Beetle Kill 2009: What part of the epidemic cycle are we in?
May 8, 2009
You probably don’t have to tell anyone who lives in Grand County that the current mountain pine beetle (MPB) epidemic is occurring at a historically unprecedented scale. This has been their reality since 2001, when it became apparent this beetle infestation was like no other. This little rice-sized pest has been working its way through most of the mature lodgepole pine the county has to offer. The MPB doesn’t care whose jurisdiction or how attached we are to our mature lodgepole pine trees.
The outbreak Grand County continues to experience was triggered by extended drought and warm winters. These conditions stressed a lodgepole pine forest that was already at a moderate to high risk for beetle infestation based on size, age, and elevation. Consequently, the beetle population exploded resulting in high levels of mortality, successful attacks in small trees, and occasionally the infestation of less preferred species such as spruce. The warm weather has encouraged them to move on to the next trees sooner. They used to fly in July and August and they now are making their new “hits” as early as June at this elevation and they are often attacking new trees above the insecticide spray line much higher on the tree then before.
So what will make the beetles stop? Potentially they will stop if they run out of mature lodgepole pine that are greater than five inches in diameter to bore, feed on and spread their blue stain tree-killing fungus. They also may stop if the county experiences unusually cold sustained temperatures of 30 degrees below zero. These temperatures in the past have been known to kill MPB larvae before they grow into adult beetles and move on to their next victim. Believe it or not, these beetle outbreaks are a part of a natural process and a way of regenerating the next forest however; humans haven’t experienced an outbreak this large.
Data from the 2008 Aerial Survey may indicate that the outbreak in Grand County is slowing compared to other counties. Approximately 27,000 new acres were impacted between 2007 and the 2008 survey for a total of 552,570 acres since this epidemic began in the county in 1996. In places where logging and hazardous fuels reduction projects have taken place, regeneration of the next forest has begun. It is also beginning beneath the standing, needle-free, dead trees. The forest that is coming in is more diverse than the homogenous stands of mature lodgepole that existed before. Aspen, spruce and fir are regenerating with lodgepole pine. We are beginning the stage of the forest renewing itself.
This doesn’t mean the outbreak is over. More trees will be attacked. The MPB may continue to do new things. Red and dead trees will dominate the hillsides. Fire danger will change across the county as the dead trees lose their needles and eventually fall down. In addition, the dead trees are no longer taking up water. Therefore, increased runoff from snowmelt is expected and may result in flooding or delay opening of seasonal roads, trails and campgrounds. No matter what happens, the Forest Service and the multitude of cooperators and partners will continue to work together to reduce the impacts from wildfire to communities and watersheds.