The Signature of Endemic Populations in the Spread of Mountain Pine Beetle Outbreaks

Abstract

The mountain pine beetle (MPB) is among the most destructive eruptive forest pests in North America. A recent increase in the frequency and severity of outbreaks, combined with an eastward range expansion towards untouched boreal pine forests, has spurred a great interest by government, industry and academia into the population ecology of this tree-killing bark beetle. Modern approaches to studying the spread of the MPB often involve the analysis of large-scale, high-resolution datasets on landscape-level damage to pine forests. This creates a need for new modelling tools to handle the unique challenges associated with large sample sizes and spatial effects. In two companion papers (Koch et al. in Environ Ecol Stat.

Eruptive insect outbreaks from endemic populations under climate change

“…Endemic populations are frequently considered to be stands with less than 5 attacked trees per ha (Boone et al 2011), with studies finding between 3 – 6 infested trees per ha in mature lodgepole pine stands (Safranyik and Wilson 2006) and 1 – 2 attacked trees per ha in the lodgepole x jack hybrid zone in Alberta (Bleiker et al 2014). Another study fitting a model in British Columbia found 7 – 14 attacking beetles per ha (Koch et al 2021), which for φ L = 5 roughly corresponds to 1 – 2 infested trees per ha. These estimates from available data correspond to the low end of our model predictions for the endemic equilibria, and specifically are attained for a small fraction of low vigor trees of around 1%.…”

Special Collection: Celebrating J.D. Murray’s Contributions to Mathematical Biology

“…Much of Murray's pioneering work features multi-stable systems, where nonlinear dynamics can drive multiple possible outcomes. Koch et al (2021) analyse a classical multi-stable system, mountain pine beetle populations, which can jump between endemic and outbreak states. However, this work develops a new perspective on such systems by incorporating spatial autocorrelation in dispersal dynamics for the beetles.…”