Methods to Assess Landscape-Scale Risk of Bark Beetle Infestation to Support Forest Management Decisions

The objective is to provide practitioners with suggestions on how to select appropriate methods for risk assessment of bark beetle infestations at the landscape scale in order to support their particular management decisions and to motivate researchers to refine novel risk assessment methods. Methods developed to assist and inform management decisions for risk assessment of bark beetle infestations at the landscape scale have been diverse, ranging from simple empirical correlations to complex systems models. These approaches have examined different bark beetle species, forest types and systems, and management questions, and they differ in spatial and temporal precision, the types of processes included, and the form of output. Bark beetle risk assessment methods, however, share a common theme: they aim to quantify expected levels of attack and loss due to beetles. By focusing on this commonality, presented here is a gradient in which methods can be classified and ranked, ranging from more structural, pattern-oriented methods to more functional, process-oriented methods. The objective is to describe a framework for comparing methods in terms of how risk is represented and in terms of the complexity of application. To illustrate how diverse methods can be cast within a common frame of reference, brief examples are provided of four types of methods that we have used in British Columbia, Canada, to examine landscape-scale risk of mountain pine beetle attack in lodgepole pine forests. Then provided is some guidance on how to select an appropriate method for a given system and set of questions. The most appropriate method is the simplest one that can address the questions, minimize uncertainty, and inform the decision process in the required timeframe. It is important that researchers and practitioners can view bark beetle risk-assessment methods as a toolkit and to select appropriate tools for a given task, as no single method is best for all situations.