buotte)
(A whitebark pine killed by Mountain Pine Beetles. Photo courtesy Polly Buotte)
(Buotte said, “This is a pitch tube, where a WBP tried to eject a beetle with pitch flow. This tree died and the small holes with no pitch are the emergence holes from the adult beetles that were laid as eggs in this tree.” Photo courtesy Polly Buotte)
The goal of the study is to help forest managers protect whitebark pines in the future, as temperatures climb due to climate change.
According to the researchers:
- The strongest influence was warmer winter minimum temperatures. Buotte said that in previous decades, researchers thought whitebark pines grew at high enough elevations for beetles to freeze and die every winter. But with the absence of very low winter temperatures after 1992, more beetles survived. This effect was a result of climate change that occurred in recent decades.
- Another influence was higher average fall temperatures. Warmer falls synchronize beetle populations, so they all hatch and emerge to infest other trees at the same time. These temperatures were not tied to climate change in recent decades.
- Finally, lower summer precipitation levels and warming led to drought-stressed trees that were more susceptible to beetle infestation.
- The researchers also created a model showing the potential for beetle attacks in coming decades and found that projected future climate change will continue to lead to conditions favorable to outbreaks.
“This adds pretty strong evidence for the need to include climate as a consideration for managing whitebark pine,” Jeffrey Hicke, a UI associate professor of geography, said in the press release.
The National Park Service says the Whitebark Pine is important because “it retains snow and reduces erosion, acts as a nurse plant for other subalpine species, and produces seeds that are an important food for grizzly bears and other wildlife.”
Buotte and Hicke said that planning for potential beetle outbreaks is vital to the success of efforts to preserve the whitebark pine in the Greater Yellowstone Area.
UI associate professor of geography John Abatzoglou also contributed to this research, which you can see at the link below.
The study, which was supported by the Northwest Climate Science Center, included researchers from the USDA Forest Service and the University of Wisconsin, Madison.
National Park Service information on the Whitebark Pine:
Northwest Climate Science Center:
Posted August 29, 2016.