A spatiotemporal pattern analysis of potential mountain pine beetle emergence in British Columbia, Canada

Abstract

Emergence, the beginning of the mountain pine beetle life cycle and initiation of dispersal leading to colonization of new hosts, is a key beetle population process but it is also probably the least understood. Although from the management perspective information on beetle emergence is crucial in determining an appropriate timing to monitor beetle populations and mitigate outbreaks, especially at the landscape scale in a changing climate, no attempt has yet been made to map the spatiotemporal patterns of beetle emergence across the landscape. In this study, we used a novel heating cycle approach to map potential beetle emergence spatially and temporally. This study reveals that the thermal environment and timing for potential beetle emergence are spatially and temporally synchronous across the landscape. The spatial synchrony in potential beetle emergence occurs at a distance of more than 1500km across the BC landscape. The spatiotemporal patterns of potential beetle emergence vary with the defined factors (region, period, latitude, elevation, and landform type). At the provincial and regional levels, the thermal environment for potential beetle emergence is surprisingly warmer during 1977–1987 compared to 1999–2010 except for the Southeast region although the provincial climate and weather are generally warmer during 1999–2010 than during 1977–1987, suggesting a small increase in annual temperature may not be enough to significantly improve the thermal environment. A warmer thermal environment with a larger temporal window for potential beetle emergence (i.e., the potential emergence starts earlier and ends later) is associated with the Southeast region, lower latitude and elevation, and landscape topographic features of canyons and valleys. However, although the thermal environment varies with the defined factors, the timing and window of potential beetle peak emergence remain consistent among these defined factors, suggesting that beetles may take different strategies to adapt to temporally synchronized thermal windows in the regions and areas with varied thermal environments. The summarized variables of heating cycles are limited in generally predicting the beetle infestations for a specific period, especially at endemic and incipient levels. However, they may play a greater role in predicting more severely infested areas. The heating cycle approach demonstrated in this study may provide a simple complementary tool to the existing climate suitability models in assessing the impacts of climate change on beetle outbreaks, particularly for those bark beetle species whose physiological responses to temperature have not been fully studied.