"Invasive Species": The Widening Gap between Popular Belief & Science
Don't believe the hype
This is just a quick reflection I want to share.
As I've been mentioning here, my main winter project has been working on a book with Nikki Hill, tentatively entitled, "Don't Blame the Messenger: A critique of the 'invasive plant' narrative." As part of that effort, I've been reading lots of scientific papers in peer-reviewed journals from invasion biology and other fields, and it's been really eye-opening.
The popular narrative of "invasive plants" is really black and white: These are bad plants. They don't belong here. They cause harm to native plants. They're upsetting the balance of nature. They must be eradicated.
It's a scary monster story and a militant call to arms rolled into one.
But the science is far more nuanced. The amount of debate and the lack of consensus within the field is quite striking, actually, and has been growing over time. Invasion biology as a distinct area of study only goes back to the early '80s and didn't really take off until the '90s. Given this short history, it's possible to get a picture of where it was and where it's going, and where it's going is further away from the heroes and villains trope. (Great song but not a very good way of looking at ecology.)
As I said, this is just a quick reflection, so I'm not going to provide a bunch of links and citations—that's what the book is for, after all!—but I want to throw a few things out there that I've been reading about lately.
Except for a small number of people in the late '90s, nobody in the field of invasion biology is saying "native=good and non-native=bad." That's just not a thing in the science. The consensus in the field is that only a small number of introduced plants are able to successfully establish themselves in a new setting, and of those only a small number cause "harm." What constitutes "harm," though, is a subject of lots of debate, and the most easily demonstrable harm is economic not ecological. Think crop yield decreased by introduced weeds, insects or pathogens. Some scientists make the argument that "harm" is not something that scientists should be deciding period, by the way, as they consider the concept completely subjective.
The number of native plants that have gone extinct in the US—or even in just one US state—due to competition from an introduced plant is 0. None. If we're talking "invasive" threats to native plants, the issues are predation (eaten by animals) or pathogens. But predation includes being eaten by native animals, too, as when deer populations blow up because we've killed all the predators like wolves, mountain lions, etc.
Although plant "species richness" (number of species) at the global scale has been declining due to human activity, the species richness at local scales has been increasing due to the introduction of so many new species. So, pretty much wherever you are when you're reading this, you're in a region that has more species of plants now than it did before 1492. That's not higher "biodiversity" since that word refers only to native plants, but it's higher diversity in terms of plain old raw count. An increasing number of invasion biologists are saying that this higher species richness can have benefits for native wildlife. (More food for herbivores, more pollen sources for insects, etc.)
Intriguingly, species richness of native plants is, overall, higher in "invaded" areas than non-"invaded" ones. (Okay, I'll provide a citation for this one since it might strike some people as counterintuitive: "Non-natives are linked to higher plant diversity across spatial scales" in the Journal of Biogeography, Feb. 2024.)
Note the date on that. February of this year. Some of the most interesting findings have been in the last decade, or more recently, and they haven't yet percolated out of academia (if they ever will). The pop culture "invasive" narratives dates back to the '90s, and hasn't really changed much since then unless it's gotten more extreme. But there's been lots of new research since then, some of it due to new technology. Online databases and more computing power allow for document search and data aggregation that was virtually impossible before when it would've meant spending countless hours going through physical journals by hand or squinting at microfiche and then painstakingly figuring out calculations. So some of the most interesting papers of recent years have been meta-analyses, where the data is crunched from hundreds and hundreds of studies, yielding big picture views not revealed previously. Some older hypotheses from the field have not been holding up under this examination.
Speaking of recent papers, today I read "Systematic and persistent bias against introduced species"Â from the January issue of the journal BioScience. This meta-study confirmed what many people inside and outside invasion biology have long believed to be true, which is that "conservation science is biased against introduced species." (And this 2017 paper, though it uses different methodology, says such bias has been decreasing since the mid-2000s.)
It's worth quoting this paper's "Conclusion" paragraph in full:
Our results confirm that the narrative of introduced species as an environmental problem remains entrenched. However, there remains a persistent portion of the field who choose to frame introduced species in neutral terms, and the rise in new voices that value introduced species as part of Earth’s biodiversity is noticeable. We look forward to evidence of a decline in the bias against introduced species. Invasion biologists have defensively argued that criticism to their field is a form of science denial (Russell and Blackburn 2017a). Rather, what critics of invasion biology have objected to is the consistent and persistent efforts by many in the field to characterize introduced species in a negative way. Scientists should always be cautious when ascribing value to empirical observations, should maintain an open mind when setting out to describe the complexity of the living world, and should apply critical thinking, particularly when views become entrenched. We hope this study promotes openness, debate, and pluralism in conservation.
So, the field is engaging in self-examination (and self-correction according to the second paper), which is what good science is supposed to do. It’s my hope, of course, that my own efforts in writing on the subject will lead to similarly positive shifts in the popular narrative.
On a logistical note: One challenge to researching scientific literature is that much of it is behind paywalls that are quite expensive. Like $30 per paper expensive. I've got no budget for even one paper at that price, so here's three pro-tips I have to offer:
academia.edu and PLOS ONE both host papers that are freely accessible. You can search on your topic of interest at both sites.
If there's a paper you want that's not freely accessible, but you know the title, I've heard that you can check for it at Anna's Archive, a foreign-hosted, gray area website which you can find through an internet search. I am just passing this information along, not making an official recommendation.
You can also write directly to a paper's author and request a copy, as they have the right to share it with whomever they want. That's how I got the "Systemic and persistent bias" paper. I told him what the book project was about, and he included another paper he authored that he thought I would find helpful, which was cool.
Well, back to the reading now, but I wanted to poke my head up for a minute and share some thoughts.
