Entangled

Story by  Ben Goldfarb

The epiphany that Christine Wilkinson describes as her “fence awakening” began with a lioness.

In 2016, Wilkinson, a conservation scientist at the University of California Berkeley, was in Kenya exploring conflicts between people and large carnivores. Her research took her to Lake Nakuru National Park, a protected area surrounded by an electric fence built to protect rhinos from poachers. Adjacent to the park lay a ranch, where cattle, sheep, and goats sometimes fell prey to lions and leopards. Usually the ranchers captured and relocated these predators, but, soon after Wilkinson arrived, the property’s managers decided instead to affix a few with satellite collars, among them a lioness with cubs. If they knew where the lions went and how they behaved, perhaps the ranchers would be able to better protect livestock.

It wasn’t long before trouble arose—not for cattle, but for the lioness. Ambling along Lake Nakuru’s fenceline one night, she found a narrow gap at its base and slipped into the park. Soon after, unwitting maintenance workers plugged the hole with boulders, separating the lioness from her cubs. For weeks Wilkinson and others monitored the cat’s tracking collar as she anxiously paced the fenceline. When park staff finally captured and moved her, she was emaciated.

“She hadn’t even tried to hunt during her attempts to get back to her cubs,” Wilkinson recalls. “I started to realize, ‘Oh, fences can really do a lot of different things to animal behavior and ecology.’” She began to contemplate a new research focus: How did fences shape the lives of the wild creatures who encountered them?

At the time, these strips of seemingly innocuous infrastructure had largely escaped formal study—perhaps because fences seem so much flimsier than highways, dams, and other human-built structures. But they are also ubiquitous: Strung together, the world’s fences would likely reach the sun. From that perspective, it was not a stretch to imagine that a few strands of barbed wire or chain link could alter an entire ecosystem.

Starting in 2018, Wilkinson set out to discover exactly what fences were doing to Lake Nakuru National Park. She and other researchers drove and walked the perimeter of the park’s fence, looking for places where animals had penetrated the barrier. They found 175 gaps, likely maintained by the relentless digging of spotted hyenas and warthogs, and put motion-activated camera traps on some of them. Over the next year, Wilkinson’s cameras recorded more than 65,000 animals approaching the park’s fences, and around 3,600 successful crossings by over two dozen species, from leopards, who limboed under the bottom wire, to vervet monkeys, who scampered over the top. Even a rogue giraffe managed to pass through. “I still have no idea how that happened,” Wilkinson says.

The park’s fence, Wilkinson soon realized, functioned as a “sieve,” letting some animals in and keeping others out. For resourceful species like baboons, it wasn’t much of an obstacle. But other animals, particularly large ungulates such as rhinos, elands, and zebras, seldom breached it. By acting as an ecological filter, the barrier altered wildlife communities on both sides. For every fence, says Wilkinson, “there are ecological winners and losers.”

Rather than describing fences as inherently good or bad, then, Wilkinson and a small cadre of fellow “fence ecologists” now seek to better understand these long-ignored features. They’ve called for a “robust field” that investigates the interactions between fences, wildlife, ecosystems, and society, with the goal of better managing what they describe as “one of humankind’s most pervasive alterations of our planet.”

Although fence ecology is nascent—the paper that coined the discipline was published in 2018—its practitioners have already generated a profound insight: Among all the forms of infrastructure with which humans have fettered the planet, few have changed our landscapes more, with less fanfare, than the humble fence. Fences truncate and direct animal movements, shape the distribution of native and invasive species, and dictate interactions between predators and prey. They control the spread of disease and the flow of genes; they alter soil and vegetation and water. Yet for all that, scientists know little about precisely how many are out there, or where they’re located—though their construction is booming around the world. You might even say we’re living in the Wirocene, the age of the fence. 

Not long ago, while driving across a snow-dusted plateau near my home in Colorado, I witnessed an excruciating display of fence dynamics. A yearling elk raced back and forth along a stretch of roadside barbed wire, desperately trying to reach his herd in the field beyond. The adults had jumped the fence without trouble, but not so the yearling, whose heaving chest was damp with blood. I pulled over to watch, a mistake that worsened the elk’s panic and sent him sprinting back across the highway and over a berm. Heartbroken, I drove on, hoping that the yearling and his companions would somehow reunite.

My observation was archetypal: While the formal study of fence ecology is a recent phenomenon, biologists have long recognized that fences are capable of curtailing animal movements. An early demonstration came in Botswana, where, beginning in the 1970s, the European Union compelled the government to erect fences dividing livestock from wildlife, in order to avert the spread of disease into cattle bound for export. The fences lopped off migration routes and prevented wildebeest and other wild animals from reaching watering holes; at one game reserve, tens of thousands perished. Similarly, in October 1971 in Wyoming, a blizzard drove a herd of pronghorn to seek snow-free ground to the south. When a roadside fence blocked their path, more than 3,000 died—killed by starvation and exposure, yes, but also by the thin line of wire. In Australia, eastern long-necked turtles got entangled in pest-exclusion fences; in Scotland, fences clotheslined grouse and other low-flying birds. The more evidence that mounted, the more alarmed scientists became. “It’s not like we didn’t know that fences were problematic for wildlife,” an ecologist told me once. “But when you look at the density (of fences) and you scale it up in your head, it’s like, holy shit.”

Among the first studies to focus directly on fences was conducted in the early 2000s, when a pair of wildlife biologists, Justin Harrington and Michael Conover, surveyed more than a thousand kilometers of fenceline across sagebrush steppe in Utah and Colorado. The duo found the carcasses of 133 elk, mule deer, and pronghorn who had become tangled in fences, and calculated that one animal perished per year along every four kilometers (2.5 miles) of fence. They found still more corpses nearby, primarily juveniles who’d been cornered by predators or had grown exhausted from futilely pacing the fenceline. Most victims had snagged a rear hoof on the top wire while leaping over, kicked wildly, and snarled themselves further. Deadliest were fences that combined woven-wire—tight rectangular panels of fencing—with a top strand of barbed wire, which, the biologists wrote, would “cinch the ungulate’s leg… into the top rung of the woven-wire fencing.”

Fences warp behaviors and ecosystems in subtler ways, too. Even pronghorn that succeed in crawling under fences can lose hair as the bottom wire chafes their backs, leaving them less insulated against the harsh winters that characterize much of their range. Dingo-proof fences in Australia built to prevent the canids from killing sheep have allowed nonnative foxes to proliferate, to the detriment of some native marsupials. In South Africa, game fences disproportionately funnel browsing elephants to the middle of protected areas, where their concentrated impacts can degrade habitat. 

As Wilkinson notes, however, fences also create occasional beneficiaries—picture a hawk or a shrike scanning for prey from atop a fencepost. Fences are ambivalent features, capable of harming biodiversity and promoting it; the same fence that blocks elk movement might also prevent livestock from overgrazing a riparian area. In Australia, fences have protected native marsupials from feral cats; in New Zealand, they’ve defended rare birds and skinks from invasive stoats and possums. Around the perimeter of South Africa’s Hluhluwe-iMfolozi Park, so-called “smart fences” beam instantaneous alerts to rangers whenever a poacher attempts to break through, facilitating the conservation of rhinos.

One particularly effective application of fences is along roadsides, where barriers can prevent animals from darting into traffic and funnel them to safe wildlife passages over and under roads. “When I first got into this business, I said, why do we need so much damn fencing?” a road ecologist named Patricia Cramer told me. But ample research suggests that elk and other animals don’t generally gravitate to wildlife crossings unless they’re forced to use them by a surrounding 2.5-meter (eight-foot) high wall of wire. “You can increase the number of movements (through a crossing) by a hundredfold” with fences, Cramer acknowledges.

This is the paradox of fences: For all their environmental ills, they can also safeguard wild animals from the panoply of human-generated forces—cars, poachers, invasive species—that would otherwise harm them. “Is fencing important for wildlife management, or does it have negative impacts on wildlife?” asks the ecologist Andrew Jakes, lead author on the 2018 paper that first described fence ecology. The answer is, well, yes. “It really depends on where you’re putting this fencing out on the landscape,” Jakes says, “and what the fencing looks like.”

But fences aren’t just popping up—in some places, they’re also coming down. 

One winter morning, I drove to Evergreen, a town tucked in the mountains west of Denver. There I rendezvoused with Christie Greene and Sara Barnas, leaders of Wild Aware, a group that’s trying to make their Colorado community slightly less fence-bound. Greene originally founded the organization in 2019 to tackle the town’s deer and elk roadkill problem, but, on a hike near her home one day, she noticed a twisted jumble of barbed wire along the trail. This wasn’t unusual in Evergreen, where many former ranches have become public parks. Greene decided to launch a new program, Barbed Wire Warriors, that would marshal volunteers to remove derelict fences; Barnas, a member of Wild Aware’s board, became the program’s czar. The group has since cut up and carted away 14 separate areas of fencing comprising more than 5.7 kilometers (3.5 miles) of barbed wire, nearly all on public parkland. (Most of that material has gone to a metal recycling factory, though some has been claimed by a local artist.) Volunteering “is getting to be so popular,” Greene said. “It kind of sells itself.”

Greene and Barnas drove me around Evergreen to show me what they were up against: fences snarled along highways, stretched between properties, running pointlessly through open fields. We rolled past a county park and Greene, a compact woman with the tensile energy of a stretched steel cable, told Barnas to stop. A few strands of barbed wire drooped between posts, holding back nothing; some lay on the ground, a jagged birds-nest.

“This is nasty,” Barnas said with a frown. “The downed stuff is the worst; the animals get tangled up.”

“I’ll call the county right away,” Greene said.

And so the day went: Fences, fences, everywhere, most of them having long outlived their historic purpose. Fences, I was learning, were so ubiquitous they were invisible, the wiry backdrop against which our lives and landscapes unfold. If I hadn’t been looking for them, I wouldn’t have noticed them, though they stood, or lay coiled, in plain sight.

Evergreen is no anomaly. A surfeit of barbed wire spiderwebs Colorado and other states in the American West, where the Wirocene has held sway since the businessman and farmer Joseph Glidden patented modern barbed wire in 1874. Whereas cattle frequently broke smooth wires by leaning against them, the sharp points of “thorny fence” repelled the animals. Nearly from its inception, critics lamented the violence of barbed wire: “Scarcely a day passes but one can hear of the death or fatal injury of a cow, calf, horse or colt,” observed a report for Denver’s Daily News in 1882, “which has run into the fence… and so cuts its head and body.” But the brutality of barbed wire was, in a sense, the point—it was how the western commons was domesticated and privatized, the means with which powerful cattle interests excluded their rivals, wild animals, and Indigenous people. Not for nothing did some Native tribes refer to it as the “devil’s rope.”

By the early 2000s, scientists and conservationists had begun to ask what a less harmful fence might look like—among them Harrington and Conover, the biologists who chronicled the fence-caused deaths of deer and other ungulates in Colorado and Utah. Replacing woven mesh with smooth wire, lowering top strands, and raising bottom wires, they wrote, would make fences easier to jump, shimmy through, and slide under. Moreover, such retrofits benefited landowners as well as animals: Thrashing deer and elk frequently damaged fences, forcing ranchers to shell out for costly repairs. “(T)he cost of modifying fences,” Harrington and Conover wrote, “may be less than the economic costs associated with fence mortalities and fence repair.”

Land managers have since developed formal specifications for wildlife-friendly fencing. Agencies such as Colorado Parks & Wildlife now recommend that top wires be no more than 107 centimeters (42 inches) off the ground, and that bottom wires provide at least 40 centimeters (16 inches) of clearance. Smooth wire is preferable to barbed, three strands are preferable to four, and anything is better than woven wire. The addition of reflective tape and vinyl strips makes fencing more visible to greater sage grouse and other low-flying birds. And fences with removable sections or gates can easily be opened to permit wildlife movement when livestock aren’t on the land. Fence modification, says the ecologist Jakes, “is going to maintain and increase our wildlife populations, and it’s going to be a benefit to the private landowner. So we see it as a win-win.”

The extent to which fence removal and replacement is already occurring, however, isn’t easy to determine. There’s no single entity in charge of managing or monitoring such projects, but rather an atomized network of small, scrappy groups like Wild Aware. In Arizona, a coalition called the Desert Fence Busters has taken down more than 32 kilometers (20 miles) of barbed-wire, while the Oregon Natural Desert Association has eliminated 480 kilometers (300 miles) of fence—and replaced others with pronghorn-friendly wire within a national wildlife refuge. Hundreds of kilometers more have been torn from antelope migration routes in Nevada, mountain goat habitat in Idaho, and ungulate winter range in Montana. The Absaroka Fence Initiative, a collection of nonprofits, agencies, and landowners in northwest Wyoming, has removed 22.5 kilometers (14 miles), modified 27 kilometers (17 miles) more, and recycled more than 20,000 pounds of fence material. And the Sage Grouse Initiative—a westwide program that tasked ranchers with voluntarily conserving rangelands to prevent the bird from being declared an endangered species—removed or added high-visibility markers to more than 800 kilometers (500 miles) of grouse-threatening wire.

But while those projects, and many, many others, have collectively obliterated or altered thousands of fence miles, their efforts remain dwarfed by barbed wire’s awesome scale. Per one 2021 study in the Journal of Applied Ecology, the average mule deer in western Wyoming encounters around 120 fences per year. The average pronghorn? Two hundred and fifty. The American West remains latticed by more than a million kilometers (620,000 miles) of fence—enough to encircle the earth more than 75 times.

Would-be fence reformers face big challenges elsewhere, too—for, in many ways, the Wirocene is deepening its global hold. As the journalist Jim Robbins has observed, nations around the world are fortifying border infrastructure; the U.S.’s southern border wall stands to thwart the wanderings of jaguars, while China’s border fence with Mongolia frustrates gazelles. The privatization of once-communal land has also exacerbated the Wirocene. In Tibet, the installation of property-line fences in 2004 partitioned vast pastures into small ones, concentrating yak grazing and damaging alpine grasslands. In southern Kenya, rural landowners have constructed nearly 40,000 kilometers (25,000 miles) of fences, squeezing out wildlife and traditional pastoralists alike and encouraging rampant land speculation.

There, as in the American West, fences have a potent cultural valence. They are never mere strips of wire and wood; they are instruments of social control and the consolidation of economic power. Given their outsized societal impacts, it’s no wonder their environmental effects get overlooked. “Fences are viewed as a symbol, not necessarily an ecological tool,” Wilkinson says. They are the lines with which we delineate our property, the distinctions we erect between the wild world and the human-built one. Last year, my wife and I constructed an inglorious deer-proof barrier of cedar pickets to protect the native shrubs we’d planted in our backyard. Though I was, in a sense, deliberately curtailing ungulate movement myself, I’d rarely felt more accomplished, nor prouder of the minor claim I’d staked upon the land.

But the symbolic might of fences isn’t always an obstacle to their removal. In places such as Montana, Oklahoma, and Washington, some physical fences are already being replaced by digital ones. The “virtual fence” is a straightforward technology with transformative potential: Ranchers put tracking collars on their livestock, then use an app to draw digital boundaries around the “pasture” in which they want to enclose them. Any cow who approaches the perimeter hears a beep from her collar and, if she keeps going, receives a mild shock. Over time, cattle learn to associate the collar’s audio stimulus with its physical one: If you hear beeping, stay back! Virtual fences offer many of the advantages of physical barriers and few of the downsides, while their flexibility—a polygon on an app is a lot easier to reconfigure than long stretches of barbed wire—suggests novel benefits. Virtual fences could theoretically be used to eliminate blockages to animal migrations, protect stream restoration sites, bunch up cattle so they’re less vulnerable to predation, direct cows to nosh on invasive weeds, and on and on. “There’s all kinds of ways we think we can be creative,” says Natalie Allio, a central Colorado rancher and the cofounder of a virtual fence pilot program.

In 2022, Allio, then working with the Central Colorado Conservancy, partnered with the Forest Service and a coalition of nonprofits to scrape together grant funding for half a dozen local ranchers to experiment with virtual fences while grazing their cattle on public land. The technology hasn’t proven perfect—deep canyons, for instance, can prevent collars from communicating with the radio towers that monitor cows’ locations—and not every user has mastered it. “Most of our ranchers are over 60, and when you’re asking someone in that demographic to adopt a new technology, there’s a learning curve,” Allio acknowledges. Still, some cattlemen have already reaped significant benefits, for example by shunting their cows toward portions of their allotment that can tolerate more aggressive grazing. “One rancher felt that they got an extra six weeks of grazing because they could better utilize their forage,” Allio says.

Early hiccups notwithstanding, to Allio’s mind, virtual fences could eventually prove transformative. They allow ranchers to save on fuel by keeping tabs on their livestock remotely, and obviate the costly barbed-wire repairs that suck up ranchers’ time and money. “We’re learning that there’s enormous potential as the technology improves and operators get better at using it,” Allio says. “There’s a lot of hope around this tool.” 

For now, however, the most effective way to tackle fences remains the simplest: get the obsolete ones off the land.

In Evergreen, home of Wild Aware’s Barbed Wire Warriors, that process is slowly unfolding. Although the group began by lopping down and removing fences on public property in collaboration with government agencies, requests from private landowners soon began pouring in. Today their waiting list is more than a dozen properties long.

“As the word gets out, we’re just getting slammed with requests,” Christie Greene told me as we drove around town, ogling fences. Like all community-centered work, courting residents requires tact and charm; recently Greene and Barnas had learned of a local curmudgeon with an elk-blocking fence. “I’d better bring him cookies,” Barnas said.

Usually, though, it’s the fence that’s prickly, not the landowner. Barbed Wire Warriors’ workdays are grueling and sharp: “If you’re not bleeding, you’re probably not working hard enough,” Einar Jensen, the program’s co-leader, had half-joked to me before I visited Evergreen. (Barnas recommends eye protection and welding gloves.) Still, the gratification of freeing a shackled landscape in a single afternoon has enticed close to one hundred volunteers. “People walk away feeling very accomplished,” Barnas said.

Greene and Barnas took me to see one emblematic project at Dedisse Park, a 420-acre swath of public land much loved by elk. In 2021, Wild Aware volunteers and park staff had cut up and trucked away 240 meters (800 feet) of decrepit ranch fencing that lay in menacing piles on the park’s pine-needle floor. Now we strolled through open stands of ponderosas and past jumbles of boulders. Elk and deer hoofprints scored the wet snow. It was a pleasant place, though truthfully there wasn’t much to see. But that, of course, was the point.