Hello Interactors,

It’s been awhile as I’ve been enjoying summer — including getting in my kayak to paddle over to a park to water plants. Time on the water also gets me thinking. Lately, it’s been about what belongs here, what doesn’t, and who decides? This week’s essay follows my trail of thought from ivy-covered fences to international borders. I trace how science, politics, and even physics shape our ideas of what’s “native” and what’s “invasive.”

INVASION, IVY, AND ICE

As I was contemplating this essay in my car at a stop light, a fireweed seedling floated through the sunroof. Fireweed is considered “native” by the U.S. Government, but when researching this opportunistic plant — which thrives in disturbed areas (hence it’s name) — I learned it can be found across the entire Northern Hemisphere. It’s “native” to Japan, China, Korea, Siberia, Mongolia, Russia, and all of Northern Europe. Because its primary dispersal is through the wind, it’s impossible to know where exactly it originated and when. And unlike humans, it doesn’t have to worry about borders.

So long as a species arrives on its own accord through wind, wings, currents, or chance — without a human hand guiding it — it’s often granted the status of “native.” Never mind whether the journey took decades or millennia, or if the ecosystem has since changed. What matters is that it got there on its own, as if nature somehow stamped its passport.

As long time Interactors may recall, I spend the summer helping water “native” baby plants into maturity in a local public green space. A bordering homeowner had planted an “invasive species”, English Ivy, years ago and it climbed the fence engulfing the Sword Ferns, Vine Maples, and towering Douglas Fir trees common in Pacific Northwest woodlands. A nearby concerned environmentalist volunteered to remove the “alien” ivy and plant “native” species through a city program called Green Kirkland. Some of the first Firs he planted are now taller than he is! Meanwhile, on the ground you see remnants of English Ivy still trying to muster a comeback. The stuff is tenacious.

This is also the time of year in the Seattle area when Himalayan Black Berries are ripening. These sprawls of arching spikey vines are as pernicious as they are delicious. Nativist defenders try squelching these invaders too. But unlike English Ivy, these “aliens” come with a sugary prize. You’ll see people walking along the side of roads with buckets and step stools trying their darnedest to pluck a plump prize — taking care not to get poked or pierced by their prickly spurs.

This framing of “invasive” versus “native” has given me pause like never before, especially as I witness armed, masked raids on homes and businesses carried out by U.S. Immigration and Customs Enforcement (ICE) agents. These government officials, who are also concerned and deeply committed citizens, see themselves as removing what they label “invasive aliens” — individuals they fear might overwhelm the so-called “native” population. As part of the Department of Homeland Security, they work to secure the “Homeland” from what is perceived as an invasion by unwanted human movement. In reflecting on this, I ask myself: how different am I from an ICE agent when I labor to eradicate plants I have been taught to call “invasive” while nurturing so-called “native” species back to health? Both of us are acting within a worldview that categorizes beings as either threats or treasures. At what cost, and with what consequences?

According to a couple other U.S. agencies (like the National Park Service and the U.S. Department of Agriculture) species are considered native if they were present before European colonization (i.e., pre-1492). The idea that a species is “native” if it was present before 1492 obviously reflects less a scientific ecological reality than a political opinion of convenience. Framing nativity through the lens of settler history rather than ecological process ignores not only millennia of Indigenous land stewardship, but prehistoric human introductions and natural migrations shaped by climate and geology. Trying pin down what is “native” is like picking up a squirming earthworm.

These little critters, which have profoundly altered soil ecosystems in postglacial North America, are often labeled “naturalized” rather than “native” because their arrival followed European colonization. Yet this classification ignores the fact that northern North America had no earthworms at all for thousands of years after the glaciers retreated. There were scraped away with the topsoil. What native species may exist in North America are confined to the unglaciated South.

What’s disturbing isn’t just the worms’ historical presence but the simplistic persistent narrative that ecosystems were somehow stable until 1492. How is it possible that so many people still insist it was colonial contact that supposedly flipped some ecological switch? In truth, landscapes have always been in motion. They’ve been shaped and reshaped by earth’s systems — especially human systems — long before borders were drawn. Defining nativity by a colonial decree doesn’t just flatten ecological complexity, it overwrites a deep history of entangled alteration.

MIGRATION, MOVEMENT, AND MEANING

If a monarch butterfly flutters across the U.S. border from Mexico, no one demands its papers. There are no butterfly checkpoints in Laredo or Yuma. It rides the wind northward, tracing ancient pathways across Texas, the Midwest, all the way to southern Canada. The return trip happens generations later — back to the oyamel forests in the state of Michoacán. This movement is a marvel. It’s so essential we feel compelled to watch it, map it, and even plant milkweed to help it along. But when human beings try to make a similar journey on the ground — fleeing drought, violence, or economic collapse — we call it a crisis, build walls, and question their right to belong.

This double standard starts to unravel when you look closely at the natural world. Species are constantly on the move. Some of the most astonishing feats of endurance on Earth are migratory: the Arctic tern flies from pole to pole each year; caribou migrate thousands of miles across melting tundra and newly paved roads. GPS data compiled in Where the Animals Go shows lions slipping through suburban gardens and wolves threading through farmland, using hedgerows and railways like interstates. Animal movement isn’t the exception; it’s the ecological norm.

And it’s not just animals. Plants, too, are masters of mobility. A single seed can cross oceans, whether on the back of a bird, in a gust of wind, or tucked into a canoe by a human hand. In one famous case, researchers once proposed that a tree found on a remote Pacific Island must have arrived via floating debris. But later genetic and archaeological evidence suggested a different story: it may have arrived with early Polynesian voyagers — people whose seafaring knowledge shaped entire ecosystems across the Pacific.

DNA evidence and phylogeographic studies (how historical processes shape the geographic distribution of genetic lineages within species) now support the idea that Polynesians carried plants such as paper mulberry, sweet potato, taro, and even some trees across vast ocean distances well before the Europeans showed up. What was once considered improbable — human-mediated dispersal to incredibly beautiful and remote islands — is now understood as a core part of Pacific ecological and cultural history.

Either way, that plant didn’t ask to be there. It simply was. And with no obvious harm done, it was allowed to stay.

We humans can also often conflate our inability to perceive harm with the idea that a species “belongs.” We tend to assume that if we can’t see, measure, or immediately notice any negative impact a species is having, then it must not be causing harm — and therefore it “belongs” in the ecosystem. But belonging is contextual. It can be slow to reveal and is rarely absolute.

British ecologist and writer Ken Thompson has spent much of his career challenging our tidy categories of “native” and “invasive.” In his book Where Do Camels Belong?, he reminds us that the “belonging” question is less about biology than bureaucracy. Camels originated in North America and left via the Bering land bridge around 3–5 million years ago. They eventually domesticated in the Middle East about ~3,000–4,000 years ago to be used for transportation, milk, and meat. Then, in the 19th century, British colonists brought camels to Australia to help explore and settle the arid interior. Australia is now home to the largest population of feral camels in the world. So where, exactly, do they “belong”? Our ecological borders, like our political ones, often make more sense on a map than they do in the field.

Even the language we use is steeped in militaristic and xenophobic overtones. Scottish geographer Charles Warren has written extensively on how conservation debates are shaped by the words we choose. In a 2007 paper, he argues that terms like invasive, alien, and non-native don’t just describe, but pass judgment. They carrying moral and political weight into what should be an ecological conversation. They conjure feelings of threat, disorder, and contamination. When applied to plants, they frame restoration as a battle. With people, they prepare the ground for exclusion.

Which is why I now hesitate when I yank ivy or judge a blackberry bramble. I still do it because I believe in fostering ecological resilience and am sensitive to slowing or stopping overly aggressive and harmful plants (and animals). But now I do it more humbly, more questioningly. What makes something a threat, and who gets to decide? What if the real harm lies not in movement