Mark Davis: Rethinking Invasive Biology

Mark Davis' 2011 paper "Don't Judge Species on their Origins" was not well-received by sections of the ecological community. But why is a call for rethinking our attitudes to invasive species so controversial?

In the series Norway’s Newcomers, we’ve looked extensively at not only Norway’s non-native species, but the genetics, definition and even the defense of alien species. So it made sense that we’d eventually find our way to interviewing an invasion biologist. I was in St. Paul, Minnesota earlier this year and was lucky enough to sit down with Professor Mark Davis.

Mark has been a strong opponent of the demonisation of invasive species for decades. Whilst many ecologists’ first reaction is to eradicate any non-native species, Mark has urged caution, and encouraged the community towards less pejorative terms. I spoke with Mark about the impact our work has on public opinion, how we should talk about non-natives, and living with the impact of invasive species going forward.

Sam Perrin: How has ecology changed over the last few years?

Mark Davis: I think ecology has changed enormously. 30-40 years ago, most of the research was done in wilderness areas where there wasn’t much human activity. Now an awful lot of research involves some sort of human activity. There are a lot of urban studies. Even the stuff that is in areas that are untouched by humans, the human aspect is factored in. For me, that’s by far the biggest change.

SP: Do you think attitudes to what we do have changed as well? How the public perceives us?

MD: That’s always been hard for me to tell, since I’m on the ecology side. There are still people that don’t believe much of science, who still don’t regard what ecologists say very highly. But the general public certainly has been swayed by the work of ecologists on non-native species. Ecologists took the lead on that, and the public eats in up like crazy.

SP: So that brings us to invasive species. How do you define invasive?

MD: The key thing at the beginning is to distinguish invasive species from non-native species. Some people still today use those words interchangeably, which is very unfortunate. If you look at the literature in the 1980s and early 90s, any non-native species was defined as an invader. That has changed over time. In this country at least, an invasive species is a non-native species which causes threat or harm in some way. That harm is either to human health, economic or ecological. But I know a number of people in other parts of the world who prefer the term invasive species to just mean a species that spreads a lot, irrespective of its damage or harm. So that’s always been a problem in the field, that there have been these two working definitions of what invasive species are.

Mark’s research group has recently been looking at the effects of garlic mustard, a non-native species in Minnesota. Despite the fact that it is thought to have very harmful effects on native species, Mark’s group has found no evidence of effects on native herbs, shrubs or tree seedlings

Mark’s research group has recently been looking at the effects of garlic mustard, a non-native species in Minnesota. Despite the fact that it is thought to have very harmful effects on native species, Mark’s group has found no evidence of effects on native herbs, shrubs or tree seedlings (Image Credit: Mark Davis, Macalaster College)

SP: The government’s definitions have both ecological and economic aspects involved. When there’s a clash between the two, how can we find a resolution?

MD: What’s not being done enough is to get public input. Harm is just a perspective. It’s easy to demonstrate threats to human health and economic harm. It’s ecological harm that is a very murky, grey area. What some people call harm is what other people call change. So that’s where I think the views of the public need to be taken into account. There may be a subset of conservationists that view this increase in non-native species and decline of non-native species as harm, but there’s no intrinsic reason why that should be harmful. It’s just a preference for native species.

But for the general public, change in abundance of local species isn’t necessarily harm. The problem with declaring harm is that you then obligate society to spend some money and do something about it. So labeling something as harmful is a very important act.

SP: Should there be a change in the language we use?

MD: Absolutely. The word alien, the word invasive, those are not scientifically neutral terms. They’re pejorative terms which essentially are already deciding what’s desirable and what’s not. They both have bad connotations, particularly now that they’re also used for humans. That’s always been a serious issue, it’s only finally being recognised by people in the field that there are problems with those terms, both with use for humans and for other animals.

I think the word should be much more scientifically neutral. You can talk about long-term residents, new arrivals or novel species, which is more descriptive, very neutral terminology, it’s not saying they’re better or worse. And then it’s up to the public to decide whether or not they should be termed harmful, or whether or not we will have to live with the change. Most of the changes we are going to have to live with, so you really have to pick battles very carefully.

SP: Can you tell me a bit about the nativism paradigm?

MD: Well the nativism paradigm goes back to the early 80s. It was the beginning of the field in invasion biology, with the concept of an invader being any non-native species. So restoration biology, conservation biology and invasion biology all embraced this notion that native species are preferred over non-native species. Restoration ecology’s explicit purpose was to get rid of non-native species and reestablish native species. Invasion ecology really provided that framework and paradigm, that native species are preferred over non-natives.

SP: I was at the Charr Symposium yesterday, and I heard a talk whereby they were citing the use of more emotive language in getting the public on board. With conservatives, they would talk about how things ‘used to be’. With liberals, they would focus on on the conservation side.

MD: I really am opposed to that approach. That’s just scientists manipulating the public by using terminology that sounds scientific but is just emotive language cloaked in what seems to be scientific language. It’s not being honest or straightforward with the public. It really suggests that the scientists know what’s best, and so we have to manipulate the public to come on our side. If you don’t feel the actual facts are sufficient then you have a problem.

MD: How should we be promoting objectivity in a discipline where bias is almost always inherent?

SP: I think the most basic way is the choice of language. Scientific language is generally not emotive. It’s not exaggerated, it’s not inflammatory. Just pay attention to the language that you’re using. I was surprised and disappointed that not many people in the field of invasion biology were aware of the use of emotive language and how unscientific that was. I think invasion biology is a really poor example of science, which historians and sociologists of science have in the past few years been noticing.

SP: On the other side of the restoration debate, there’s a push at the moment surrounding rewilding, bringing species back into areas they were previously native to. There have been pushes to allow the reintroduction of wolves to Scnadinavia, and Tasmanian devils onto mainland Australia. Is that a good idea?

MD: That’s a non-scientific question. Even if a scientist answers it, it’s not a scientific answer, it’s a preference. There is a similar issue on Isle Royale, just outside of Duluth on Lake Superior. They just decided to bring wolves back in, there were one or two left and they would have been extinct within a year. The wolves weren’t “native” there, they just went there in the past 100 years, just like the moose did. But that was the big debate, do we let the wolves back in and let nature take its course, or just let the moose population explode until they’re dying of disease and eat the rest of the spruce trees?

It was a debate within the conservation field. People had different views, because science can’t really answer that question, it’s a matter of values. And so they did decide to move in 30 wolves over a couple of years, which was my preference. But it wasn’t for a scientific reason, it was just that it was always such a nice research area. They’d have moose and wolves and could follow predator-prey fluctuations.

So it rewilding good or is it bad? It depends on the local situation. In some circumstances, the same individual may have different answers depending on the location. But it’s not a question that can be answered in an absolute way. And the key thing is to remember is that it’s not a scientific question, and a lot of people don’t realise that. They feel that scientists are making a decision that’s scientifically based, but preferences are not scientifically based.

Whilst invasion biologists are trying to assess the impact of novel species, other ecologists are suggesting the reintroduction of once-native species that have been driven out. But is it a scientific question?

Whilst invasion biologists are trying to assess the impact of novel species, other ecologists are suggesting the reintroduction of once-native species that have been driven out. But is it a scientific question? (Image Credit: JJ Harrsion, CC A-S A 3.0)

SP: We’re seeing species that are spreading further up, species moving into new ecosystems as a result of climate change. If we can stop this, should we?

MD: I think the idea of habitat museums is an interesting one. People like to go to museums, see historical towns and see things the way they used to be. The idea of having a display showing the way lakes or grassland was 150 years ago, or how it was 50 years ago and now, maintaining those would be interesting, but really that’s what you’re doing, creating time pockets. I’m not opposed to them, but they could only be on a small scale, because they’d be so expensive.

SP: In some circles these days, science right now seems to come under increasing skepticism. Are we doing a good job of communicating with the public?

MD: Apparently we’re not. It’s a great concern. The people who have thought and written about this, what they recommend is that you have to embody the science in stories. In stories that are meaningful to the people that you’re trying to educate and implore. I don’t think scientists are well-trained to do that, but pretty clearly, just communicating findings and facts, one would wish that were sufficient, at least for a lot of people. And it can even have the opposite effect, which is really discouraging. When you provide this information and facts and the people you’re trying to inform end up digging in their heels even more, and resisting anything you have to say. So it’s unfortunate that it’s proved to be such a challenge.

SP: Ian Winfield, who has been working with cultural anthropologists in an effort to reach out to the public, was talking at the same conference about the fact that often scientists are very cautious in using terms like ‘we know’. Because we don’t, by definition we strongly suspect something, whereas politicians will say anything. Do you think we need to start changing our language, or should we rely on the public to see through the falsehoods of their supposed knowledge?

MD: I mean the public for the most part only knows what it has access to, and if they’re getting “fake news” then that’s very discouraging, because for many people, they will believe and adopt that. Behind everybody there is ultimate bias. People have ideologies that guide a lot of their actions. For some people it’s politics, others religion. And they end up manipulating what they hear, or what they see through those tinted glasses. It can be quite discouraging. It’s a great problem. I think we need to seek the help of people outside the field, people in the social sciences, people in the humanities, who understand how people acquire information and attitudes, and work with them to try and disseminate our knowledge, in a way that is hospitable. That’s what I’ve heard from some of these people, that we need to encase our knowledge in stories, because that’s what people identify with, personal stories. And many scientists aren’t very good at that.

So if you have a paper that has tangible benefits for other farmers, for instance. If you take that and show how other farmers have used this knowledge, that’s how you get more farmers on board. Not by giving them a 95% confidence interval. But for so many of us, scientific communication means journal articles, and that’s one of the worst ways to communicate with the general public.

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