INFLUENCES OF CLIMATIC-CHANGE ON SOME ECOLOGICAL PROCESSES OF AN INSECT OUTBREAK SYSTEM IN CANADA BOREAL FORESTS AND THE IMPLICATIONS FOR BIODIVERSITY

Insect outbreaks are a major disturbance factor in Canadian forests. I f global warming occurs, the disturbance patterns caused by insects ma y change substantially, especially for those insects whose distributio ns depend largely on climate. In addition, the likelihood of wildfire often increases after insect attack, so the unpredictability of future insect disturbance patterns adds to the general uncertainty of fire r egimes. The rates of processes fundamental to energy, nutrient, and bi ogeochemical cycling are also affected by insect disturbance, and thro ugh these effects, potential changes in disturbance patterns indirectl y influence biodiversity. A process-level perspective is advanced to d escribe how the major insect outbreak system in Canadian forests, that of the spruce budworm (Choristoneura fumiferana Clem. [Lepidoptera: T ortricidae]), might react to global warming. The resulting scenarios h ighlight the possible importance of natural selection, extreme weather , phenological relationships, complex feedbacks, historical conditions , and threshold behavior. That global warming already seems to be affe cting the lifecycles of some insects points to the timeliness of this discussion. Some implications of this process-level perspective for ma naging the effects of global warming on biodiversity are discussed. Th e value of process-level understanding and high-resolution, long-term monitoring in attacking such problems is emphasized. It is argued that a species-level, preservationist approach may have unwanted side-effe cts, be cost-ineffective, and ecologically unsustainable.