Helen Roy discusses her recent Policy Direction, Developing a framework of minimum standards for the risk assessment of alien species and the challenges of producing a 14-step checklist for quality assurance in invasive species risk assessment.

The dramatic rise in numbers of non-native species worldwide is increasingly recognised as problematic. While some non-native species have minimal effects on biodiversity*, and a few may be beneficial, about 15% have unacceptable damaging consequences and are termed invasive non-native species. It is critical to ensure that the invasive subset of the non-native species are identified so that plans can be put into place to manage them. However, this can be difficult. Additionally, given limited resources available, it is necessary to prioritise invasive non-native species by ranking them, for example on the basis of the extent of their negative impacts. Evidence of impacts is often scarce. These are species that may not yet have arrived in a new region and so the nature of their ecological interactions within an invaded range may be yet to unfold.

Despite these constraints there have been many studies developing ways of assessing impacts which have contributed hugely to understanding of invasions. Furthermore, there have been many predictive models to describe the probability of a species arriving and subsequently establishing self-sustaining populations. Risk assessments endeavour to pull together all the information on the invasion process for a specific species using the best available evidence on introduction events, establishment probabilities, patterns of spread and potential negative impacts. Such risk assessments are a vital component of decision-making and underpin policies in invasive non-native species.

Many different risk assessment approaches have been developed. Some focus on specific groups of plants or animals, others on distinct environments and some for specific legislative purposes. In every case, considerable work is required to bring together the required information and, there are huge benefits for ensuring consistent approaches while recognising that one size does not necessarily fit all.

With funding from the European Commission, 35 European experts on invasion biology from 17 European countries came together through a collaborative study to devise a framework of minimum standards as a checklist for quality assurance. I had the pleasure of leading this group and enjoyed the lively and stimulating discussions that ultimately led to agreement that a risk assessment should comply with 14 minimum standards (attributes). Many of these are intuitive, a risk assessment should include a basic description of the species and how likely it is to invade, spread and have negative impacts on biodiversity. However, socio-economic impacts are also important and, while the invasion community has struggled to consistently assess biodiversity impacts, socio-economic impacts seem to be even more tricky to assess (although there has been huge progress with the recent publication of SEICAT). It is exciting to see new ways of tackling these difficulties including through the development of innovative statistical models.

So the agreed minimum standards were:

1. Basic species description
2. Likelihood of invasion
3. Distribution, spread and impacts
4. Assessment of introduction pathways
5. Assessment of impacts on biodiversity and ecosystems
6. Assessment of impact on ecosystem services
7. Assessment of socio-economic impacts
8. Consideration of status (threatened or protected) of species or habitat under threat;
9. Assessment of effects of future climate change
10. Completion possible even when there is a lack of information
11. Documents information sources
12. Provides a summary in a consistent and interpretable form
13. Includes uncertainty
14. Includes quality assurance

We hope that this framework of minimum standards will be beneficial for people involved in prioritising non-native species to inform effective decision-making. The opportunity for so many experts to work together to derive this list of minimum standards enable sharing of ideas and concepts from far-ranging perspectives. During the consensus workshop, in which came together for two days, we had exciting discussions on topics that have relevance beyond risk assessments. Communicating uncertainty is an issue that scientists from many disciplines are grappling with. Thinking to the future we need more rigorous ways to capture the ways in which climate change may affect invasions. And that is exactly what we are doing. Today I leave for a meeting in Brussels where I will lead a workshop on prioritising species through risk assessment and including the very latest climate modelling approaches embedded within the minimum standards.

I would like to thank the European Commission for funding this research through the project “Invasive alien species – framework for the identification of invasive alien species of EU concern ENV.B.2/ETU/2013/0026”. My gratitude also to all my amazing collaborators who are simply inspiring.

*Invasive non-native species can also have negative effects on society and economies as well as biodiversity.

The full article, Developing a framework of minimum standards for the risk assessment of alien species is free to read in Journal of Applied Ecology.

Learn more about Policy Directions in the journal.