Climate plays a key role in determining the extent and severity of insect outbreaks and wildfires (Juday, G. P. et al 2005, Balshi, M. S.,et al 2009). During the 1990s, for example, south-central Alaska experienced the largest outbreak of spruce beetles in the world (Ryan, M. G. et al 2008, Juday, G. P. et al 2005). This outbreak occurred because rising temperatures allowed the spruce beetle to ... survive over the winter and to complete its life cycle in just one year instead of the normal two years. Healthy trees ordinarily defend themselves by pushing back against burrowing beetles with their pitch. From 1989 to 1997, however, the region experienced an extended drought, leaving the trees too stressed to fight off the infestation.
Prior to 1990, the spruce budworm was not able to reproduce in interior Alaska (Juday, G. P. et al 2005). Hotter, drier summers, however, now mean that the forests there are threatened by an outbreak of spruce budworms (Fleming, R. A., and W. J. A. Volney 1995). This trend is expected to increase in the future if summers in Alaska become hotter and drier (Juday, G. P. et al 2005). Large areas of dead trees, such as those left behind by pest infestations, are highly flammable and thus much more vulnerable to wildfire than living trees.
credit: United State Global Change Research Program, Berman, M., G. P. Juday, and R. Burnside
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