Invasive Species and the Trolley Problem

The trolley problem is a famous thought experiment meant to explore the realm of ethics. The typical framing goes something like this: a runaway trolley is barreling down the tracks towards a section where five people are trapped, but you’re standing at a switch that, if you pull it, would move the trolley onto another line that only has one person trapped.


You’ve got two options: do nothing as the trolley rolls over five people, or take action to save their lives, having to live with the fact that you are responsible for the poor soul on the other line. I'm going somewhere with this, I promise...


Governor Reynolds declared June in Iowa “Invasive Species Awareness Month,” which makes the topic for this month’s blog post an easy one. For those of us working in natural resources, sometimes it feels like it’d be better to have an “invasive species amnesia month,” because frankly most months we have a hard time turning it off.


Ahhh, parsnip.

June presents a great opportunity, since many of our most pernicious invasive species make themselves more obvious in the spring and early summer. The ability to start photosynthesizing earlier and continue later, or perhaps in a wider range of conditions, gives them the leg up needed to crowd out native species.


Garlic mustard going to work before the snow has melted

Not every non-native plant or animal automatically earns the “invasive” label. Game hunters introduced Ring-necked pheasants from China and East Asia, but no one calls them invasive. “Wild” asparagus grows from escaped garden stock, but again, rarely rises to the level of invasive status. Prior to the introduction of rainbow and brown trout, Iowa’s trout streams harbored only brookies.


Conversely, many states have tagged ragweed with the noxious weed label, even though those states encompass part of its native range. Whitetail deer, since dwindling to near-extirpation in the early 20th century, have expanded in population to the point where they meet at least half the definition of invasive – “causes or likely to cause economic or environmental harm.”



But they’re native. But then again, they were nearly gone, and we made a concerted effort to bring them back, and they only continue to thrive because of “unnatural” conditions allowing their proliferation – abundant food from crop fields, a lack of predators created by their extirpation, carefully managed hunting seasons, etc.


So the concept of an “invasive species,” like pretty much all of ecology, does not have a clear and concise definition. The amorphous nature of the phrase has led to a situation where nature lovers have adopted wildly divergent opinions on just what we should do with our awareness. The one thing everyone can agree on is that invasive species contribute meaningfully to the ongoing biodiversity collapse.


A mass extinction, visualized

Opinions diverge because in a way, invasive species present the trolley problem, and the trolley problem has no objectively correct solution. It all comes down to individual moral philosophy – the extinction train is rolling down the tracks. As land stewards, we have to decide whether we have an obligation to steer that train towards the path of least harm, or stay out of it to avoid direct responsibility for loss of life.

On one side of the coin, you have the advocates for passive rewilding. The phrase has become popular among many ardent preservationists, particularly in Europe, based on the concept that nature can heal itself if we just get out of the way.


The idea makes a certain measure of sense. Evolutionary history consists mainly of punctuated extinction events – like the one underway now – separated in time by long periods of uneasy dynamic equilibrium. And in some ecological contexts, the passive approach seems to be working pretty well.


This is the crowd that, in casual conversation about habitat improvement projects or natural resource management, will ask a simple question – why bother?


A totally fair question. Bothering often feels like throwing punches at the ocean. Often we can only hope to slow down the advance, taking a defensive posture rather than truly making any kind of headway. And of course, it's not cheap.


It's also not easy.

Further complicating the matter, passive rewilding advocates often point to a rapidly changing climate making the idea of restoring “natural” conditions an impossible task without some Bond villain-style atmospheric engineering. We’d be trying to save native species so they can persist in a world at odds with their own evolutionary history.


I sit firmly on the other side of the coin, and not just because of my chosen profession. Climate change has accelerated rapidly in the last fifty years. Drastic alterations to land cover have all taken place mostly in the last 150 years here in Iowa. Even the Columbian exchange, the most recent occurrence of mass transfer of species and genes between continents, began just some 500 years ago.


Meanwhile, oligolecty between pollinators and their host plants developed over tens of millions of years. Plant communities have alternately run from and chased after the edge of ice sheets since the Quaternary period began 2.5 million years ago.


A relationship tens of millions of years in the making

In evolutionary terms, the current rate of change has more in common with an asteroid impact than it does with an ice age, with no real analogue in the geologic record outside of mass extinction events trigged by volcanoes changing the climate overnight or the sudden draining of massive glacial lakes saturating once-dry landscapes – and species didn’t evolve to survive those catastrophes. Either their existing adaptations allowed them to survive, or they didn’t. Most didn’t.


Except, in this circumstance, we breached the ice dams. We hurled the rock from space. We brought the invaders over, often quite intentionally. We let the worms out of the can, cut the brakes on the trolley, pick your metaphor. Our hands aren’t clean to start with, so in this case the trolley problem has a pretty clear solution. We not only can help buffer our natural areas from the ongoing biodiversity collapse, but we have an obligation to at least try.


And not for entirely altruistic or moralistic reasons, either. We’ve all heard about the plight of the bees, the collapse of insect populations, and how that might ultimately affect our own ability to produce the food we need. Our calculus of the trolley problem changes dramatically when we find ourselves, rather than at the switch, tied to one of the tracks.

We recognize ourselves as woven into the same web as every other part of the ecosystem. But, we – including many professional and amateur naturalists – still want to insist that the web will repair itself if we just cut ourselves out of it.


About once a month, I see the famous “How Wolves Changes Rivers” viral video from 2012 making the rounds on social media (a video that has drawn criticism from the actual guy who's research informed it, by the way). The comments section quickly fills in with astonishment that restoring a keystone species had a direct impact in restoring a more representative ecology.


Who's a good boy?

I am an absolutely unabashedly broken record about this, but we’re a keystone species too. We arrived on this continent, depending which archaeologist you ask, somewhere between 10,000 and 20,000+ years ago. All of the plants and animals and fungi evolved alongside us, not separate from us. Humans were here, setting fires and harvesting wood and animals and transporting water where it would not “naturally” go that entire time.

Pulling ourselves out of the equation is just another shock on already-overstressed systems. It’s like taking our hands off the steering wheel with the cruise control still on and assuming our car will just park itself. Absolutely, we can do more harm than good when we act without thought, or without advice from the best available science, or consume more than the web can sustain.


But we can’t keep lamenting the disconnect between humans and nature out of one side of our mouths, and out the other insist that nature will heal “without us,” especially when the latter condition isn’t achievable – the worms are out of the can, after all.


If I stop going into Becker West to cut, treat, and burn multiflora rose, that ecosystem won’t suddenly start operating as if humans didn’t exist. We’re still creating noise and air pollution from the roads nearby, and night pollution from cities miles away will still affect the navigation of migratory birds and insects who might utilize the site. Anthropogenic climate change will roll on with or without on-the-ground intervention with natural communities.


I'm all for rewilding, but a passive approach simply won't work here. We can't walk away from an old pasture, where the nearest remnant prairie is miles away, and expect native seeds to find their way in. We have to take an active approach, what ecologists call translocation rewilding, introducing species that have disappeared from a site. To get there, we have to make space for them by mounting campaigns against invasive species and degradation.


Passive rewilding
Translocation rewilding

In a way, many invasive species are a symptom, and not a cause. Garlic mustard proliferates in the woodlands because in the absence of fire or thoughtful harvest, canopies fill in and create shadier conditions. Chad Graeve, Natural Resource Specialist from Pottawatamie County has more than 20 years of experience waging war with one of the most well-known invasive species. He had this to say: “For two decades we have witnessed declining garlic mustard populations in areas where we thin the woods enough to get 1,000 foot candles of light down to the herbaceous flora. The native herbaceous plants then crowd out the garlic mustard. Wherever we have not thinned the woods, garlic mustard dominates. We press on with the thinning of woods, and the application of prescribed fire every fall. The herbaceous flora continues to recover. We’re also seeing oak regeneration as a result.”


It's not that Alliaria petiolata won’t grow in full sun; greenhouse experiments show it’s equally successful in full sun or full shade. So why is it a problem in the woods and not the prairies? It’s the fact that most of our native species didn’t evolve to grow in the shade. When humans were a part of the nature web, along with bison and elk and other major tree consumers, the forests were more open, evidenced by palynology studies showing the composition of Iowa’s flora in prehistory.


Swamp milkweed appearing in a forest clearing once dominated by garlic mustard

Garlic mustard flourishes because of an unnatural condition in the woods that not many other competitors have evolved to handle. And again, we created that unnatural condition. Only in this case we created with inaction, by failing to pull the switch. We created it by abruptly halting the fires we’d set for thousands of years, by setting aside “preserves” where humans can look but not touch.


On a long enough timeline, these places will stabilize, so long as the natives who can thrive there have a way to get in. But even then, it will take a very long time, which we can see by walking through any tract of woods where 300 year old bur oaks tower over an understory of red cedar, honeysuckle, and garlic mustard.


To me, the continued advancement of most invasive species represent a symptom and not the direct cause of problems in their adopted home. They’re specifically symptomatic of the same dichotomization that got us into this mess in the first place: humans and nature are separate. They’re not. The prairies and savannas, the open woodlands, just because these have anthropogenic origins does not make them any less natural than a beaver pond.


Just two animals doing the same thing...
...creating habitat

We weed the garden, but tsk-tsk when we see a brush hog clearing an autumn olive infestation on the prairie. We mow the lawn, but wince at the idea of cutting trees to fend ofin the woodlands. We make sure the water from our tap is drinkable, but killing off invasive Eurasian watermilfoil with Imazamox so it doesn’t choke out the water lilies that actually provide habitat for macroinvertebrates? Humans don’t like to see chemicals applied to water.


Most nature lovers consider humans an invasive species. But as Invasive Species Awareness Month comes to a close, I would ask everyone reading this to consider a more nuanced stance: we’re invasive, sure, where we plow prairies and pour concrete and slaughter predators, but in those natural systems where we once had a symbiotic role, we’re rapidly approaching extirpation. And nature abhors a vacuum.


Looking Back


Junior Naturalist Camps were in full swing during the month of June. Campers visited the Big Springs trout hatchery to catch fish, tubed the Volga River, practiced archery and paddling, and learned a little campfire cookin’ at the Gateway to Adventure Camp.

The Exploring Hidden Treasures camp brought budding naturalists – including some of our summer staff along with the students – to places they’d never been including Bixby State Preserve and Backbone State Park.


The Fish Derby at Backbone State Park took place over the free fishing weekend from June 3rd-5th, where participants got to take home more than just a good meal with prizes going out to the biggest and smallest fish (my kind of derby on that last part), and the most fish, along with the opportunity to meet some aquatic critters courtesy of conservation staff.


Our volunteer appreciation dinner saw more than 20 dedicated volunteers attend to enjoy the camaraderie of like-minded conservation advocates. Our volunteers help with everything from animal exhibit security to field trips, guided tours of the mill, and stewardship projects on CCCB properties. It takes a lot of help and support to keep this ship upright, and while we can never fully express our gratitude, we hope at least some of it could be conveyed with some tasty burgers and cookout classics.


The household hazardous waste day also took place this past month, allowing folks to bring out old appliances and electronics for safe disposal. If you missed this one, keep an eye on our social media channels and website for next year’s opportunity.


Looking Forward


This July we’ve got summer in full swing and we’re here to celebrate.


On July 15th and 16th we’ll be doing our annual “trail counts” on the Pony Hollow Trail. Trail counters – volunteer and staff – will enjoy a beautiful day hanging out, talking to the passers-by about their trail dreams for northeast Iowa, and making sure our electronic trail counters are property calibrated! If you’re interested in volunteering, sign up here. Also on July 16th, at the Becker East wildlife area, the CCCB will partner with the Iowa Prairie Network for a saunter on the newly-reconstructed prairie atop the hill from county highway C9Y. Come on out and see what’s blooming, and get a little insight into how and why we partnered with the US Fish & Wildlife Service to convert the old pasture to native vegetation.



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