Canadian Forest Service Publications
Forecasting the response to climate change of the major natural biotic disturbance regime in Ontario's forests: the spruce budworm. 2008. Candau, J.N.; Fleming, R.A. Climate Change Research Report CCRR-13. 23p.
Issued by: Great Lakes Forestry Centre
Catalog ID: 34352
Availability: PDF (request by e-mail)
Predicting the effect of climate change on insect populations is needed to estimate the costs and benefits of protecting forests from potential damage. Outbreaks of forest insects and diseases in Canada cause losses of 80-110 million m3 of timber per year, or roughly one billion m3 over a 10-year period. These exceed one-half of harvest rates (which are about 160-180 million m3/yr). Many of the processes that lead to stand-replacing outbreaks of insect species depend on climate either directly, through reduced survival following extreme weather events, or indirectly through other effects on host trees. Insect pests are thus a major, but consistently overlooked, forest ecosystem component that have manifold consequences to the structure and function of future forests. This study focused on the spruce budworm because it is the dominant abiotic disturbance in Ontario forests. Global climate change may substantially change the frequency and intensity of pest outbreaks, particularly at the margins of host ranges. The consequent shunting of carbon back to the atmosphere rather than to sequestration in forests as biomass may also influence global warming. This study contributed to better estimation of climate change effects on insect outbreaks and the consequent impacts on carbon sequestration by:validating and analyzing the GIS data of Ontario's forest health survey records for spruce budworm defoliation and synthesizing the results; analyzing and developing models describing climate - insect outbreak relationships for spruce budworm in Ontario; and developing and applying a method for forecasting how climate change is likely to affect the severity and spatial locations of future insect outbreaks. In the first stage, this method was applied to survey records of spruce budworm defoliation in Ontario in combination with the corresponding historical climate records. The frequency with which a site was defoliated was found to be related to tree species composition and climate (i.e., temperature and precipitation at certain times of the year). In the final stage, predictions of future climate were incorporated for forecasting how spruce budworm defoliation in Ontario might be affected by future climate change. In the resulting forecasts, the total area over which defoliation occurred increased because the area expanded northward but changed little in the south. In addition, the most frequent defoliation seemed to occur north of present locations.