​​​​​​Professor Chad Hewitt, of the University of Waikato, has a background in advising both the Australian and New Zealand governments on risk assessment and biosecurity management. On Thursday's open plenary of the Annual Science Conference in Riga, he gave a detailed insight into the challenges regarding the management of marine introductions and the struggle we are facing when trying to evaluate the appropriate response to future bioinvasions.

Over the last 100 years, the number of introduced species has accelerated immensely. Some of these invasions have economic impacts or they affect our livelihood, health, and well-being. Hewitt emphasized the importance of prevention and risk reduction as a measure of dealing with invasions, especially in the marine environment where our ability to detect a possible future impact is low.

How many species are currently in play?

"Unfortunately, they [bioinvasions] don't come with tags," Hewitt noted. Determining whether a species is introduced or not is not easy. A global assessment done in preparation for advice to the Australian government estimated that 2365 marine and estuarine species had a recognized invasion history.

"Today, we know that this number is actually closer to 2700, but this was still an underestimate" he said. And still, this is only talking about the recognized species that have been declared non-native. The fact that everything is connected becomes undeniable when looking at large bioregions, including the Antarctic and Arctic.

"The supporting knowledge base is relatively poor, and there is a tendency of perceiving the problem of marine invasions as being too big. We act like a "stunned mullet" – and do nothing."

However, we need to look at these bioinvasions as large scale experiments and it is necessary that we keep our focus on the future, Hewitt pointed out.

"We are not going to eliminate 2500 species from the world's oceans. We can, however, look at those and learn about where they are likely to arrive next, and which ones are the most important for us to manage."

The challenges of marine biosecurity

Hewitt pointed out that the art of marine biosecurity is to ask four simple questions: "Which species are of concern?", "Which are going to be next?", "What are the most important transport vectors", and "Which pathways are of most concern?" The questions are simple; finding the answers is not.

When undertaking a consequence assessment, the question becomes "What do we want to protect?"  Hewitt underlined that this decision is both ecological and socio-political: What do we value and why do we wish to protect these elements?

"The focus must be on understanding what constitutes impact, how we categorise impact, how we measure this in the field, and how we communicate this to political stakeholders," Hewitt stressed.

Scientists versus managers – the approach to bioinvasions

Hewitt pondered whether, in the presence of uncertainty, scientists would be precautionary. This is as opposed to managers, who have an economic and political incentive to be careful but to be non-precautionary.

"We explored this both in the US and Australia and I'm sorry to say that all of us [scientists] were very non-precautionary. All of us in the presence of high uncertainty chose to deem the species to have low impact," he concluded.

Another strong point he put forward was about the statistical bias that is almost always employed: "A species is innocent until proven guilty. We will intentionally not deem impact unless we can prove it beyond a shadow of a doubt".

"The unfortunate element here is that the manager, or even more importantly the politician, will say that no evidence of impact is equivalent to no impact. And I think we need to be very careful about how we communicate this into the future."

What are our needs?

Hewitt stressed the importance of communicating with stakeholders in a way and language that they understand.

"My personal feeling is that we are now at the point where understanding impact and being able to predict impact is critical to the dialogue with political stakeholders and the public The question is no longer 'Do they [introduced species] cause impact?' but 'Do they cause unacceptable impact?'

He also pointed out the importance of global collaboration networks.

"I want to know if the species you have that may arrive in New Zealand cause harm. You have to do the research. I can't do it. We need that reciprocity".