Few manmade barriers rival the Great Wall of China in scope, ambition or sheer mythical presence. So large does the wall loom in the public consciousness that it is often claimed to be visible from space, though in fact it is not. The assertion feels plausible, even intuitive, because of the sheer scale involved: a wall crossing mountains and valleys and desolate uplands. The mind boggles at such an achievement. 

And yet, it is not alone. In Australia, thousands of miles to the south, there is an equally impressive display of human ingenuity, if not of equal technical mastery. What it lacks in sophistication is more than made up for in extent, however. The Great Wall never fully walled China, but the enormous Dingo Fence guards a full quarter of a continent, running nearly from coast to coast, unbroken through some of the most inhospitable landscapes in the world. Warding off the Australian southeast, this fence begins between the towns of Jandowae and Jimbour in southern Queensland and runs for a total of almost 3,500 miles before it ends off the Eyre Peninsula on the cliffs above the Great Australian Bight. 

Remarkably, the longest fence in the world was built and is maintained for a single purpose: to protect Australia’s pastoral heartlands from the depredations of a canine. The dingo, the southern continent’s famed (or infamous) wild dog, is a complicated, emotion-stirring animal. A reddish, medium-sized canine with short, smooth fur and a powerful bite, it is the largest predator in the Australian Outback and the only one dangerous to sheep and other livestock. On rare occasions, they have even been known to attack humans. 

Dingos are referenced variously as a valuable native of the Outback, an invasive species or sometimes little more than a breed of feral dog. Government policy simultaneously lists the dingo as “native wildlife” under the Nature Conservation Act of 1992 and a “restricted invasive animal” under the Biosecurity Act of 2014. The situation, then, is quite hopelessly confused, and a bemused onlooker might reasonably ask: Why? 

Of all the continents in the world (except Antarctica), Australia is the most ecologically isolated. For 35 million years, it has drifted in the South Seas completely severed from all other landmasses and from nearly all contact with their species. Besides the inevitable bats and seals that swarm the skies and shores of practically every landmass, the only group of mammals ever to reach the continent were a few lineages of small rodents. The result was a fauna both weird and wonderful: giant reptiles, flightless birds and a near-total lack of live-birthing, placental mammals. Until, that is, a certain hairless primate waded ashore about 50,000 years ago.

The tally of casualties that unfolded over the ensuing millennia was immense. Every single large, terrestrial predator on the continent was wiped out save one: a striped, dog-like marsupial called the thylacine. Alone among Australia’s major carnivores, this species hung on, enduring across the mainland and New Guinea until only around 3,500 years ago. 

By then, a sea-faring people, the Austronesians, had embarked on their great expansion down through Oceania. It was most likely this culture that brought a certain lineage of primitive dogs who would finally wipe out the thylacine everywhere except Tasmania. The descendants of those ancient dogs would go on to solidify their place on the continent such that by the colonial era, the dingo was the sole apex predator across the Australian Outback.

For as long as ecologists and biogeographers have been aware of this complicated history, they have been unsure what to make of it. The ancestors of the dingo may have wiped out the thylacine on the mainland, but they also replaced it; what would remain should they too vanish is an ecological vacuum. 

Whatever their niche and influence, what’s generally accepted is that the dogs are the descendants of an ancient domestic introduction, which usually earns a species the label “feral”: not truly wild. Peter Menkhorst and Frank Knight’s generally excellent “Field Guide to Mammals of Australia” treats the dingo as a run-of-the-mill non-native species, squeezing it between the entries for invasive cats and foxes and withholding any legitimating conservation status. This is highly relevant, as such a status — “least concerned,” “vulnerable” or “endangered” on the International Union for Conservation of Nature’s Red List — is only accorded “genuine” species, and the absence of an animal from the Red List is therefore tantamount to a rejection of its independent value. A 2019 IUCN workshop decided to classify the dingo as a “feral domestic” and therefore not a “real” species in its own right. 

The case of the dingo, then, strikes at the very heart of the ecological conundrum of ecosystem change — of what it means to belong somewhere in nature. Fundamentally, the dingo forces us to question the coherence of “nativeness” as a meaningful concept. 

The Green Earth Tilts

What does it mean for a species to be native or not? The seeds of this notion extend far back into history.

Grand ecological changes — being slow, laborious processes — are almost always beyond the observational purview of a few generations. Even where certain forms of recollection hark back much further — as with some Aboriginal tribes that seem, remarkably, to preserve memories of ancient, post-glacial floodings — the broader elements of nature tend to be regarded essentially as brute facts: what is, is. 

In lieu of any cultural understanding of deep time, geological history or evolution, to suppose the essential fixity of nature was once perfectly reasonable in light of the available evidence. In the Western tradition, early Greek philosophy would eventually solidify such primordial presumptions of nature’s fixedness as part of an intricate, more robust cosmological system. The notion of the Great Chain of Being posited a vast sequence of all created things arranged in respect to their descending degrees of perfection. For reasons related to certain intricacies of Aristotelian metaphysics, the Great Chain was necessarily unalterable and the particulars of the natural order therefore made an absolute.

This philosophical outlook did unquestionably bring a great number of benefits, the dividends of which we continue to enjoy. The notion of the fixity of nature, of its fundamental coherence and rationality, as inherited from the ancients and refined by the Medieval scholastics, was foundational for the establishment of modern science. Equipped with this faith in the intelligibility and continuity of the created order, the early naturalists set out to explore and catalog every reach of a world ripe for classification. Much knowledge was reaped in this process, but even fertile fields can bring up weeds.

The first explorers did not operate within our modern ecological definitions of nativeness and non-nativeness, but circumstances eventually forced them to adapt. The word “native,” deriving from the Latin root nātus or “birth,” originally denoted that which was simply natural or unmodified, uncultivated, undomesticated. In other words: wasteland. 

It was not always clear to the naturalists whether a given species had originated in the region where it had been documented or whether it might have been brought there by artifice, perhaps even by the very explorers logging the observation. A practice developed of appending an asterisk (*) to signify the listing’s doubtfulness. 

More and more elaborate practices emerged to keep track of the “validity” of such observations, and the initial asterisk gave way to complex definitions and categorizations. Herein lay the germ of the entire modern concept of nativeness: the idea that certain observations documented nature as it should be — in its divinely ordained state — whereas others marked deviations. In any given location, some species belonged and others did not. 

Eventually, as the subfield of ecology developed to study the dynamics of ecosystems at the landscape scale, the practice of dividing the world into definite species was expanded to the level of ecological communities as well. In his landmark book “Chance and Change: Ecology for Conservationists” (1998), William H. Drury described how many observers “think of the landscape, vegetation and other organisms as an entity that exists over time and takes on its own identity.” 

All of this matters greatly, for if species exist as totally discrete entities arranged in an absolute, preordained pattern, and if the ecological communities they exist within likewise consist of static systems, then no room whatsoever is left for the movement of populations, nor for the establishment of new arrivals. It would mean that nature is essentially set, and any change from the original baseline (whatever that may be) would only ever be deleterious. This general conception, this hunch that there is a specific way nature ought to be and from which our actions cause it to deviate, has persisted long after the abandonment of the Great Chain of Being and the cosmology it entails. 

The modern view of ecological communities as static, perpetually self-maintaining systems is directly traceable back to that idea: Nature is fundamentally unalterable if it is to remain known as “nature” at all. To be “native” is to occupy one’s proper place in a grand, unalterable pattern, and those populations that do not conform — say, a certain breed of wild dogs in the Outback of Australia — therefore have no claim to ecological authenticity or, it follows, protection.

There are countless other cases like the dingo: vagrants, castaways and loiterers far outside their “proper” homelands. Some may be detectable from their deleterious ecological impacts — invasives in the proper sense — but a legion of others are more difficult to separate from the landscapes they now exist in.

Indeed, biologists even introduced the term “archaeophyte” to denote a plant introduced so far in the ancient past that its status as non-native has been totally eclipsed by eons of time. Examples abound, including such hallmarks of the English countryside as corncockle, mugwort and even the emblematic field poppy. No equivalent term exists for animals, but there are many of them as well: the dingo, of course, but also rabbits in England, red deer in Ireland, mouflons (wild sheep) in Cyprus, cuscuses (a kind of marsupial) in insular Melanesia. All of these were introduced millennia ago — in the case of the cuscuses, apparently before 20,000 B.C.E. The Cyprus mouflon is recognized as its own subspecies, Ovis orientalis ophion, despite being the descendant of ancient domestic sheep. It is notable that this exact same origin disqualified the dingo from serious recognition.

Indeed, the claim has been made that the dingo, whatever its origins, is now a fully wild animal, enmeshed in its ecosystem — and it cannot, therefore, be equated with domestic livestock or be condemned as a mere escaped dog. So the argument goes. This, however, is exactly the difficulty: The status “feral” almost by definition means it cannot be outgrown. Wildness and domesticity constitute a sharp, ontological binary, and the state of “feral-ness” is a catch-all label for any member of the latter group caught attempting to escape — quite hopelessly — the original sin of human companionship. The Midas touch of our species, whose brush invariably transmutes nature into artifice, can take lineages out of the wild, but it cannot put them back. Once a domestic, always a domestic. There is no requiem for the stray dog.

The problem deepens very quickly: Beyond the cases of assisted movements, recent or ancient, there is also the number of apparently un-assisted, purely “natural” migrations that have occurred in historic times. When human pressures caused the populations of New Zealand fairy penguins, Eudyptula minor, to decline during the colonial era, its Australian relative, E. novaehollandiae, took over the region around Otago. Today, both species coexist in different parts of South Island. The question presents itself: Which is the “valid” population? Are the interloping Australians obstructing their “more native” cousins from retaking their former range, or does their unassisted arrival validate their presence? 

Similarly, consider the cattle egret, which has been rapidly spreading across the Americas since arriving from the Old World around the 1870s, seemingly by its own volition yet in response to favorable conditions created by humans. Is that a natural or artificial migration? 

Such populations are at times termed “neo-native” to acknowledge the inherent dynamism of species ranges, yet the difficulty does not end there, for such unassisted-yet-facilitated movements are not merely a feature of the present and future but of the past as well. Even so archetypal an animal as the moose, an icon of Canada and the great northwest, appears to have only arrived in North America at the end of the last ice age, entering an ecological vacuum created when early humans wiped out the related “stag-moose,” Cervalces scotti. 

To be forced to conclude that the moose, of all animals, is in some sense non-native to Canada and Alaska seems almost a perfect reductio ad absurdum of the entire concept of stringent indigeneity. Nativity and non-nativity are ultimately concepts circumscribed by human definitions, while the difference between non– and neo-nativity is a judgment entirely divorced from actual ecological impacts. On a tilting, moving planet of porous boundaries, things change, species shift and our definitions, surely, must be able to accommodate this reality. All the same, to completely reject the categories of nativeness and non-nativity seems perilously close to an invitation to ecological anarchy. Perhaps there is another way.

Order In A Shifting World

As Drury wrote, referencing the thought of Aristotle: “If one starts with false premises, dialogue and logic will not necessarily lead one to the right conclusions.” Disturbance and disruption, viewed through the lens of an essentially fixed, inflexible natural world, are scarcely distinguishable from “damage.” If the cause of such disruption is a native species, it must be overpopulated and therefore eligible for “control.” If the cause is a foreign arrival, its impact is the clinching proof of its malignancy. 

Rarely asked is whether chaos and dynamism might actually have a place in the aboriginal state of an ecosystem. Might the recent, historically observed inertness itself be the anomaly, brought about by the neutering of wild potencies? And most importantly, does the political and conservation discourse regarding “natives” and “invasives” adequately distinguish between concerns that are fundamentally aesthetic versus those that are ecological? 

Consider the dingo: Whether it is the descendant of an ancient wild canine or a partially domesticated offshoot thereof, is, from an ecosystem perspective, utterly irrelevant. Whether the ancestors of the dingo went straight from the teak and laurel forests of Asia to the eucalyptus woods of Australia, or whether they spent some interim period loitering about the edges of human camps, has not the slightest bearing on its current, measurable ecological impact. Nor, in either case, does it render the dingo, as a canid on a formerly canid-less continent, the least bit more or less foreign to its broader environment. 

The sole place the classification of the dingo matters — yet here it matters immensely — is in the minds of Australian government officials and the conservationists they consult. For them, the matter at stake is nothing less than whether to regard the animal as a genuine, valid species with its own, intrinsic value — or as a mere stray dog, not even a real species in its own right. 

Drury responded to the great variance and mutability of nature, and the lack of workable definitions in his day, by rejecting the fundamental meaningfulness of “ecological communities” as a concept: Communities, he concluded, are merely interpretive frames we impose upon the clutter of the natural world as aids for communication and understanding. In this, he is essentially a sort of “ecological conceptualist.” This would, indeed, resolve the questions, if not the actual practical issues, surrounding nativeness in species: Nothing is really native, for there are ultimately no real communities to be native to.

Perhaps we need not go quite so far. As discrete assemblages of particular species, communities are not entirely self-organizing or enduring, as Drury rightly notes. Those assemblages of organisms that we chance to find associated with each other in nature are frequently the result of a great deal of happenstance and contingency. Should one take a time machine 3,000 years into the future or the past, the composition of trees in a given forest would likely look very different. 

There is, however, a difference between communities and ecosystems. The validity of the latter as genuine natural phenomena seems salvageable if conceived of correctly.   

The concept of the functional trait is useful here. Per one definition, a functional trait is “a well-defined, measurable property of organisms, usually measured at the individual level and used comparatively across species,” which, per a second definition, may be “morphological, biochemical, physiological, structural, phenological or behavioural characteristics … that influence performance or fitness.” 

Traits determine the influence of the trait-holders on their environment, as well as their varying abilities to respond to it. Examples might include anything from plants’ seed dispersal capacity, palatability, growth rates, size and so on. In animals, they modulate grazing, hunting and all other forms of behavior. Recent science has shown that functional diversity and differences in key traits between introduced and recipient plant communities provide the best descriptor of invasive plant success. Even more significantly, a 2024 paper demonstrated that it was traits, and not (pre)historical nativeness, that shaped the ecological effects of large mammalian herbivores.

Stressed sufficiently, the dominance of such traits over trait carriers becomes self-evident: A given prey species does not care about the genome or morphology of its primary predator, save to the degree that these things influence its behavior — that is to say, to the degree that they modulate traits. Should an entirely unrelated species possess the same predatory capacities and proclivities, the difference in phylogeny would be rather unimportant to an antelope about to be eaten. That we cannot, nevertheless, discount the trait-bearers and the species-level view from ecological considerations is because all creatures carry not one or two or even a handful of ecological traits, but dozens if not hundreds. 

Traits — size, diet, metabolism, reproductive rates — come bundled, and it is therefore exceedingly rare to find two species that are, in fact, exactly one-to-one equivalent. A water buffalo and an extinct marsupial may be essentially comparable regarding some of their ecological traits, including, perhaps, the most decisive ones, but they will invariably differ in others. The decisive question, then, is what degree of similarity may suffice. The dingo is not a thylacine; its ecological effects do not correspond exactly. Neither would those of leopards or tigers to the extinct marsupial lions, nor even of the Komodo dragons to their vanished Aussie relatives. Is it, however, “more unnatural” to have the “wrong” Australian top predators, or to have no top predators at all?

Once integrated, these concepts may provide a flexible, workable basis for thinking of natural systems. Forgive the rather dry summation: Ecosystems are self-ordering constellations of trait interactions transcending the particular species that make them up and contingent on the physio-chemical factors that constrain them. In other words, an ecosystem is more than the sum of its parts. It is an emergent system whose stability inheres in the various roles its constituent species fill.

Individual species may be replaced or simply lost, but so long as the keystone traits, and the interactions between them, remain in place, the ecosystem may endure in something like “homeostasis.” It is the trait, not the trait carrier, that is fundamentally native to the system. Nativity at the species level, then, is perhaps best understood as the state of integration into a preexisting, superordinate web of interrelated roles and functions. 

The ancient Greeks wrote and sang much on the theme of νόστος or “homecoming.” In our time we ought, perhaps, to reflect on the concept of becoming at home. None would think to deny today’s Māori their nativeness to New Zealand, yet in the days of Kupe’s great canoes when their ancestors drew ashore, they were new to the land. 

Nativeness in human societies is a topic and a quandary of its own, yet the conceptual overlap is inescapable. Belonging, home and fittedness to place — these are not concepts we can eschew altogether without throwing the world, and our understanding of it, into jeopardy. Clearly, the association of the giant panda with China and the kiwi with New Zealand is not merely a matter of arbitrary perceptions. Yet neither can we fence out all the dingos and their likes, nor insist upon criteria for nature more static than the natural world itself. 

Ecological systems, and the associations that constitute them, are real and crucial. It is only that we cannot, in our shifting, changing world, be rigid to the point of blindness, lest we lose our grasp on the very things we are trying to preserve.