The emerging significance of bark beetle outbreaks in the Rocky Mountains

Background/Question/Methods

Bark beetles are significant disturbance agents of forests in the Rocky Mountains.  In 2002, epidemics that affected substantial areas had been documented.  Fundamentals of drivers of these events were understood, including the role of climate.  Since 2002, however, several significant developments have occurred related to these disturbances.  In this presentation, we will describe these developments and speculate on future patterns and impacts of epidemics.

Results/Conclusions

We will discuss three developments.  First, major epidemics that were only just building in the early 2000s continued to expand, resulting in the greatest amount of area of tree mortality caused by biotic disturbances in recorded history.  Current understanding suggests that beetle epidemics are comparable to wildfire in terms of area of impacts.  Second, modifications to beetle outbreak characteristics have occurred in recent years.  We discuss three situations: intensified outbreaks beyond the historic range of variability, but within the historic distribution; shift of ecological roles and impacts in habitats that historically did not support outbreak populations; and invasion of previously unoccupied habitats.  Finally, our understanding of the impacts of these disturbances on wildfire, carbon sequestration, and hydrology have progressed rapidly in recent years associated with large areas of tree mortality and concern by resource managers and the public.  We will discuss management and restoration options and prospects for future forest renewal under a scenario of rapid climate change.