Promise and challenges of risk assessment as an approach for preventing the arrival of harmful alien species

Background: Harmful alien species impose a growing environmental, economic and human well-being burden around the globe. A promising way to reduce the arrival of new species that may become harmful is to utilise pre-border risk assessment (RA) tools that relate the traits of introduced species to whether those species have become established and harmful. These tools can be applied to species proposed for intentional introduction so that informed decisions can be made about whether each species poses an acceptable risk and should be allowed for import. Objectives: A range of approaches to RA tool development have emerged, each relying on different assumptions about the relationships between traits and species impacts, and each requiring different levels and types of data. We set out to compare the qualities of each approach and make recommendations for their application in South Africa, a high biodiversity developing country that already has many invasive species. Method: We reviewed five approaches to pre-border RA and assessed the benefits and drawbacks of each. We focused on how pre-border RA could be applied in South Africa. Results: Recent legislation presents a framework for RA to evaluate species introductions to South Africa, but we find that this framework assumes an approach to RA that is relatively slow and costly and that does not leverage recent advances in RA tool development. Conclusion: There is potential for proven RA approaches to be applied in South Africa that would be less costly and that could more rapidly assess the suite of species currently being introduced.