The value of nonindigenous species risk assessment in international trade

Managing the introduction of nonindigenous species is becoming a major goal of policy-makers at regional, national and international scales. Here we investigate, at the national level, the ideal design and expected net benefits of a risk assessment program for evaluating the desirability of nonindigenous species imports. We show how to enhance the statistical rigor of such a system by correcting a common non-random sampling problem encountered in the data. This correction enables model output to be interpreted in an economically relevant way and facilitates a theoretically rigorous characterization of the balance between trade and nonindigenous species establishment risk. Using reptiles and amphibians imported to the U.S. as a case study, we characterize economic outcomes over a range of cases and demonstrate substantial expected returns to such a screening program, relative to the current effectively open-door policy. Our results are informative for the current debate in the U.S. about whether to require federal agencies to apply risk assessment before allowing a species for import. The framework presented decomposes a complex argument about risk management into component economic and statistical parts, allowing for debate and improved understanding over each element to inform the overall program in a transparent fashion.