Using Regression Analysis and Machine Learning to Investigate the Connection Between Mountain Pine Beetle (Dendroctonus ponderosae) Outbreaks and Human-Induced Climate Change

The impacts of both natural and human-induced climate change are evident across the pine (Pinus) dominated forests of the Northern Rocky Mountains, USA. Paleoecological records have been used to investigate climate driven vegetation change and the complexities of fire disturbance in these forests over the Holocene, providing important information to the development of forest management plans and fire suppression protocols. 

Mountain pine beetle (Dendroctonus ponderosae) (MPB) outbreaks have also influenced ecosystem change in the Northern Rocky Mountains. However, little is known about the occurrence of MPB outbreaks beyond the historic time period (past 200 years). Without direct evidence (fossil beetle remains) to identify MPB outbreaks in paleoecological records, it has been challenging to identify the timing and frequency of outbreaks over a longer time period (Holocene) and to demonstrate how unusual the patterns of the past 200 years are. The increase in MPB outbreaks in the historic time period has been attributed to increasing temperatures affecting the reproductive cycle of the beetles and the weakening of the defense mechanisms in pine species. Understanding the frequency of MPB outbreaks and forest response over the Holocene is helping land managers better plan for the future management strategies of these iconic landscapes. 

This project used both traditional paleoecological time series analysis and quantitative analysis (regression analysis and machine learning) to investigate the frequency and timing of MPB outbreaks over the Holocene and identify patterns related to climate change. The data presented are from a series of sites across an elevational and latitudinal gradient in the Northern Rocky Mountains, USA and includes periods of high resolution (every cm) paleoecological proxy data. Initial findings indicate a positive relationship between MPB outbreaks and pine (Pinus) dominance on the landscape and more frequent MPB outbreaks during the historic time period than during any other time throughout the Holocene.