Stratification of fuels that may burn in forest fires (R. Keane 2016)

Natural disturbances, such as fire, insect infestations, diseases, and extreme weather, are integral to most North American ecosystems.  Scientists have long studied the impacts of natural disturbances on the composition and function of forest ecosystems.  However, the scale of the current bark beetle infestation in the northern Rocky Mountains far exceeds anything observed in the recent historical record.  As such, scientists are trying to understand how hundreds of millions of standing – and eventually fallen – dead trees will impact ecosystems.

Fallen trees in a beetle-killed lodgepole pine forest in Montana (photo by P. Kolb)

Some have feared that extensive stands of dead trees will lead to more frequent and catastrophic wildfires.  Recent studies have largely debunked that fear, finding that climatic conditions, especially drought, better predict the occurrence of wildfire. Though scientists agree that climate drives wildfire occurrence in live or dead forests, questions remain on wildfire dynamics as beetle-killed trees move from the canopy, to suspended surface fuels and eventually to the forest floor. One thing that is certain, is that fighting fires in beetle-killed forests is more difficult and hazardous for firefighters. Already fallen trees form a maze of obstacles for firefighters and standing dead trees are more likely to fall. In some beetle-affected stands, salvage logging of killed trees may be used in restoration efforts and to reduce hazards while supporting local wood products industries.  Scientists are currently studying how different types of salvage logging may affect the quantity and types of forest fuels, as well as the interacting microclimatic effects of removing trees, and the overall impact on wildfires.