• Australian Weed Risk Assessment;
  • biological invasions;
  • consequence;
  • impact;
  • invasiveness;
  • invertebrates;
  • likelihood;
  • plants;
  • risk assessment;
  • vertebrates;
  • WRA



An increasingly important component of invasive species management involves the formal assessment of risks associated with particular species becoming invasive and causing impact. We evaluated recent developments in risk assessment (RA) for alien species, with special emphasis on species-based pre-border assessments for intentional introductions. Our aim was to identify important advances and key challenges.




A literature review was done to determine which approaches have been developed and fine-tuned over the last two decades, which of these have worked best and which are most widely used. We identified priorities for improving our ability to assess risks.


The review is divided into sections on various types and foci of RAs: invasion stage, taxon, ecosystem, assessment method and impact type. RAs for plants are the most advanced, with the Australian Weed Risk Assessment (A-WRA) being the most widely applied and tested protocol. Based on the history of the A-WRA, we highlight advances that have been made in assessing risk of alien species for pre-border control and identify remaining challenges.

Main conclusions

Currently available RAs have proven to be cost-effective, but there is room for substantial improvement. Further work is needed to separate likelihood and consequence more explicitly, and provide better and more objective means for assessing risks of impact. Types and levels of uncertainty need to be more effectively incorporated. Advanced RA protocols are needed for taxa other than plants and vertebrates. The latest insights from research in invasion ecology need to be incorporated, and advances in other fields must also be taken into account.