Canadian Forest Service Publications
Towards reliable mapping of biosecurity risk: incorporating uncertainty and decision-makers’ risk aversion. 2015. Yemshanov, Denys; Koch, Frank H.; Ducey, Mark; Haack, Robert A.Wallingford, UK: Biosecurity Surveillance Quantitative Approaches CABI Publishing. 12:217-237 21 p.
Issued by: Great Lakes Forestry Centre
Catalog ID: 36285
Availability: PDF (download)
Pest risk maps are an important source of decision support when devising strategies to minimize introductions of invasive organisms and mitigate their impacts. When possible management responses to an invader include costly or socially sensitive activities, decision makers tend to follow a more certain (i.e. risk-averse) course of action. We present a new mapping technique that assesses pest invasion risk from the perspective of a risk-averse decision maker. We demonstrate the approach by evaluating the likelihood that an invasive forest pest will be transported to one of the continental US states or Canadian provinces in infested fi rewood that may be carried by visitors to US federal campgrounds. We test the impact of the risk aversion assumption using distributions of plausible pest arrival scenarios generated with a geographically explicit model developed from data documenting camper travel across the study area. Next, we prioritize regions of high and low pest arrival risk via application of two stochastic ordering techniques that employ,respectively, fi rst- and second-degree stochastic dominance rules, the latter of which incorporates the notion of risk aversion. We then identify regions in the study area where incorporating risk aversion changes a region’s pest risk value considerably. While both methods identifi ed similar areas of highest and lowest risk, they diff ered in how they demarcated moderaterisk areas. Each method provides a tractable way to incorporate decision-making preferences into fi nal risk estimates, and thus helps to better align these estimates with particular decision-making scenarios about an organism of concern. Overall, in - corporation of risk aversion helps to refi ne the set of locations that could be confi dently targeted for costly inspections and outreach activities.
Plain Language Summary
Risk assessments and maps can help forest managers develop strategies to reduce the number of introductions of new invasive organisms. Knowledge about an invasive organism’s behavior in its new environment is rarely complete, so assessments of potential risks and impacts include a lot of uncertainty. Consequently, a decision made on the basis of such an assessment depends not only on the estimates of pest invasion risk and potential impacts, but also on how the decision-makers perceive the uncertainty in these estimates. When possible management responses to an invasive threat include costly, irreversible or socially sensitive activities, decision makers tend to exhibit risk-averse or risk-neutral behavior. In this paper we present a set of new practical risk assessment and geographical mapping techniques that help incorporate uncertainty and the decision-maker’s risk perceptions into risk assessment products. We adapt ordering techniques that have been commonly used in the financial world to incorporate uncertainty and decision-making perceptions directly into estimates of invasion risk. We illustrate the approach with case studies that assess risks of ecological invasion in a geographic domain from the perspective of a risk-averse decision-maker. Overall, the new approach offers a better strategy for dealing with typical uncertainties in assessments of biosecurity risks and provides a manageable way to incorporate decision-making preferences into final risk estimates.