I learned early on that there are good species and bad species. The good species make for excellent stuffed animals and cereal box mascots: tiger, bear, honeybee. They can be heroes like the bottlenose dolphin or victims like the American chestnut. For years, my favorite animal was the peregrine falcon—the fastest bird in the world—and I still have the t-shirt to prove it.
The bad species are fewer but loom larger in everyday life: weeds in the garden, pests in the house, poison ivy. I’ve known many a New Yorker who loves to hate a subway rat.
My relationship with bad species goes back to childhood in San Diego, when my mom would turn me loose in the yard with a special mission: eradicate sea-lavender. My weapon of choice was a weeding fork with a long wooden handle. It was designed to lift plants out of the ground from below, but most often I wielded it as a sword. As the garage door drew open, spilling sunlight into cobwebbed corners, I imagined myself a jedi going to battle with an alien foe. My Pop-pop had told me that plants can sense others of their own kind and that if you cause enough damage to a few, it will discourage the rest from growing. So I spent afternoons mindlessly hacking away at terrible, menacing, beautiful purple flowers waving above lettuce-like foliage. I left my victims on the battlefield as examples to their terrified comrades. Ironically, I proved to be an efficient disperser of sea-lavender seeds, but I only saw their continued proliferation as further evidence of villainy.
Many years later I learned I had been up against no ordinary adversary, but rather a member of a special club that makes a profession of badness. If garden weeds are the common criminals of the species world, invasive species are the mob bosses, the megalomaniacs, the supervillains bent on global domination.
Discovering invasive species supercharged my relationship with the natural world. Suddenly, on every street corner and in every park, I was on the hunt for villains and their victims. This golden- rod isn’t a weed. It’s a native species! What’s this cute plant trying to charm us with its pendulous white blooms and soft green foliage? Thank god I know that it’s actually an INVASIVE SPECIES! Rip it up! Dig it out!
The more I obsessed, the more I was drawn into an astonishing universe of rogue superorganisms that somehow thrive despite our best efforts. The wicked problem of invasive species grew in my mind, until I reached an unexpected impasse:
What if there are no supervillains in this story? What if there are only random plants and animals just trying to do their best to survive and reproduce in a world beset by rapid environmental change?!
* * *
It’s early March, and I’m in Burlington’s Centennial Woods with naturalist Teage O’Connor. As we descend into the leafless forest, I can’t help starting a list of offending species that catch my eye: burning bush, bittersweet, barberry...I know them better than I know the trees.
“Common buckthorn is incredible in its ability to persist in heavily disturbed soils,” Teage says. “But if we end our curiosity towards it by labeling it, we stop figuring out what makes it so incredible at what it does.” Snow crust crunches underfoot as we walk, and Teage recounts random acts of violence he’s seen perpetrated against buckthorn: “It’s like this knee-jerk reaction against a species you’ve been told shouldn’t be anywhere. If your primary relationship with invasive and non-native species is adversarial, there is a barrier against you appreciating the landscape for what it is.” I remain silent—he could easily be describing me.
We arrive at a patch of tall reeds, where a small clearing on one side of the trail betrays secretive work. Teage is building a phragmites canoe—he plans to paddle it down the Winooski River from Salmon Hole to Lake Champlain. “The nice thing about invasive species is that nobody cares about them, so you can harvest with impunity.” He grasps one of the tan-colored stems, pulls up, and kicks the base of the dry reed, popping it cleanly out in one piece.
He reminisces as he works; this area used to be a flooded beaver pond with boneset, jewelweed, and dozens of hummingbirds during the autumn migration. “That’s all been crowded out by phragmites now that it’s gotten drier,” Teage laments.
I wonder which came first: the departure of the beavers or the invasion of Phragmites australis. Regardless, the spread of invasive species across Centennial Woods has become entangled with Teage’s emotional response to the loss of past experience in this landscape. But instead of cultivating animosity, he is busy finding ways to shift his relationship with these living symbols of undesirable change.
Teage started making Norway maple syrup after observing the local squirrels biting holes in the bark, as they do with native maple trees, to force sap to flow and sugar to concentrate through evaporation. It’s turned into a sunny afternoon, and as we scramble down a wooded slope in search of a squirrel-tapped tree, we find that the temperature has climbed into the upper 30s, just enough to start the sap flowing. The taste is mild, with only a hint of sweetness, but I still feel a twinge of new appreciation for Norway maple—a plant that I’ve hated for over a decade.
By prioritizing positive engagement with invasive species, Teage hopes to inject greater nuance into the conversation about their management. “I want people to be able to ask if it is really effective and necessary in each situation to get rid of them, and the ecological impacts weighed against all of the other ways of connecting with and experiencing a non-native species.”
“I wish, from a pop science perspective, that the term invasive species would just go away, because it becomes too easy to demonize groups of vastly different plants and animals without any context or scientific literacy. Most people couldn’t even identify the species they’re supposed to hate.”
* * *
Charles Elton, famed English ecologist, lived through World War II. When he published The Ecology of Invasions by Animals and Plants in 1958, it was filled with the imagery of military conflict: “It is not just nuclear bombs and wars that threaten us... there are other sorts of explosions.” In its pages, Elton wrote about “ecological explosions,” rapid proliferations of organisms, often those displaced from historic ranges. Malarial mosquitoes from Africa to South America, chestnut blight from Asia to North America, sea lamprey into the Great Lakes through the Erie Canal: trans- located species can pose serious threats to human health, biodiversity, and economic interests. Elton framed the struggle against invasive species as a battle for the fate of the world, a conflict that ecologists might ultimately decide.
But while introduced pathogens and pests may create harms that are easy to define and quantify, such as decreased agricultural yield or increased illness, most introduced plants and animals produce ecological impacts that are harder to qualify as wholly bad or good. In recent decades, some scientists have challenged the assumption that invasives are intrinsically harmful and have urged peers to eliminate biased characterizations of invasive species in scientific literature.
Nevertheless, public perception of non-native species is strongly influenced by a half-century of research that follows from Elton’s war-like framing of invasion biology—research that largely focuses on negative impacts of introductions and excludes benefits such as food and fuel production, climate change attenuation, and cultural value.
The language of invasion biology is itself a source of public confusion, as regular scientific use of loaded terms like “alien,” “exotic,” and “invasive” obscures the objectivity present in much invasive species research. These terms readily map onto xenophobic pat- terns of speech, either fueling hatred of non-native species or mis- trust of seemingly prejudiced scientists.
Furthermore, deciding what constitutes an invasive species is not straightforward. While scientists have historically used “invasive” to describe the biological behavior of introduced populations of organisms, governments define invasive species based on a perceived likelihood to cause economic or environmental harm. Even the terms “introduced” and “non-native” sometimes fail to provide clarity, as some invaders, like the barred owl in the Pacific North- west, were not spread by humans but merely expanded their natural range in response to climate change and landscape alteration.
For those who consider embracing a position of tolerance towards non-native plants and animals in the wild, another complication exists: introduced species usually undergo a significant lag time before becoming invasive, leading to guessing games about the long-term impact of species that have yet to prove problematic.
So where does that leave land managers, conservationists, and concerned citizens? When do we act to control introduced species and when, if ever, is it okay to stop meddling in the uncertain outcomes of invasion processes?
All along the Winooski River, silver maple branches arch grace- fully downward under the weight of a wet spring snow. The forest floor is buried, and only a few stems of last year’s growth hint at what lives in the understory. Duncan Murdoch is the Intervale Center’s natural areas stewardship coordinator, and he was here in 2015 on his first day on the job, cutting through a thick stand of Japanese knotweed. Over eight years, that stand has been replaced by a diversity of native plants. I ask how he managed to beat the notoriously persistent weed.
“Oh, knotweed is still here,” Duncan says. “So we just need to keep coming back, but the stewardship is getting less and less every year. We harvest it in the spring to make knotweed ice cream.” A downy woodpecker lands on a snag nearby and we pause to watch.
“I don’t think we’ll ever be able to eliminate them from the land... why should we?” he continues. “But we should watch them and we should control their populations sometimes, and I think the big reason is biodiversity.”
Duncan sees invasive plants as teachers, bringing people into closer relationships with the land. “They’re saying, ‘Pay attention! Look at your influence and how you are interconnected.’ We’re not here just to conquer the natural world but to take care of it and be part of it.”
We follow a pair of ski tracks downstream to another restoration site, and Duncan rattles off the lengthy list of invasive plants that he’s found on-site. “It’s like a combination of art and science, and it’s up to the land-user to figure out. How do you choose what to address? I’m trying to be comfortable not knowing the answer, and it’s humbling.”
Duncan launches a snowball into the air, and we watch it drop into the river with a satisfying plop. I’d like to ask the Winooski what she thinks about knotweed and native species, but she doesn’t stop to talk. The river flows ever lakeward with a swift, silvery boil in the morning light.
“Some of these plants have naturalized...when does that happen?” Duncan asks. “Is it just because we kind of like the plant and are all right with it?” Naturalized, invasive, alien: when released from the curated confines of academic papers, scientific definitions blend with intuitive meanings, and each word becomes no more than one person’s best attempt to describe a part of the messy natural world as they see it.
Duncan sees a middle ground.
“Goutweed is the entire forest floor in some areas, and I don’t see how we can do anything about it. So, we’re starting to do research around the relationship between natives and invasives, and I’m re- introducing ostrich fern. What native plants can compete?”
Shifting away from a paradigm of necessary eradication towards one of managed co-existence feels like a sea-change for me. De- militarizing my relationship with invasive species doesn’t neces- sarily mean embracing apathy or denying scientific consensus— but it does mean changing my expectations of what is included in a natural community.
“Nature will work itself out,” Duncan muses. “It’s just a matter of how it impacts us humans and our feelings about that. We’re here in such a small period of time, but nature thinks on such a grander, mind-blowingly slower scale, so really...it’s selfish I think... We’re doing this for our own good. To feel good. To be in an environment on our planet that feels right for us.”
The dirt road that bisects the Intervale has been plowed, and the snow is already melting off as we weave our way back around muddy potholes. As we pass farms and gardens, I automatically start another tally of invaders lurking in their hedgerows: burdock, bittersweet... but this time I stop. These bad species are the reason I’m out here, and I owe them a debt of gratitude.
