My nonstop flight from New York to LAX is arriving and the crackle-soft voice of the flight attendant shifts me in my window seat. Through the small pane of glass I can see my hometown of Yorba Linda creeping up the foothills of Orange County, indistinguishable from the rest of the Southern California megalopolis. My slow-fade window backdrop had started with eastern forests that melted into crop circles, then into meandering shades of desert tan. In short order, the tangle of north-south ridges that divide Southern California’s coastal plain from its high desert gave way to the bedazzling microchip geometry of sprawling civilization. With the ocean on one side, mountains on the other, and sparkling humanity in between, the lines drawn dividing culture from nature were all too visible.

As a kid growing up in Orange County, nature was this place we drove to. Each summer, my family would pack into the minivan for a whirlwind tour of Yellowstone, Yosemite, or Mount Whitney. Pristine places, pine-scented air, fishing, and long meandering hikes. In the cooler months we might camp among the Joshua trees of the high desert, but we were always going to nature. It didn’t seem to bother us that subdivisions and mini-mansions steadily devoured the chaparral hillsides and historic orange and avocado groves of our once-sleepy corner of the county, so long as each summer we could flee to pristine places far from the smoggy, fast-paced life of the suburbs.

Our ancestors had supposedly reclaimed this desolate wilderness from the “idle savage” and hostile Mother Nature. In the good old days, Orange County was promoted as a Garden of Eden paradise, boasting mild temperatures, millions of acres of lush irrigated vegetable gardens, and fruit orchards surrounded by undulating hills of oak and sage. But after the post-World War II boom, the “Orange” in Orange County became just another hue on the planners’ palette: pastel, pavement, repeat. Today, we certainly wouldn’t use the word “natural” to describe Orange County, or assume that things like “ecology” have much to do with this sprawling empire. That’s certainly how I felt when I left home as a 20-something hoping to make a connection to nature through various back-to-the-land internships, graduate degrees, and backpacking treks.

I was certainly not alone in seeing the world this way; our modern civilization has inherited 500 years or so of talking about the human domain — culture — as totally separate from just about everything else — nature. Look at any map of the world, and the defining boundaries are those between land and sea, countries, and most often around nature. The lines that mostly began in our heads, the ones we used to draw neat and tidy boundaries around ourselves and around nature, have become real in the way we construct our cities and live our lives. Southern California is full of these lines — not only between the United States and Mexico, but also between the myriad municipal, state, and national parks that embellish the coasts, wetlands, and mountains of the Golden State.

I have been reading a lot about these lines and boundaries we have drawn in the cultural sand; about how these lines and boundaries have hurt people, and places; and about how in an era of climate change, they might even be threatening our very existence. I am beginning to wonder if perhaps we should get rid of them, or at least redraw them. So each time I return to the County of Orange — for holidays, birthdays, births, backpacking trips with my brothers  —  the lines that seemed so clear to me growing up blur just a little bit more, and the differences between “us” and “them” slowly fade into thin air.

During my most recent trip, while strolling through the familiar streets of my childhood, I stumbled upon a cherished row of eucalyptus trees (Eucalyptus globulus) that lines a nearby street. A pickup truck’s worth of workers were cleaning up after their morning task, and the soft consonants of Spanish bounced from mouths to ears. It appeared that they had just finished delimbing one of the eucalyptus trees, which stood stark and naked among its shaggy-clad companions. One of the workers prepared to make a final cut at the base of the trunk. As his chainsaw sputtered and choked, my mind began to wander in sync with the whine of metal teeth incising the fat, tan trunk. I passed by these trees almost daily growing up and never really put them into any kind of historical or ecological context. I had recently been reading about the natural history of Orange County and though I knew these trees were old, it now made sense that they had no doubt been planted to protect orange groves that had once covered the county against the Santa Ana winds.

I watched as the first few inches of the saw’s sweep transected the tree’s outer bark and newest growth rings. The tree rustled and I imagined the blade cutting through the growth rings that correspond to my 30-something years of life on this earth. It would pass by rings made during my time in graduate school and college, the two years spent as a Mormon missionary in the Dominican Republic, high school, my first kiss, first camping trip, and my birth.

One by one, the rest of the crew stopped their tasks and began watching the tree for signs of tilt as the blade continued past growth rings made in the 1970s, when the orange and avocado groves the eucalyptus protected were being swallowed whole by subdivisions and strip malls (my parents’ home was built during this time). As the blade cut deeper, and the tree’s once-flesh-now-dust flew into the air, it passed the 1960s — Nixon, hippies; 1950s — Cold War; 1940s — WWII; 1930s — depressions, dust bowls; and 1920s — prohibition and revivals. Buried deep inside the bole of the tree, the blade approached the growth rings of 1913, the year the first avocado trees were planted, and the year Richard Nixon was born, just down the street from where I stood.

Finally, the sawyer cut through the teetering eucalyptus’s infant growth rings, which must have been laid around 1910, when the Janss Investment Company purchased a portion of the Rancho Cañon de Santa Ana and began subdividing it into ten- and 20-acre agricultural parcels which would later become Yorba Linda.

With a snap and a crack the truncated bole thudded to the path along the sidewalk and the sawyer quickly began to buck it into manageable sections. One of the other workers directed the few backed-up cars to pass, and as I walked past the downed eucalyptus and crew, I caught the tail end of a scowl cast by an older woman in a black Mercedes as she surveyed the scene and sped off. For many in California, illegal immigration is a touchy subject. Perhaps she was sizing up the tan-skinned workers as possible suspects — lines and boundaries.

Like the Europeans, Mexicans, Chinese, and other ethnicities that call California home, eucalyptus trees are immigrants. Native to Australia, they were brought to California during the gold rush of 1849 with one of the thousands of Australians who left Sydney hoping to strike it rich. And like the immigrants they accompanied, the eucalyptus found fertile soil and a favorable climate in the California coastal sage and prairies. For a few years thereafter the eucalyptus was officially promoted as a “wonder tree” that would save California from an impending timber famine and whose pungent leaves were reputed to have medicinal properties. Many soon realized, however, that the structural properties that gave eucalyptus its reputation as a good timber tree had come from the wood of centuries-old groves in southern Australia. The wood of the fast-growing young trees, saturated with water, warped and cracked when harvested in California and was therefore useless. Although commercial production came to an abrupt halt, the tree naturalized itself throughout the coastal region of central and southern California.

Eucalyptus has since become such an iconic part of California’s scenic heritage that there is an entire landscape painting genre named after it. However, in an age of ecological correctness, the eucalypts have become easy targets for those who are trying to restore nature to some semblance of what it once was before we came along and bulldozed everything in the name of culture.

One way of restoring ecological integrity is to get rid of plants and animals that did not evolve in a given ecosystem, the plants and animals most often called nonnative, exotic, or alien species. These plants were either brought here intentionally or hitched a ride with us. However, despite the hundreds of nonnative species that have naturalized since the European colonization of the Americas, in California the eucalyptus has been singled out as a symbol of a gaggle of ecological menaces known as “invasive” species. In his 2002 article “America’s Largest Weed,” ecologist Ted Williams calls for the total removal of eucalypts or, as he refers to them, “eucs.” For restorationists like Williams, eucalypts simply do not belong in California, despite their ability to adapt to our climate.

California ecologists have in many cases removed eucalypts from public lands in order to restore native chaparral and coastal ecosystems, though hundreds of other nonnative plants remain in these parks. In the Channel Islands National Park, just off the coast of Southern California, officials have decided to keep some eucalypts that are close to historic structures as part of the <em”>cultural heritage of the parks, while removing them from other parts of the island.

As I continued my walk toward the mesquite hills above my parents’ subdivision, it struck me that the language used to talk about eucalypts as an ecological menace and the language used to ostracize illegal immigrants as social pariahs is similar. Both discourses make use of epithets — “eucs” or “wetbacks” — to distance and demonize. Both eucalypts and immigrants are often derided for uncontrolled reproduction and the danger they pose to native ways of life, whether that be biological competition for growing space or economic competition for jobs. In a strange twist the eucalypts are anthropomorphized in order to be dehumanized, and illegal immigrants are dehumanized in order to be de-naturalized. Lines and boundaries.

Ironically, the debate over removal of eucalyptus trees from spaces delineated as “natural” exposes how drawing a stark boundary between culture and nature is not so easily accomplished. Those who love the eucalyptus accuse folks like Ted Williams of ecological purism, or of engaging in a kind of arboreal “ethnic” cleansing in the name of native floral supremacy. Williams and others have argued that protecting native species is, in the end, about protecting global biodiversity in the face of the supposed homogenizing effect of invasive exotic species like eucalyptus.

However, as Emma Marris shows in her book Rambunctious Garden, global extinction caused by invasive species is relatively rare, especially by relatively benign exotics like eucalyptus. Extinction from invasive species is mostly happening on small islands such as Guam where the brown tree snake, introduced to Guam after World War II, has decimated bird populations. Eucalyptus trees have not caused the extinction of a single species; while the trees have had a negative impact on some birds whose beaks are sealed shut by eucalyptus sap, they also provide critical winter habitat to migrating monarch butterflies and other native species that have now adapted to them.

Certainly my ancestors were once immigrants. And certainly all native plants on the Channel Islands arrived in succession. So, if eucalypts have adapted to California, and are not causing widespread extinction, why should we spend precious resources to remove them? Lines and boundaries.

I am not saying that all human activity is benign; it is not. We must undo the damage we have inflicted onto this planet. Nor am I advocating for an abandonment of the protected-area franchise, which has protected millions of species from our lust for money and power. But what both the Channel Islands case and the woman in the black Mercedes say to me is just how deeply ingrained the boundaries we draw around the other can become — between culture and culture, and between culture and nature. It is time to rethink these lines and boundaries.

As I sit in the airport terminal waiting for my return flight to the East Coast, I notice a small house sparrow dip and weave through the airport corridors. Even in a world where we have laid an iron curtain between culture and nature, there are always cracks where the two bleed together. The domains of culture and nature don’t exist independently. Even a place as developed and overrun by Homo sapiens sapiens as Southern California shares something of the infinite complexity that emerges between these cracks. The good —  if sometimes scary — news is that the cracks are getting bigger.

The moral to the story is not that one can find “nature” in Orange County if one would just look hard enough; nor is it that intact, robust ecosystems are not important, or that they are wholly social constructions. But in a world of increasing ecological catastrophe, the solution is not necessarily to ramp up our technological strength over a more aggressive “nature”; nor is it necessarily to bring back pristine ecologies by removing every last scrap of nonnative species.

This is because ecology is not a place —  it is not a thing we have control over; ecology is the space between things, including us. Believing that there are natural places and natural things, and totally separate cultural places and cultural things, denies the inherent beauty, creativity, agency, and interdependence of all things, even eucalypts and immigrants. Climate change doesn’t care whether our parks look the same as they did two hundred years ago, and human compassion does not respect borders between nations.

There are no easy answers moving forward; surely we must do something different if we are to survive as a species. But rather than continuing to police the boundaries between ourselves and the other, perhaps the task ahead is to dismantle the boundaries we have constructed between ourselves and everything else and to watch what happens.

This essay appears in Coming of Age at the End of Nature edited by Julie Dunlap and Susan A. Cohen and published by Trinity University Press. Reprinted courtesy of Trinity University Press. For more information, please visit www.tupress.org.