INSECT POPULATION DISTRIBUTION AND CLIMATE CHANGE

Latitudinal Shifts in Spruce Budworm (Lepidoptera: Tortricidae) Outbreaks and Spruce-Fir Forest Distributions with Climate Change

Williams, D.W. and Liebhold, A.M. (1997): Latitudinal Shifts in Spruce Budworm (Lepidoptera: Tortricidae) Outbreaks and Spruce-Fir Forest Distributions with Climate Change. Acta Phytopathologica et Entomologica Hungarica 32, 203-215.

Abstract:

Changes in global temperatures over the next century resulting from the greenhouse effect may have profound effects on the distribution and abundance of insect populations. One general hypothesis is the poleward shift of species distributions. We investigated potential range shifts for the spruce budworm, Choristoneura fumiferana, in the Northeastern and North central United States using maps of historical outbreak areas, climatic variables, and the distribution of spruce-fir forests in a geographic information system. We developed canonical discriminant function models of the occurrence of defoliation and the distribution of spruce-fir forests as functions of climatic variables. Using these models, we developed scenarios for defoliation and forest type changes resulting from temperature increases of 2º, 4º, and 6º C. In general, predicted areas of defoliation and of the forests decreased in size with increases in temperature. As temperatures increased, distributions of defoliation and spruce-fir forests exhibited a general pattern of thinning and disappearance at their southern margins, suggesting a northward shift of both budworm populations and spruce-fir forests.

Results are available for viewing to the left. Note that defoliation distributions were available only for Minnesota and Maine.