Mapping ecological risks with a portfolio-based technique: incorporating uncertainty and decision-making preferences
Article first published online: 6 MAY 2013
© Her Majesty the Queen in Right of Canada 2013. Reproduced with the permission of the Minister of Natural Resources Canada.
Diversity and Distributions
Special Issue: Risks, Decisions, and Biological Conservation
Volume 19, Issue 5-6, pages 567–579, May & June 2013
How to Cite
Yemshanov, D., Koch, F. H., Ducey, M., Koehler, K. (2013), Mapping ecological risks with a portfolio-based technique: incorporating uncertainty and decision-making preferences. Diversity and Distributions, 19: 567–579. doi: 10.1111/ddi.12061
- Issue published online: 6 MAY 2013
- Article first published online: 6 MAY 2013
- Agriculture and Food Research Initiative Competitive. Grant Number: 2010-85605-20584
- National Institute of Food and Agriculture
- Epistemic uncertainty;
- human-assisted spread;
- mean-variance frontier;
- road network;
- stochastic dominance
Geographic mapping of risks is a useful analytical step in ecological risk assessments and in particular, in analyses aimed to estimate risks associated with introductions of invasive organisms. In this paper, we approach invasive species risk mapping as a portfolio allocation problem and apply techniques from decision theory to build an invasion risk map that combines risk and uncertainty in a single map product.
We divide the study area into a set of spatial domains and treat each domain as an individual ‘portfolio’ with a unique distribution of the expected impacts of invasion. The risk of invasion is then mapped by finding nested ‘efficient’ portfolio sets that identify the geographic areas exhibiting the worst combinations of the estimated risk of invasion and the uncertainty in that estimate. For Canadian municipalities, we apply the approach to quantify the risk that a given location will receive invasive forest pests with commercial freight transported via the North American road network. We compare risk allocation techniques that employ the concepts of nested mean-variance (M-V) frontiers and second-degree stochastic dominance.
While both methods based on M-V and the stochastic dominance principles identified similar areas of highest risk, they differed in how they demarcated moderate-risk areas. Furthermore, they address uncertainty in different ways, treating it as a risk premium (in the case of nested M-V frontiers) or producing risk-averse delineations (in the case of stochastic dominance).
The portfolio-based approach offers a viable strategy for dealing with the typically wide variability in risk estimates caused by a lack of knowledge about a new invader. The methodology also provides a tractable way of incorporating decision-making preferences into the final risk estimates and thus better aligns risk assessments with particular decision-making scenarios about the organism of concern.