Invasive Species

“War is being waged all across the country against the invasive plant and animal species — some 50,000 of them — now spreading across the U.S.”

To move to Hawaii was to transplant ourselves into an entirely new biome. Just as we were easing into the familiarities of the Virginia forest, the birches, pines, and tulip poplars, we jolted ourselves into an alien world. The white apple flowers and crimson blueberry leaves are gone, replaced by top-heavy papaya trees and enormously floppy banana trees.

Even the familiar species take unfamiliar shapes. The petite, fragile Thai basil of our Virginia garden is a perennial, woody bush in our Hawaii garden. The impressive 8-foot Virginia tithonia are veritable trees here, 15 feet tall or more. Grass isn’t just grass here. It’s 12 feet tall, in clumps thicker than tree trunks (and harder to cut down). Our first time stepping on this land, we were ten feet from a broken down flatbed truck before we noticed it, its bulk having been entirely swallowed by the grass. I found seedlings growing out of the laces of my boots yesterday.

There are the iconic Hawaiian plants, its showy hibiscus flowers and fragrant puakenikeni and plumeria. And there are the plants that tell you you’re in the tropics, the coconut palms and bananas. But this being the tropics, a dizzying diversity of unknown species greets us every time we venture into the forest. A temperate forest is usually dominated by fewer than ten tree species, whereas a tropical forest can have hundreds of tree species coexisting in a single acre.

But this isn’t just “the tropics”. It’s the most isolated land on Earth. None of the species listed above have been here for more than a few hundred years. The grasses were brought by the ranchers and the flowers as ornamentals less than 200 years ago. Coconuts and bananas were brought by Polynesian settlers a thousand years ago.

“Invasive species” have gone mainstream. Anyone even tangentially involved in agriculture or land restoration seems to have strong opinions about “native vs. invasive” species. Ask them about this tree or that shrub, and they’ll usually attach its origins to their description. “Native tree, the native birds love the berries” or “That thing’s invasive, pushing out the native groundcover.”

To the native-anxious, Hawaii is the nightmarish microcosm of what’s in store for the rest of Earth. Hawaii’s surviving native ecosystems have been pushed to marginal land high up the volcanic slopes. Talking to local farmers, you sense that you’re embroiled in an epic struggle to hold back the invasion. The species I’ve learned quickest are those that everyone loves to hate, the ones that neighbors suggest not-so-subtly that we need to remove for everyone’s sake. The African tulip tree, the fiddlewood tree, the guava, and the gunpowder tree. The guinea grass and the shy grass.

Even folks who condemn hateful rhetoric against immigrants will advocate for the violent removal of “invasive species” in favor of “natives”. The mission of the Big Island Invasive Species Committee is “to prevent, detect, and control the establishment and spread of invasive species threats to our environment, economy, and way of life. We work to protect… our communities from new and ongoing threats,” language that could have been lifted from a Trump speech.

When we kill the little fire ants living around our home, we justify it with a casual aside, “they’re not native”. Nations engage in coordinated efforts of extermination, (e.g. New Zealand killing millions of possums every year), judging a being’s right to live based on how many generations its ancestors have lived nearby.

To be considered invasive, a species must have been introduced by human action and “cause harm to the environment, economy, or human health,” a distinction so broad that nearly everything could be considered invasive. In the postlapsarian age, human action is held accountable for the ebb and flow of species across all ecosystems. And if “the environment” is held to be the prelapsarian environment, the mere existence of a non-native pretells that it is consuming nutrients and habitat that could have been housing a more purely native life form. In common parlance, “invasive” turns into just a fancier sounding word for “weed”.

While my cosmopolitan sensitivities balk at the thought of destroying life that isn’t “native enough”, my rural proclivities are more understanding. Trying to grow food forces you to accept that favoring one life over another is an inseparable part of being alive. There are good reasons to prefer natives as a rule of thumb. Established native species have a track record of success in a given climate and matrix of species interactions. A native ecosystem can feel more stable, like it’s been around forever and can continue forever into the future. An ecosystem disrupted by an outsider can feel precarious, in a state of constant flux.

On the other hand, seeking stability in nature is a fool’s errand, the search for ecological equilibrium a quixotic one, “nature in balance” a misunderstanding. Instead, nature could be conceived as a small boat rocking on the ocean, as a series of responses to disruptions. The boat may continually trend toward an even-keel, but such a balance is not long to be had, whether the knock comes from a volcano, a nuclear meltdown, or an aggressive newcomer.

On the other, other hand, take this long-view conception to the extreme, and soon you’ll be excusing any and all actions, abstracting the Deepwater Horizon oil spill away as nothing more than another “wave” that will momentarily “knock the boat” off-keel. 

The truth is somewhere in between. Nature is neither timeless nor infinitely recoverable. Beyond a tipping point, the boat could capsize altogether. We all depend on that boat staying upright.

Ostensibly, we fight invasives to support a “healthy ecosystem”. How is the healthiness of an ecosystem judged? In its ability to deliver on some human need? On its stability? Stability measured by what metric? Dig deeper, and you’ll often find superficial and circular reasoning. We point to masses of kudzu covering trees as an unhealthy ecosystem, one species dominating the landscape. We point to redwood groves, with one species dominating the landscape, as a healthy ecosystem.

Speaking of kudzu, this vine native to East Asia is probably the most infamous invasive in North America. In the Southeast especially, images of trees devoured by a blanket of vines haunt the imagination. People who couldn’t name 10 plants can point out kudzu.

Yet the demise of the forest hasn’t happened. A sampling found that kudzu occupied just 0.1% of the South’s forests. Like many plants labeled as invasive, kudzu thrives best in areas disturbed by human action — places like roadsides and railroad embankments, cuts in the forest with full access to sunlight, where native species have already been excavated away, . (The Soil Conservation Service incentived kudzu planting to combat soil erosion in the 1930s.) Funny enough, most of what people experience of the forest is seen from the inside of a car. After riding through miles of highway flanked by kudzu on all sides, it’s easy to imagine an unstoppable invasion of the vine.

So many of the species we tend to think of as weedy or invasive are those pioneer species — fast-growing, tons of seeds, readily colonizing bare ground. They return stability to the soil and hold onto fast-eroding nutrients after a disturbance. They occupy that specific niche. They’re not often seen in what we think of as “natural”, undisturbed ecologies. Because our landscaping and agriculture require us to disturb the land, we are readily annoyed by these pioneer species that seem to grow better than what we want to be growing — the corn, the wheat, the flower beds.

As such, invasives rarely take over undisturbed native ecosystems. They need the wide rocking of the boat to gain a foothold. Invasive species are more often lagging indicators, not the cause of a suffering ecosystem.

If our goal is to rid the land of weedy pioneers, we could just sit around and wait. They will eventually create the conditions for their own demise. Once they’ve stabilized the system, they’ll be replaced by plants more suited to the less disturbed ecology. 

The problem for us there is twofold. One, this process could take longer than a human lifespan (cue John Maynard Keynes “In the long run, we’re all dead”). Two, the global human population is fully dependent on disturbing land to create the conditions for our annual food crops (which, unsurprisingly, are also weedy pioneer species).

And sometimes, introduced species can be major disruptors. In 1900, chestnut was a dominant species of the Eastern forests. In 1904, a fungus from Asia hitched a ride on a Japanese chestnut imported into the U.S. Less than forty years later, nearly every mature chestnut in the East was dead, almost four billion trees. And like smallpox in the post-Columbian Americas and Bubonic Plague in medieval Europe, we are directly susceptible to invasives, ourselves.

All this leaves me muddled. Introduced species can wreak havoc. But there are real problems with our approach. Too often, nativist rhetoric is used as a quick justification for controlling life under the guise of caring for it. Couched in the language of defense, we engage in offensive pursuits against species we have found guilty. “Invasive” — we claim to protect the environment from invasion to obscure the uncomfortable truth that to live means to prefer some over others, and that preference means life for some, death for most.

And yet, knowing all this, the majority of my time in our three months in Hawaii has been spent cutting down invasives. The fiddlewoods sneaking up the hedge. The blooming African Tulips. The massive gunpowders. The clumping 12-foot tall spiky guinea grass. The little fire ants. Fencing out the wild pigs. I have bought into the fear, into the mindset of needing to defend this land against the horde of invaders. I’m on alert at all times, spotting the nondescript fiddlewood leaves poking through the foliage as if they were painted neon orange, relieved when the tree is still small enough to pull up. I shock myself at how quickly I’ve shifted from hesitation to vengeful attack. I contemplate buying herbicide to paint on the stumps of the trees I cut down to prevent regrowth, each stump sprouting four new trunks. We spread pesticides to control the little fire ants that pour into the house.

Though late to the globalization game, Hawaii is ground zero when it comes to invasive species. Millions of years of isolation enabled the evolution of highly unusual native flora and fauna, 10,000 species found nowhere else. And now, a couple of centuries of exposure to globalized trade and industry has given Hawaii its moniker of “extinction capital of the world.” None of the animals or plants I come across daily — zero — were on the islands a couple thousand years ago. 

The phrase “novel ecosystem” — systems heavily influenced by humans but not directly under human management — was invented for places like Hawaii. It’s not enough to stick to the “native > invasive” rule of thumb here. Hawaiian landscapes are a jumble of species from around the world duking it out. New species accidentally arrive via ship or plane every two weeks, it seems. Still, efforts abound to reintroduce native species around the island. Their native habitat is so far gone that intensive human intervention is required to continually clear out new habitat. Which brings up the question, what’s the point, again?

And yet, I also seek out native plants. I collect their seeds and cuttings when I spot them and go out of my way to section off space for them, though they don’t produce food, flowers, or any other obvious “service”. 

I do it for the novelty of Hawaii’s strange endemic species. I do it because I am a story-telling animal, one who finds meaning fitting into historical contexts. There may be other species more suited to the novel ecosystems of 2022, but there is something intrinsically Hawaiian feeling about the ‘ohi’a and the koa and the sandalwood; the ‘ohi’a: the first tree to recolonize lava fields, taking many possible forms depending on its habitat (species name: polymorpha), its mature height ranging from a few shrubby feet tall to 80-foot tall trees; the koa: young trees have many small leaflets while older trees have completely different sickle-shaped leaves. These endemic trees define what is unique about Hawaii just as our family icons define our heritage and our memorials define our country. I can feel the bark of the trees and know that the first humans on the islands over a thousand years ago may have stood in a similar place and felt a similar tree. Planting an ‘ohi’a, I feel closer to the identity of the place. There is a wisdom within the trees and animals who have known these islands for so long, and that can’t always be captured in rational words.

The Big Island Invasive Species Committee does important work. In 2009, a few deer were illegally introduced to the island. Anyone who has tried to grow something in the presence of deer knows how much of a pest they are. Building a short fence against wild pigs is one thing. Deer require 8-foot tall fences, at least. Deer have had a profound effect on Maui and Molokai. Without predators, they strip landscapes bare of vegetation. When the heavy rains come, there’s nothing left to hold the soil in. The land runs off into the oceans, killing reefs and fish. The ecosystems would eventually rock back toward equilibrium as deer-resistant trees and groundcover start to take hold and maybe the human population could abandon agriculture and eat deer instead. 

Or, if you’re the Big Island, you could aggressively pursue and kill the few deer before they reproduce. And that’s what the Committee did, announcing the Big Island as officially free of deer in 2017, to the great relief of everyone.

I try to fence out the wild pigs before they dig deep furrows throughout the fields. I try to cut down the African tulip trees before they spew their tiny seeds, hundreds per seed pod. I try to tear out the fiddlewoods from the (also non-native) hedge. The trees I cut are abundant, fast-growing, and spread easily.

This land is recovering from decades of the major disruptions that modern agriculture requires. Its recovery could take many paths. If untouched, within a few years it would be dominated by thickets of guava and cane grass with gunpowder, African tulip, and albizia trees forming an unstable overstory, adding chaos when their fast-growing softwood topples over in tropical storms. Pigs would run rampant, clearing out paths through the dense understory, digging trenches out where standing water would breed swarms of mosquitoes. 

There’s nothing wrong, per se, with this outcome. We like to bemoan that these are non-native species, but what we strive to replace them with — the lychee trees, the cows and goats, the bananas and avocados, the lawn grass — those aren’t native either. The thicket of “invasives” just doesn’t match our senses for what a landscape should look like, nor is it very hospitable to our species, nor does it provide easily accessible food for us. 

I’m not philanthropically trying to return the land to its two-thousand-years-ago state for its own sake. I am explicitly trying to shape the ecosystem to fit my vision, not all that different from a strip-mall developer. Not all that different from every life form, in fact. Reshaping your surroundings is a fundamental characteristic of all life. Some do it cooperatively, others parasitically.

I haven’t yet addressed the elephant in the essay — the most disruptive, aggressive, invasive species of all is Homo sapiens. Though rarely spoken out loud, it is impossible to separate this inconvenient fact from the general discourse on non-natives. To remain dogmatic about native species is to disavow any role outsiders may have in an ecosystem; is to condemn Homo sapiens to only ever detract from an ecosystem; with implications that have us fleeing to Mars as a “solution” to our predetermined ecological destruction.

And among Homo sapiens, is there anyone more invasive than someone many times removed from where their ancestors could be called indigenous? Who have invaded an isolated tropical land, an ocean and a continent away from their birthplace? In short, surely I sympathize with those species known as “invasive” because I, myself, am invasive. 

Invasive vs. native. This dichotomy hides the wide spectrum of a species’ place in an ecosystem. Hawaii refers to “canoe plants” to describe the handful of useful species that Polynesians carried to the islands via canoe. There’s “naturalized”, technically a superset of “invasive”, colloquially a warily-accepted-into-the-family non-native. Like daffodils. In short, not every non-native is labeled as “invasive”. Non-natives can be introduced into an ecosystem and play a cooperative role.

Wherever you live, non-native species are there to stay, humans included. The global movement of people and goods has flattened geographic barriers between species, as if the snow globe of Earth’s species were rocked side to side. Efforts at total eradication require absolute warfare, if they’re possible at all. In an ironic twist, to return and maintain ecosystems to their prelapsarian state would require practices that are every bit as dominating and destructive as paving over forests with subdivisions and lawns. 

The Hawaii Pacific Weed Risk Assessment scores a species’ “risk of becoming invasive” in Hawaii on a 49-point scale with questions like:

• Are humans likely to disperse the plant?
• Is the plant a weed elsewhere in the world?
• Is it shade tolerant?
• Does it produce a lot of fertile seeds that are easily dispersed and remain viable for years?

From these criteria, we can see that the invasive distinction boils down to “How difficult is it for humans to control? Does it get in the way of other human objectives?”

Life is unpredictable, dynamic. To control life, to keep an ecosystem static, to what we project it “ought to be”, you must cage it, exterminate it, remove the very essence of life from the body.

In cooler climates, control seems achievable. In the tropics, control feels futile. Everything is just too fecund. Any attempt at mainland-style control takes parking lots full of heavy machinery and a refinery’s worth of diesel.

In the end, the dichotomy between native and invasive is another broad-brush attempt to simplify the moral question of how to be a good neighbor. No matter how dogmatically we defer to some objective standard of nature, whether that be nature-before-man, nature-without-man, or nature-as-an-object-for-the-free-market, we can’t escape the underlying truth – that there is no easy one-size-fits-all answer; that we cannot absolve responsibility for our actions under single-phrase principles like “natives > invasives”; that we are conscious creatures and that our choices matter, including “do nothing”; that we are a part of our ecosystem; and that the parable of the invasive species can guide us to pursue non-invasive behaviors in ourselves.

When non-human animals are killed simply because they ‘don’t belong’ and not because they are clearly causing some measurable harm, we have decided that erasing the taint of the human is more important than the lives of animals (who, lest we forget, have no conception that they are in the ‘wrong’ place).

Emma Marris