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Mountain Pine Beetles are Turning Up the Heat on Climate Change

Christine Wilcox

Posted December 5, 2012

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The mountain pine beetle infestations of the past decade are a clear and tangible demonstration of climate change, and they have resulted in widespread pine tree deaths across the western U.S.  A new article published last week is now indicating that the beetles are also involved in a dangerous feedback loop of increasing temperatures in the forests they attack, particularly in the summer.  Holly Maness and her colleagues at UC Berkeley have been studying pine forests in British Columbia, and their research shows that following the widespread die-off of pine trees due to beetle infestations, there is a measurable and significant decrease in the cooling effect those trees previously had in the forest.  This loss of evaporative cooling by the trees has resulted in a 1 degree Celsius increase in the summertime temperature of these dying forests compared to other nearby healthy forests.


Although this temperature difference might seem small, climatologists and other scientists studying global warming have emphasized that this type of change – which is not a result of background fluctuations over time – can have widespread detrimental effects.  For instance, there is concern that cloud formation and flood risk will increase in this area.  More research will help elucidate what other impacts this temperature feedback loop is having on these forests.  And while this research is focused on forests in British Columbia, it begs the question:  what similar climactic changes are happening in other beetle-killed forests like those in Yellowstone and the Northern Rockies?

We already know that 70% of the whitebark pine trees in and around the Greater Yellowstone Ecosystem have been lost to mountain pine beetles and another 25% were observed to be in earlier stages of infestation. This high-elevation pine tree used to be out of the beetles' reach, but as winter temperatures have climbed higher on average, the beetles have been able to move higher in elevation, survive over winter and even reproduce more quickly.  When whitebark pine is healthy, it serves many important ecological roles including stabilizing soil, and regulating snow-melt and water run-off.  It also provides shelter and is an important food source for many species including Clark’s nutcrackers and grizzly bears.  This new research suggests that these “ecosystem services” that whitebark pine provides may be even more greatly impacted by the climate fueled beetle attacks than we had previously anticipated.

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As the impacts of climate change are detected in more microclimates and ecosystems, examples like the warming of pine forests in British Columbia will only become more common – and their effects more dramatic.  It is time to focus our attention proactively on climate change before large ecosystems collapse.  In whitebark pine forests, resource managers should increase restoration efforts in damaged areas while continuing to pursue research to minimize beetle invasions and increase whitebark pine resistance and resilience.  From a wildlife perspective, given the complex level of uncertainty that these outbreaks will bring, we will need to be managing for robust populations of species to maximize their ability to adapt to the many unpredictable conditions they are yet to face.  More broadly, of course, reducing fossil fuel emissions and switching to clean energy sources will ultimately be needed to combat global warming and its many effects. 

(Photos © NRDC available at: and

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