The Intersection of Independent Lies: Increasing Realism in Ecological Risk Assessment

ABSTRACT

In 1966, Levins presented a philosophical discussion on making inference about populations using clusters of models. In this article we provide an overview of model inference in ecological risk assessment, discuss the benefits and trade-offs of increasing model realism, show the similarities and differences between Levins' model clusters and those used in ecological risk assessment, and present how risk assessment models can incorporate Levins' ideas of truth through independent lies. Two aspects of Levins' philosophy are directly relevant to risk assessment. First, confidence in our interpretation of risk is increased when multiple risk assessments yield similar qualitative results. Second, model clusters should be evaluated to determine if they maximize precision, generality, or realism or a mix of the three. In the later case, the evaluation of each model will differ depending on whether it is more general, precise, or realistic relative to the other models used. We conclude that risk assessments can be strengthened using Levins' idea, but that Levins' caution that model outcome should not be mistaken for truth is still applicable.

Keywords:

• risk assessment
• model clusters
• trade-offs
• model uncertainty
• realism
• precision
• generality.

ACKNOWLEDGMENTS

We thank the participants of the Intersection of Independent Lies Conference (January 2005, Andrews Experimental Forest, OR) for stimulating discussion, especially Jennifer Orme-Zavaleta and Phil Rossignol, conference organizers. Jason Grear and two anonymous reviewers provided constructive comments on this manuscript. The information in this document has been funded by the U.S. Environmental Protection Agency.

This article has been subjected to review by the National Health and Environmental Effects Research Laboratory's Western Ecology Division and approved for publication. Approval does not signify that the contents reflect the views of the Agency, nor does mention of trade-names or commercial products constitute endorsement or recommendation for use. This article is a work of the US Government and is not copyrighted.