Category: Ecological Research
Title: Working Paper 31: Climate Change Impacts on Bark Beetle Outbreaks and the Impact of Outbreaks on Subsequent Fires.
Author: Gaylord, M.L.
Subject: Climate Change, Bark beetle, Fire
Abstract: The Insect Bark beetles are small insects that can have profound impacts on forests. While some species of bark beetles primarily attack trees that are recently dead or dying, others attack live, vigorous trees and can cause tree mortality across extensive areas. The Southwest is home to multiple species of bark beetles (Gaylord et al. 2006, Williams et al. 2008). In southwestern ponderosa pine forests the most notable bark beetle species belong to the genus Ips or Dendroctonus. Ecological Role and Impacts Bark beetles and fire share similar roles in southwestern ponderosa pine forests. Similar to fire, bark beetles are natural disturbance agents and help with nutrient redistribution. Tree mortality from bark beetles helps with snag formation, providing vital habitat for cavity nesting birds and bats, among other wildlife. Bark beetles are a food source for other insects and birds. At low bark beetle populations, tree mortality ranges from individual trees to small groups of trees leading to gap formation and increasing forest heterogeneity. Epidemics, or outbreaks, are also part of the natural cycle. In some ecosystems, such as mountain pine beetle in lodgepole pine, the forests are homogenized after these outbreaks, helping to perpetuate lodgepole pine stands (Brown 1975). Historically, epidemics would subside due to excessively cold temperatures or because suitable host material (tree species or preferred diameter range) becomes depleted. Current bark beetle outbreaks in some forest systems are considered unprecedented (Raffa et al. 2008, Bentz et al. 2009). Recent outbreaks appear to be driven by warmer/drier climate, an abundance of overstocked and homogeneous stands caused by past management decisions, or a combination of these and other factors (Raffa et al. 2008, Bentz et al. 2010, Fettig et al. 2013). In essence, large-scale outbreaks are a result of many of the same factors driving catastrophic fires and, consequently, both disturbance agents are having impacts on ecosystems that are often outside of their historic range of variability.
Type: Fact Sheet
Source: ERI - Working Papers
Publisher: Ecological Restoration Institute