Theoretical framework for assessment of risks posed to Canadian forests by invasive insect species

• Climate change is causing range expansions and increases in outbreak frequency and severity of forest insect.
• Forest managers need information about the potential impacts of forest pests under this new scenario.
• Current knowledge is scarce and our capacity to react is limited.
• We propose a general framework to evaluate the risk and impacts of forest insects on new habitats.
• We provide an example to illustrate the application and scope of the proposed framework.

Climate warming is causing increases in severity of outbreaks and range expansion in a number of insect pests and diseases. Under these conditions, forest managers should choose the best silvicultural practices to optimize production of timber and ecosystem services, while reducing pest damage to tolerable levels. However, information on the short and long term impacts of key pests, such as mountain pine beetle (MPB) (Dendroctonus ponderosae Hopkins), especially when they occur outside their historical geographical range, is scarce and our ability to predict, pre-empt and react to problems is, therefore, limited. Here we propose a general framework to evaluate the risk and impacts of important forest insects in new habitats, and to identify information gaps when conducting risk assessments. The framework consists of four main steps. The first step of risk assessment under potential range expansion is to identify the factors that promote pest spread and colonization of new environments (hazard). A second step is to determine the area at risk and the potential economic impacts (exposure). The third step is to establish if the forest in the new habitat is susceptible to colonization and pest range expansion (vulnerability). The fourth and final step is to determine the options for risk communication and mitigation. We also illustrate the scope and application of this response framework to decision makers, using, as an example, the potential spread of MPB from its native habitats in BC and Alberta into the boreal forests of Canada, especially with regard to the forests of Quebec.