The Norwegian Biodiversity Information Centre has the task of assessing the ecological risk posed by non-native (alien) species in Norway. This risk is assessed using a standardised quantitative method, first developed in 2007, in Norway, and subsequently refined for the ongoing assessment of alien species.

A pioneering methodology

Due to the lack of an internationally recognised methodology for the risk assessment of alien species, Norway has developed a standardised method that is quantitative. This means that numerical values have been used to determine the ecological impact of a species on Norwegian nature, rather than subjective terms such as high and low. This method, described in "Guidelines for the Generic Ecological Impact Assessment of Alien Species" is also generic, meaning that the criteria can be used for all organism groups.

Development of the first method – 2007

The first generation criteria were based on qualitative assessments of ecological effects and the assessments of selected species were published in 2007, in "Norwegian Black List – Ecological Risk Analysis of Alien Species". The probability of introduction, dispersal and impact on native species was described in three categories: 'high', 'unknown' and 'low'. Such qualitative assessments contain a high degree of subjectivity, and the assessments are difficult to replicate.

Collaboration and the move toward a quantitative method – 2012

In consultation with the Norwegian Biodiversity Information Centre, the Centre for Conservation Biology (now the Centre for Biodiversity Dynamics) at the Norwegian University of Science and Technology (NTNU) began the process of developing a standardised methodology. This method laid the foundation for the second ecological risk assessment of alien species in Norway "Alien species in Norway – with the Norwegian Black List 2012". This method was based on a semi-quantitative set of criteria ie. verbal descriptions, not numbers, were used to delimit categories for some of the criteria.

Stakeholder input and ongoing refinement of the method – 2014-2016

Subsequent to the risk assessments conducted in 2012, the Norwegian Biodiversity Information Centre sought input from users, experts and relevant authorities to further improve the method. Particular attention was given to understanding the needs of users. In 2014, a reference group was established to work on refining the method. A call for public contributions regarding the method, and criteria, was then made in 2015.

A robust quantitative method – 2018

The method used for the 2018 assessments is entirely quantitative (based on numerical values). A complete overview of the method used in 2018 is published in "Guidelines for the Generic Ecological Impact Assessment of Alien Species, version 3.5". This document also contains a summary of changes to the method (2012-2018) that apply primarily to the delimitation (historic, geographic, ecological and taxonomic) of an alien species. Some criteria threshold values have also been adjusted and the calculation of expansion has been refined. In response to the needs of users, uncertainty is now visible in the assessments; geographic variation has been taken into consideration; and a selection of regionally alien species has also been assessed.

Beyond borders – a contribution to alien species risk assessment in Europe

The development of a methodology and the work that Norway has done on alien species has been noticed in other countries. The Norwegian method GEIAA (Generic Ecological Impact Assessment of Alien Species) has been an important contribution to the work with alien species in Europe. It is particularly interesting that Sweden, in their first approach to assessing ecological risk, has made use of the Norwegian method.