Lines of Evidence in Wildlife Risk Assessments

Abstract

Methods for assessing risk to wildlife from exposure to environmental contaminants remain highly uncertain as empirical data required for accurate estimates of exposure or determination of toxicity thresholds are lacking. Some practitioners have advocated an ecological approach (i.e., “top down”) to wildlife assessments to account directly for the uncertainties inherent in aggregating direct toxicological effects to individuals when estimating population risk (i.e., “bottom up” techniques). This paper suggests a methodology for conducting wildlife risk assessments that incorporates both the “bottom up” and “top down” techniques by taking into account multiple lines of evidence that are gathered by proceeding through a tiered approach including: 1) concentration of chemicals in relation to levels reported to be harmful; 2) bioassays or toxicity studies to define dose-response relationships; and 3) field studies of population or community responses. A step-wise process progressing through these three tiers is a cost-effective method for developing the necessary information. This method is analogous to standard epidemiological approaches. Incorporation of continued monitoring and directed field studies into risk management is suggested as a means to move forward with environmental management decisions in the face of the significant uncertainties that will continue to be associated with wildlife risk assessments.

Keywords:

• weight-of-evidence
• risk assessment tiers
• sediment quality triad
• risk management.