Ecological and Bioeconomic Risk Assessment for Invasive Species

Human transport of live organisms presents a policy challenge for globalization:activities that move organisms benefit society, but some nonindigenous species become invasive and cause harm. Although ecological predictions of future impacts from invasive species are rarely used in management, they have great potential to guide risk reduction efforts. Here, I construct risk assessments for predicting the identity and location of future invaders. Additionally, I calculate the benefits from implementing risk reduction programs based on ecological predictions. I begin by assessing the risk posed by introductions of freshwater species and earthworms for the pet, nursery, bait, biological supplies and live food trades in the Laurentian Great Lakes (LGL) region. My results show that these trades present large risks of both introducing new invasive species and of spreading established invaders. To address the risk of new invasions, I have constructed a risk assessment model that relates mollusc natural history to risk of becoming invasive in either the LGL or the continental U.S. This model accurately predicts the likely harm from molluscs that may be introduced in the future. Ecological predictions can also guide efforts to reduce the risks from established invaders, and I have used historical data from the rusty crayfish (Orconectes rusticus) invasion of Northern Wisconsin (USA) to produce a model for predicting the lakes most at risk from invasion. Testing this model on an independent dataset demonstrated that it has high accuracy. Although ecological predictions of the risk from invasive species are becoming more accurate, these predictions are rarely used in management, partly because prevention efforts are expensive and many believe that their costs will outweigh their benefits. I have explicitly tested the bioeconomic outcomes from applying ecological predictions of future invasions, and show that currently available risk assessments are sufficiently accurate that the economic value gained from fewer invasions is greater than the cost of prevention efforts. This is true for both preventing new invaders, and for preventing the spread of established invasive species. Thus, there is strong environmental and economic justification for ecology to play a greater role in efforts to reduce future impacts from invasive species.