Characterising uncertainty in risk assessments for biological control: using case studies from New Zealand to inform future research

Areas of uncertainty in the assessment of risks and benefits in applications for new biological control agents submitted to the regulator for proposed introduction into New Zealand were identified. This was done with the aim of informing future research priorities which might be able to address and reduce these areas of uncertainty to assist decision-making in the future. A sample of 20 applications received by the Environmental Protection Authority (EPA) between 2009 and 2019 were selected, with examples from weed and insect targets. Expressions of uncertainty were identified by applicants as well as the EPA staff assessment report of the application, and the final decision document prepared by the Authority’s committee. The most common risk uncertainties expressed were potential direct non-target effects (85%), cultural risks (75%), and whether there were existing (and possibly effective) natural enemies of the target already present in the new range (70%). Food web indirect effects and adequacy of host range testing were also mentioned in more than half of the case study applications and associated documents. For uncertainty relating to benefits, 75% of case studies mentioned uncertainty about the efficacy of the proposed biological control agent, or if the agent would be successful by establishing and spreading (60%). For several of the case studies questions were raised about the method of cost: benefit analyses that had been presented in the application. Recommendations for future research are presented.