Spruce Budworm and the Forest

Abstract

The spruce budworm is a defoliator of boreal forests in North America and can cause major impacts to spruce and balsam fir, which are important tree species in the logging industry. While most years the spruce budworm density is low and little harm comes to these trees, periodically throughout history large outbreaks of the spruce budworms occurred. These outbreaks caused major losses to the trees and to economic industries tied to the trees. As a result, the spruce budworm is one of the most well-studied—empirically and theoretically—ecological systems. Here, we introduce and explore the spruce budworm system. In our examination of the spruce budworm, we begin with a simple model describing the budworm dynamics alone. Our analysis and simulation of even the simple model demonstrates the complicated dynamics it can produce, as a function of a parameter that depends on the health and size of the forest. We then expand the system to include the forest as a variable itself and include feedbacks with the spruce budworm. We extend our analyses and simulation for this more complete system.