The Polysemy of Invasive Species

Yes, the Asian Carp are on their way
And life as is known can’t help but change.
But, really, if we must fish

For euphemisms—Who
Brought whose eggs and minnows
Here to invade whose waters, land, and

Purity in the first place?

- Excerpted with permission from Ed Bok Lee’s poem Super Insensitive Species

In my last post on Conceptual metaphor, I gave examples where abstract concepts such as happiness, love or time are tethered to the tangible through our language. In that post I said that similarly subtle metaphors exist in science as well. In Biomythic one of my objectives is to consider a series of these metaphors and show how they matter.

Lest I side-step my claim, consider as a first example the term ‘Invasive Species’. As Bok Lee satirizes in his poem above, the discourse around Asian Carp in the US feels like thinly veiled anger and resentment towards Asian Americans.

He starts his poem with a quote from a Scientific American article entitled “Invasion USA: Asian Carp Invaders Have Taken the Mississippi, Are the Great Lakes Next?”.

“Asian carp [introduced to control weeds and parasites] have been crowding out native fish, compromising water quality and killing off sensitive species.”

Reading the article begs the question: are we really talking about fish here or are we talking about immigration and race? Is the push to expel the Asian Carp based on appropriate scientific reasoning or are motivations and actions tinged with resentment not just towards a fish but to a people?

One of the species of Asian Carp that has moved beyond its original habitat¹

The Ambiguity of Metaphor

Metaphor can be open to readers’ interpretations and even to simultaneously afford multiple comparisons. In art, that’s its elegance and power. In the Western European tradition, how many English teachers and professors have asked students to consider this quote from Shakespeare?

Romeo: Here’s to my love! [He drinks] O true apothecary! Thy drugs are quick. Thus with a kiss I die.

Who is the ‘True Apothecary’ in Romeo’s final speech? Is it the chemist that sold him the poison or is it death personified? Maybe it’s both.

The term ‘invasive species’ has a precise definition in biology and ecology. But can we abstract it fully from its military history? When we hear the term ‘invasive’ at some level does it conjure other invasions we know: The Nazi invasion of occupied Europe? The Napoleonic Wars? The invasion of the South African Republic by the British Empire? The list is long.

But has using the term ‘invasive’ altered how we have addressed species that expand into a new habitat? The dictionary defines polysemy as “the coexistence of many possible meanings of a word or phrase”. Is the term “invasive species” then polysemic - bringing to mind not just carp but wars and conquest? And does that association alter our methods and approach to controlling these species?

It’s hard to quantify effects as metaphors like this function covertly. Yet the rhetoric in the field is intriguing. Consider a passage from a highly influential scientific paper in the field of ecology on invasive species that has been cited in a whopping 7000 subsequent journal articles:

“Eradication of an established invader is rare and control efforts vary enormously in their efficacy … [Invasive species control] is most effective when it employs a long-term, ecosystem-wide strategy rather than a tactical approach focused on battling individual invaders” 

Why does this passage feel like it came straight out of West Point? Look at words: eradication, strategy, tactical, battling, invaders.

Who’s Invading Anyways?

The term ‘invasive species’ does nothing to indicate our culpability in creating the challenge. We instead direct all of our anger to the species themselves in a classic case of externalizing the problem. Yet the vast majority of invasive species become such through typically one of several ways:

1. We import one invasive species to deal with another (i.e. the Asian Carp).

2. They tag along in the course of human migration or colonization (rats into Polynesia)

3. They are brought in for food or trade and go feral (rabbits in Australia, opossums in New Zealand).

4. They are introduced through our leisure activities (Zebra mussels adhering to the hulls of boats that are ported from lake to lake)

5. We import them for our pleasure as pets or plants and they spread when we no longer want them and release them (Anacondas in Florida, aquarium fish in lakes throughout the world).

All of these pathways share human introduction as a common denominator. Asian Carp do no strategize to conquer the Great Lakes. Nor do Zebra Mussels elect some aqueous Bonaparte to lead them. The term ‘invasive species’ subtly imbues these creatures with too much tactical intent.

What are these species fundamentally? I think of them as tag-along species or maybe hitchhiker species. But if my proposed new terms come with their own associations, why not simply call them introduced species?

These terms matter as we cannot turn back the clock to undo past mistakes. Many of our efforts to eradicate invasive species cause more harm than good. If we are going to apply tens of thousands of gallons of herbicide into a lake to kill an aquatic plant, let’s make sure our motivation for doing it is level-headed and not driven by some misplaced animosity towards Water Hyacinths!

This is not a new issue. Rachael Carson wrote in the 1960s about the ‘bludgeoning of the landscape’ through dumping pesticides in an effort to eradicate sagebrush in the US.² She was one of the first to document the myriad side-effects of this practice. Meanwhile, leading science textbooks still used today educate children with these metaphors and so indoctrinate the notion of humans and insects being engaged in an evolutionary arms race:

“Ever since humans began farming, they have battled insects that eat crops. Many farmers now use chemicals called pesticides to kill crop-destroying insects. When farmers first used modern pesticides such as DDT, the chemicals killed most insects. Today, farmers fight an on-going “arms race” with insects. Scientists constantly search for new chemicals to control pests that old chemicals no longer control. How do insects fight back? By evolving”.³ 

In Aotearoa New Zealand where I now live the issue of invasive species is frequently in the media. That the issue is particularly acute here stems from the land’s separation from the Gondwana landmass millions of years ago and the distinct evolutionary pathways species have taken across that vast time. This makes ecosystems here particularly susceptible to introduced species.

On the arrival of an international flight passenger bags are thoroughly checked for any camping gear that might harbor invasive species. In the lakes and streams Catfish are considered to be a major problem and there are significant efforts to eradicate them.

Meanwhile, in our first month here we were told by several people that if we see wallabies on the road (introduced from Australia in the 1800s) hit the accelerator and run them over. Having never seen a Wallaby outside of zoo, I’m not sure I would be able to take that advice.

A Red Necked Wallaby⁴

There are also many species of birds that are found nowhere else, which are significantly threatened by introduced species such as opossums and rats. To be clear, I am not taking a position on any of these specific control efforts. My enchantment at seeing my first Wallaby does not mean that I think those who seek their extermination cruel. The issues for any given invasive species are complex and intersect with culture, livelihoods and identity in ways that make it naive to treat it as simply a cerebral issue.

What I am proposing is the metaphorical framing of invasive species has likely caused people across the globe to approach these topics already intent on eradication. Not all invasive species cause harm and as climates and environments change, not all native species are harmless. Meanwhile, total eradication may not be the appropriate objective and should be considered along with efforts to limit but not eliminate spread.

Ultimately the value of a less pejorative term is so we can approach the continuing alteration of ecosystems with clear thinking, fully cognizant of our role in creating the problem. The history of humans addressing invasive species is often one where a given environmental problem is met through introducing some new eco-calamity. Metaphors such as invasive species likely function to limit needed discourse by channeling our anger towards a particular culprit and in doing so close us off to critical ecosystem perspectives.

1. JoJan at en.wikipedia, Public domain, via Wikimedia Commons

2. Carson, Rachel. Silent Spring. 1962, Available at https://archive.org/details/fp_Silent_Spring-Rachel_Carson-1962

3. From the bestselling textbook Biology. Available at http://millerandlevine.com/macaw/intro.html

4. By User:benjamint444, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2189793