That’s an excerpt from a 1938 CBS Radio Network broadcast of War of the Worlds, a fictitious story by HG Wells chronicling a worldwide alien invasion. The broadcast was a live dramatization; however, the narrator, Orson Wells, framed the story as a piece of news occurring in real-time. That sent some of the American public into a panic, inciting a few terrified citizens to contact authorities in fear of an actual extra-terrestrial invasion.
The human fear of interlopers is a persistent theme in our history. Even outside of green men from outer space, we are locked in a perpetual struggle against species encroaching upon our own little world. We have given certain plants and animals the moniker “invasive species,” but much like HG Well’s novel, this is an invasion we created. Therefore, the pressure is on us humans to stop invasive organisms before they wreck natural and agricultural ecosystems.
You’ve probably heard this term before: invasive species. Caleb Roberts is a U.S. Geological Survey research ecologist at the Arkansas Cooperative Fish & Wildlife Research Unit, which is based in the UofA’s Biological Sciences Department. He said invasion ecology, or the study of invasive species, is a relatively new field:
“Humans have been moving around critters and plants since we've been moving ourselves around,” Roberts said. “But that was always looked at as a benefit, right? We move corn around, or we move whatever crop we have around right? So we never really considered that it wasn't until we sold sort of started seeing some harm from it. So we started to consider how, what we might call invasive or not”
In 2016, The federal government passed an Executive Order titled “Safeguarding the Nation From the Impacts of Invasive Species.” The order laid out specific definitions for what we call “invasive species” and “non-native” or “alien” species.
Non-native organisms are those that occur outside of their indigenous habitat because of deliberate or accidental human activity. Non-native or introduced species become invasive when they start to cause harm.
But Roberts said this understanding can become muddled when you consider:
“It's completely defined by us by humans, right?” Roberts said. “There's no like, objective way of saying what is invasive and what isn't. But there are some sort of general generalities, right, so one of those is geography: is this species from this continent, is the species from this region? Those are things that can make things non-native. And then, if they are aggressive in that they have negative impacts from our perspective, that can also register as an invasive species. If there's some sort of historical reason why we would think there is, you know, that could be a reason why, and then also the sort of genetics behind it, you know, are these things a different genotype or whatever from the native stuff.”
Some of these non-native, invasive species now call Arkansas home. Feral hogs cause farmers anguish as they destroy agricultural land. Kudzu covers swaths of hardwood forests, choking native species and starving them of sunlight.
Invasive species have caused over $1.2 trillion in damage across the globe over the past 50 years. Roberts said the people losing money are desperate to find a solution to these threats.
What’s more, invasive species are highly adaptable and aggressive, and they actively imperil the survival of native species by disturbing an ecosystem’s natural balance.
Roberts and his research team have dedicated their work to mitigating the dangers invasive species present. Earlier this year, Roberts’ team received a $650,000 federal grant from the Department of Agriculture to develop an early detection system and rapid response framework to combat the impact of invasive species across the country. He said anticipation is key in a battle with natural forces.
“The best way to deal with invasive species is to deal with them before they get there, or barring that, deal with them very early on in the invasion process,” Roberts said. “That is the most cost-effective and successful way to do it. And part of that is, you know, detecting them early on because when they first get here, you know, they're pretty rare. So you need to be able to sort of find them quickly. And then, if possible, eradicate them. That's where the rapid response comes in. So we're trying to develop a sort of nice standardized system that incorporates some of the aspects of invasive species ecology and also motivates the rapid response by quantifying the impact ecosystem services of the invasive species and then sort of mapping that onto where they're going to be and where they are.”
Roberts’ team is currently focusing on cogon grass, a warm-season perennial grass with saw-like edges and a love for fire. Biologists consider the plant to be one of the worst invasive species in the world. It was first introduced intentionally in Florida during the 1930s to be used as a packing material and forage for livestock. Scientists discovered the species in Arkansas in 2021 near West Helena.
"It's kind of one of those disaster plants, very difficult to kill."Caleb Roberts
Roberts said cogon grass is a good species to use as a starting point for examining other invasive plants and animals due to its range and adaptability.
“So, the tricky thing about invasive species is they're very surprising,” Roberts said. “So it's, I will sort of hedge myself a little bit and then say, there are some places where it probably won't be. But there's, it's all there. The other thing about invases are very surprising and adaptable, because it's, it may be sort of weird to think about this, but an invasion happens multiple times. There are, at least what they call them, propagules: the sources of the invasion. So, cogon grass's native range stretches from Australia all the way to southern Japan. And, you know, as you might expect, that the genetics of the species is different across that range, right? So, there have been introductions of cogon grass from different parts of its range and the different parts of the US. We have also cultivated a strain of cogon grass that is sold for horticultural purposes, which is supposedly sterile but has been known to become unsterile within a few generations. So you've got this recipe for a highly adaptable species that, you know, this sort of sub-tropical tropical in its native range, but as recently as of last year, been seen in Boise, Idaho, so somehow it's able to adapt to that. So it's difficult to say where it won't be, probably won't be in a straight-up desert, probably won't be in the swamp. But there's like, other places that appear to be fair game.
Cogon grass’ adaptability is matched by its hardiness. Roberts said the grass also has a propensity to snuff out other plants and animals.
“It's kind of one of those disaster plants, very difficult to kill,” Roberts said. “You have to really whack it with herbicide. You can treat it with fire, but it also sort of likes fire, and it burns very hot, and it'll regrow. It's clonal, so it goes through tillers under the soil outward from the point. So it's a big monoculture clump, right? So that means that basically nothing but cogon grass grows within the clump. And it's bad for timber production. It is very flammable. So that's also a risk for humans. It's not palatable for livestock. And there's been fewer studies on its effects on biodiversity. But there's some some work that showed that it's bad for plant biodiversity. And it's almost certainly bad for ground nesting birds' diversity, or things like quail and turkeys probably are going to dislike it.”
He said they’ll use statistical modeling software to map out landscapes that cogon grass has infested in order to predict where it might spread.
“So we have records of where cogon grass is and has been, right?” Roberts said. “And we, in the United States and elsewhere, can say where it will likely be in the future based on just how far can it disperse. How far can the folks spread it? Because they can be spread by people. So those are some sort of basic things, but there are also environmental factors that are making it more or less likely to be there. So, for instance, how close is it to a road? it's been very well documented that lots of invasives and cogon grass, too can be easily spread by roads, like mowing on roads. And this matter of fact, that's where it was first noted along a, I believe, a median in West Helena, so and then you know, things like climate, the land cover that's around at the soils, those are all things that will contribute to whether it will or won't be there. So you have all that information. And then you can use, you know, some sort of magic of statistics to predict where it will be in the future.”
The project is still in the early stages of development and research. Roberts said factors like climate change make predicting the path of invasive species more complex:
“One of the big debates is, are these species adapting while they're here because we've had so many of those propagules?” Roberts said. “Like I said, so many individual introductions of different genomes, essentially, from the species? Does it mean that we have artificially increased their genetic library so they can just flip through the pages and find the right combination of things so they can deal with Boise, Idaho? They wouldn't have been able to do that in their native range, right? So there are all kinds of reasons also, you know, we've genetically modified, you know, we've been selectively breeding this cogon grass and many other invasive species to be very adaptable to lots of different environments, right. So sometimes, we create our own worst enemies with invasive species.”
JT: Wow. And climate change just adds another piece of the puzzle, right?
“That's right,” Roberts said. “Yeah. You know, I tell this to my class, but you know, there's that quote from Jurassic Park, you know, ‘Life will find a way.’ I mean, really, that is like the thing about invasive species: they are very adaptable. And the soon as you think you've got them figured out, you're probably going to be wrong.”
