Species-based risk assessments for alien species under the spotlight

Management of invasive species starts at national borders, or, preferably, beforehand. Risk assessment should ideally be applied to organisms or cargo prior to importation (i.e. when an application for importation is made), but may also be applied at border posts or other ports of entry. Risk assessment allows decision makers, such as customs officials, to make informed decisions on whether to allow importation of a species or variety that is not yet present in the country or region. It also serves to identify mitigatory measures that may need to be implemented if a species is allowed to be imported. The use of currently available systems has been proven to save huge costs that could accrue from damage caused by invasive species.

Acacia adoxa var. adoxa

Acacia adoxa var. adoxa is one of 626 Australian Acacia species not yet recorded outside its native range. We therefore do not know whether the species would become invasive if introduced. This attractive plant may well capture the attention of horticulturalists in the future. Formal risk assessment tools (such as the Australian Weed Risk Assessment) provide a framework for the objective evaluation of risks.
(Photo: D.J. Murphy).

The process of risk assessment involves assessing the risk of a particular type of organism establishing viable populations, becoming invasive and having negative impacts. Most successful methods, such as the widely used Australian Weed Risk Assessment (A-WRA), rely on scoring systems that need to be calibrated for use in a new area, such as a country or a particular ecosystem. Cut-off levels for accepting or rejecting species need to be determined, tested and adjusted. Also, risk assessments for alien species usually do not take into account general theories of risk, which separate the likelihood (in this case of establishment and invasion) from the consequences (negative effects).

The variety of risk assessment tools used for pre-border evaluation is quite extensive and different tools have focussed on different aspects or taxa. C·I·B post-doc Sabrina Kumschick and C·I·B Director Dave Richardson reviewed the use of such tools in assessing risks associated with alien vertebrates, invertebrates and plants. Their aims were to determine which schemes have worked best and are most widely used, and to make recommendations for improving our ability to assess the risk of alien species becoming invasive and causing damage.

They found that risk assessments tools for plants are the most advanced, with the Australian Weed Risk Assessment (A-WRA) being the most widely applied and tested protocol. The A-WRA (developed for plants in Australia and New Zealand) has been adapted for use in many other countries and regions (e.g. Japan, Czech Republic and Hawaii), and for other taxa, including invertebrate and vertebrate animals. It has generally been very accurate in identifying harmful alien species. However, the use of this system has revealed some potential pitfalls, with low accuracy when applied to aquatic species.

Advances in the field of risk assessment for alien species require the incorporation of knowledge from other fields with the latest findings in invasion biology. Much research is underway in regard.

Read the article:

Kumschick, S. & Richardson, D.M. (2013). Species-based risk assessments for biological invasions: advances and challenges. Diversity and Distributions DOI: 10.1111/ddi.12110

For more information, contact Sabrina Kumschick at