Columbus’ landing in 1492 had more than just a human impact. Hitching the ride on human ships were animals, insects and plants that flowed in both directions. The Age of Exuberance did not just open a new ecological reality for the Old World in its discovery of the New World—it put two worlds previously separated from one another back into a relationship with one another. The introduction of New World crops like potato, corn, cotton, squash, sweet potato, and tobacco changed European life and agriculture forever. At the same time, the introduction of invasive, Old World species to the New World changed America’s ecology, as well.

Native species are part of an established ecosystem. They have relationships with other species—predator-prey relationships, symbiotic relationships, co-existence relationships, and so forth. These relationships serve to keep the species in check, with a healthy population, without overwhelming the whole ecology. Invasive species, however, lack these relationships. They have no predators, and they have no symbiotic relationships, so when an invasive species is introduced into a new ecology, it will often overwhelm the ecosystem and choke out everything else that once grew there.

It takes thousands of years for the species of an area to co-evolve, to adapt to each other and to the peculiarities of their physical environment. This is why a plant species which has survived in the area for a few decades or even a couple of centuries isn’t considered to be native. …

Can an immigrant plant ever become native—in the biological sense? Yes, after thousands of years. No one can give a precise time, for the moment a plant enters new territory, the forces of evolution begin: any time the new environment (including, remember, animals and other plants) favors one genetic trait of the newcomer over another, natural selection begins. I would expect that after even just a few hundred years, some species (particularly insects and other invertebrates with short life-cycles) would adapt to the presence of a newcomer, for a food-source (i.e. any other organism) will not go forever unused.¹

Of course, the biological exchange of the Old and New Worlds was not even that simple. Take, for instance, the case of the horse. The horse actually evolved in the Americas, and migrated across the Bering land bridge into Eurasia. Once the land bridge was closed again, the extinction of the megafauna in North America led to the extinction of the horse in its native ecology, but on the plains of Eurasia, where the horse was invasive, it thrived. The horse was domesticated by agricultural civilizations, who then unwittingly returned it to the New World after 1492.

The Spaniards attempted to settle in what is now Argentina in the early 1500s, but failed. They did, however, leave behind some horses. When they returned to try colonization again in the 1580s, they found horses in abundance. A traveler at the turn of the seventeenth century reported horses “in such numbers that they cover the face of the earth and when they cross the road, it is necessary for travelers to wait and let them pass, for a whole day or more, so as not to let them carry the tame stock with them.” In 1744, a Jesuit priest in the pampas reported herds of feral horses so numerous that it would take three hours for them to pass by “at full speed.” (Manning, 2005)

What Europeans found instead on the plains of North America was buffalo—in positively massive numbers. But these buffalo were not native to North America. They had come from Eurasia, and crossed the land bridge into the Americas while the horses were migrating from the Americas into Eurasia. Behind the buffalo came another invasive species: Homo sapiens.

While the “overkill” theory has been vastly overstated, it’s also undeniably true that the introduction of a new, invasive species of alpha predator tipped many species over the edge—possibly including the horse.

The survival—and flourishing—of the buffalo is telling. Humans and buffalo already had a relationship before entering the New World, and once they came into it, while humans may have had a fairly negative impact on those species they did not yet have a relationship with, their relationship with the buffalo enriched both species.

After tens of thousands of years and multiple waves of migration across Beringia (and possibly even from Europe), the human population in the New World became native. The process was difficult and many species that were already ailing were tipped into extinction, but ultimately, this invasive species became native. Culture allowed humans to enter into relationships with other species far more quickly than genetic evolution alone would have allowed. American Indians are in every meaningful sense “native”—they have a relationship with the ecology, or to put it more strongly, they are part of that ecology.

Perhaps therein lies the most important divide. Native species belong to an ecosystem; invasive species are passing through it. The process of becoming native is a process of finding a place in an ecosystem—a process that cannot help but change the ecosystem as a whole, and everything in it, at the same time. By the time the next wave of invasive humans arrived at the shores of Turtle Island, American Indians had turned the continent into a thriving horticultural paradise, bursting with a biodiversity and ecological wealth that boggled the minds of Europeans so used to squalor, scarcity and deprevation as the natural order of the world. Yet the wave of invasive species the Europeans brought with them undermined the very richness they came to exploit, and with the loss of the ecologies that native peoples had become part of, their very existence was itself threatened. Writing about New Zealand, another “neo-europe,” or colonial area of roughly similar ecological conditions to Europe and thus ripe for European exploitation, Crosby writes:

In the 1850s, with the avalanche of the pakeha and associated species pouring ashore, more models of Maori extinction appeared. Exotic weeds ran like quicksilver among the roads into the bush. Native birds retreated as exotic cats, dogs, and rats advanced. The inadvertently imported Old World housefly proved to be so effective at driving back the native bluebottle fly, hated by the pakeha because it learned to lay eggs in the flesh of sheep, the herdsmen took up the practice of carrying their own flies along with them into the back country in jars. The brown rats swept through the South Island, again exterminating all but a trace of the Maori rats, and in the 1860s were deep into the Southern Alps and growing to enormous sizes. Julis von Haast, a geologist who arrived in New Zealand in 1858, wrote Darwin that there was a proverb among the Maori that “as the white man’s fly drives away our own, and the clover kills our fern, so will the Maoris disappear before the white man himself.” (Crosby, 1993)

Ultimately, what the Europeans brought with them was in large part a whole invasive ecosystem.

The members of the portmanteau biota had at least the same advantage as had the first humans and their associated organisms that crossed into the New World from Eurasia: the advantage of moving into virgin territory and, with luck, leaving a lot of enemies behind. Back in the Old World, most particularly in the densely populated areas of civilization, many organisms had taken advantage of contiguity with humans and their plants and animals to become their parasites and pathogens. These freeloaders often were slower to emigrate to the Neo-Europes than were humans and the organisms that humans intentionally brought with them. For example, Europeans brought wheat to North America and created the first of their several wheat belts in the Delaware River valley in the eighteenth century where the plant thrived in the absence of its enemies. Then its old nemesis, the Hessian fly, unjustly blamed on George III’s mercenaries, who supposedly brought it across the Atlantic in their straw bedding, arrived and obliged farmers of the valley to find a new staple. (Crosby, 1993)

The process of becoming native began almost immediately for these plants. As Toby Hemenway writes:

As one illustration, the author describes the native-plant campaigns of Hitler’s followers, though he is very careful not to call exotics-haters Nazis. He believes invasion biology is rooted in the same fears and prejudices that power Nazism and other racist, genocidal ideologies. A desire for genetic purity and preservation of the homeland, dissatisfaction with current status, an easily identified enemy, and a simplistic answer—extermination—are elements that these ideologies share. And he does call invasion biology an ideology, demonstrating that it cannot justifiably be called a science. In no scientific discipline can data be suppressed or used selectively to support a preconception as is done in invasion biology. Pseudoscience is known for refusing to acknowledge conflicting data, not testing assumptions, exaggeration of limited truths, and circular arguments. (”If it’s not native it’s bad, and the reason it’s bad is because it’s non-native.”) Invasion biology fits this pattern.

We greatly prefer to find simple, physical causes for problems and then eradicate them. We’re very good at spotting and killing enemies, and we feel virtuous while we do it. We’re far less successful and confident when causes are multiple, the solution requires changes in our thinking, and the “enemy” is our own behavior.

Most harm resulting from introduction of non-native species should be blamed not on the species themselves, but on human destruction of habitat and on practices that change landscapes so they no longer support their native vegetation. Non-native species are almost never capable of competing successfully with species in an intact native ecosystem. (The author points out one oft-heard contradiction here: that exotics often drive out the better-adapted natives. Say, what?) Clearing, soil disturbance, creation of sunlit edges, harvesting, and the other collateral damage of development all degrade native habitat to render non-natives more suited to the new conditions. Thus yanking the exotics will do no good—they’ll come back faster than the now-handicapped natives under the changed conditions.

Another harmful manifestation of exotic-species hatred is our hubris: the conviction that we know better than nature which organisms should be living somewhere. Eradication of non-natives has often had a Vietnam-village effect of destroying what we are trying to save, and can in fact damage ecosystem function more than the exotics. Evidence is mounting that the vigorously growing blends of native and non-native plants that “invade” damaged land are yet another example of nature’s wisdom and resourcefulness. Nature creatively mingles both native and exotic without prejudice, using all resources available to throw a green Band-Aid over ravaged landscapes. We demean her intelligence and set back the healing process when we hack away these recombinant communities. The book’s final section uses this view as the basis for a new relationship with human-dispersed species.²

And what of the people? While previous waves of migration into the New World used culture to become native more quickly, we have so far used our culture to try to remain invasive. We do not want a relationship with our ecology, even as the species we brought with us are re-negotiating the terms of their newly mutual co-existence. We continue to shape our attitudes and convictions based on the customs of England and the sensibilities of the Old World. We have used our culture to resist change and adaptation, and to slow the process of becoming native. We remain an invasive species in the New World, because we refuse to become native. We do not want a relationship with this New World; we want to rule over it.

What then, in essence, is it to be native? To describe a person as a native is not only to say of them that they were born in a particular place - since this after all can be said of everyone - but that they belong to that place, that they are made of its matter and imbued with its distinctive character. To be native is to have one’s identity shaped by the place to which one belongs: one is a creature of its topography, its colours and textures, saps and juices, its moods, its ghosts and stories. As a native, one has one’s taproot deep in a particular soil: one has grown in that soil, and continues to be informed and sustained by its essence. One is kin to all the other beings who arise out of and return to that patch of earth, and one draws one’s substance and one’s templates for meaning from it. The native is thus one born into a world which prefigures, predetermines, her being in every detail. She grows into the space that has been prepared for her, as a chick grows into its shell. She respects that space, never jeopardizing the perfect fit between herself and her world by taking radical initatives or assuming hard-to-accommodate shapes of her own. The world as it is given affords material sufficiency, mythic inexhaustability and a rich vocabulary for both pragmatic and imaginative purposes.³

Works Cited

Crosby, A.W. (1993). Ecological Imperialism: The Biological Expansion of Europe, 900-1900. Cambridge: Cambridge University Press.

Manning, R. (2005). Against the Grain: How Agriculture Has Hijacked Civilization. New York: North Point Press.