These aspects of math are exactly what Professor Frithjof Lutscher and postdoctoral fellow Sébastien Portalier have found themselves doing in collaboration with the Healthy Forest Partnership (HFP). The HFP is a research partnership between Canadian Forest Service (a sector of Natural Resources Canada) and the University of New Brunswick—to control spruce budworm populations. The issue that Dr. Portalier and Prof. Lutscher are tackling is a small but nasty insect pest found in Canada’s forests, the spruce budworm. When they occur in large numbers, the spruce budworm can be highly destructive and have severe impact on host trees, such as balsam fir, with significant consequences for forest structure and forest industry. Such large numbers occur roughly every 30 years, for example right now in Quebec and New Brunswick. When the spruce budworm emerges from winter diapause in the spring, it requires fresh foliage to feed on. Hence, insect emergence and tree budburst must be carefully synchronized. Both of these events are based on climate conditions, which are changing at different rates in different locations.
Prof. Lutscher’s research combines climate predictions with models to determine how emergence and budburst dates will change according to temperature regimes, and to predict the effects of climate change on synchrony in different parts of the country. The goal is to create a risk map that predicts, for any given year, which parts of Canada’s forests are most susceptible to defoliation from spruce budworm. In the future, the researchers hope to integrate the model for synchrony within a year into a larger model for population dynamics between years, so that they can predict potential insect outbreak scenarios and use computer simulations to find optimal management strategies that help minimize large tree mortality.
Prof. Lutscher’s mathematical models can help focus resources to manage the insect, such as spraying insecticides in areas where the risk is highest, and thereby make risk mitigation programs more cost-effective and efficient. The partnership benefits his research program in two ways: (i) it provides him with access to data on climate, insect and tree emergence, survival and mortality, and (ii) it helps him connect two previously separate research fields: phenology and population dynamics. Phenology studies how individual organisms develop through their life cycle, in this case with respect to climatic conditions, whereas population dynamics studies how the entire population grows or declines over generations. The spruce budworm – balsam fir system offers an exciting opportunity to link these two fields and obtain new insights that help manage Canada’s forests sustainably.
