Mountain pine beetle (Dendroctonus ponderosae, MPB) is a native insect in the pine forests of western North America. In recent decades, MPB has experienced a large-scale range expansion that has caused massive tree mortality. Climatic variations have been suggested as a driving factor in creating a favorable environment for MPB through milder winters, warmer growing seasons and increased drought events. However, it is still unclear if MPB has migrated into a new climate space with significantly different climatic conditions from the past. For this project, we utilize spatially interpolated Climate Research Unit (CRU) data to plot the climate space of MPB with twelve critical climatic variables identified from literature, such as minimum winter temperature, maximum August temperature, and growing season precipitation, and provide specific measures describing the current geographical space of MPB across North America. We apply topographically adjusted bilinear interpolation on the CRU 10 min 1961-1990 long-term means and the CRU 0.5-degree 1901-2014 monthly time series to create climate data on a 10km grid. The dynamics of climate space in different host species and all core hosts during 2000 – 2014 are examined to understand the climate constraints.
Climate space is constructed from the plot of pairs of climatic variables, and climatic conditions are summarized from statistical indicators. MPB has emerged in a drier and warmer climate space in North America in recent years; however, it may have also adapted to colder winter temperatures. Looking forward, there is a potential for MPB expanding its climate space into the jack pine component of the boreal forest, based on the shared area of climate space between beetle presence and absence in host species. We have found MPB-adapted climate conditions have been shifted from long-term means and identified climatic constraints, for instance, there is an absence of beetles under the climate conditions of: growing season precipitation higher than 800 mm, mean maximum August temperature lower than 10 °C, and minimum winter temperature lower than -30 °C. These preliminary results suggest that the insect can adapt to climate change by modifying its climate space, although there are certain thresholds in the critical climatic variables, or boundaries in the climate space. The study can provide specifications for climate suitability modeling at a large scale in future research, such as identifying the most significant climatic variables and predicting beetle presence from spatial simulation.