1 Application of Risk Assessment and Decision Analysis to Aquatic Nuisance Species

PURPOSE: This technical note describes a structured framework for conducting risk assessments for aquatic nuisance species (ANS). The technical note also describes when and how decision analy-sis tools can be used in such assessments for ANS. This framework and methodology will enable risk managers to systematically evaluate and compare alternatives and actions supporting ANS risk management and thus credibly prioritize resources. BACKGROUND: Risk assessment is a globally accepted tool for assessing the potential harm posed by chemical contaminants in the environment (Andersen et al. 2004a). Recently, work has begun that combines the benefits of risk assessment with the structure provided by decision analysis to bridge the gap between the detailed, quantitative output of risk assessments and simulation models with values-based and localized risk management requirements (Kiker et al. 2005; Linkov et al. 2005). An approach using the traditional ecological risk assessment (ERA) framework (USEPA 1997, 1998) combined with decision analysis tools has appeal for assessing ANS risks. While the methodology for contaminant risk assessment is well-known and universally applied, the elements of a toxicologically based risk assessment paradigm will need to be adapted to cases where the causa-tive agent for a perceived risk to the environment is an organism rather than a chemical. To effec-tively manage ANS risks, a systematic risk assessment framework that includes structured decision analysis can help organize and analyze pertinent data, state assumptions, address uncertainties in estimating the probability of an undesired event, and integrate these outputs with stakeholder values. INTRODUCTION: The establishment and spread of nonindigenous (non-native) species introduced into the United States is a significant and growing national problem. Problems are manifested via lost agricultural productivity, increased health problems, environmental degradation to the point of extinction of native species and expensive prevention and eradication efforts (Andersen et al. 2004a