by Jon Mooallem
Cottle was a huge, barrel-chested patrolman whose powerful fist, it was said, was more effective than his billy club. He’d performed heroically during the earthquake and fire of 1906 and once infiltrated a masquerade ball dressed as the duke of Wellington to catch jewel thieves. In a 1910 profile headlined “By Day He Catches Burglars; By Night He Catches Bugs,” the San Francisco Call presented the cop as a brawny rejoinder to the image of entomologists as “blue spectacled old men, with long hair and pasty faces peering into slimy pools.” Cottle himself had once felt that way about butterfly lovers. But he now understood that collecting butterflies was macho, athletic stuff. He claimed to have once trudged across thirty-eight miles of problematic wilderness in pursuit of a single butterfly, the way hunters tracked bears. (Elsewhere, there were stories of men dangling hundreds of feet down the side of a cliff to capture a particular species of butterfly.) Cottle called butterfly collecting “the healthiest life in the world and the greatest sport I know anything about.” A few months spent charging alongside him would cure tuberculosis, he said—guaranteed.
Boosters played up the monetary value of rare specimens. In the Bay Area especially, all the breathy fantasies of the Gold Rush were recast around butterflies. There were fortunes to be made in these “flying nuggets” of gold—all you had to do was reach up and swing a net. With new laws and conservation organizations like the Audubon Society making other popular naturalist hobbies like bird and bird-egg collecting problematic, some of that attention shifted to butterflies. And while the nature fakers were sympathetically anthropomorphizing wolves and bears, it was tough to feel bad about killing butterflies, particularly since they disappeared en masse at the end of their seasonal flight periods anyway. They were like the leaves, which painlessly dropped from the trees. As one how-to guide for collectors put it: “Their lives are so brief, what can it matter?”
There are no cases in which overcollecting was the major cause of an American butterfly’s extinction, the way overhunting and egg collecting clearly wiped out birds like the great auk. Typically, butterfly species have been imperiled by the same, sometimes interrelated forces that threaten the Lange’s metalmark today: habitat loss or habitat fragmentation, and invasive species. As early as 1875, in fact, Hans Hermann Behr, the absentminded physician, believed that the Xerces blue, a brilliantly blue-winged butterfly found only in San Francisco, had been driven extinct by the city’s expansion. The Xerces was a sand dune species, but its habitat was changing from open sand to residential neighborhoods in Behr’s lifetime. “The locality where it used to be found,” he complained, “is converted into building lots.” And the only insects that might survive in such a place were the “louse and flea.” For Behr, it was only one example of how quickly the natural beauty of the Bay Area was disintegrating.
James Cottle was barely a teenager when Behr lodged these complaints; the landscape that Cottle’s mentor now saw as spoiled was the only one that Cottle had ever known. Nevertheless, by 1928, an aging Cottle felt the same way Behr had at the end of his life, like he’d watched the beautiful terrain of his youth crumble into an ecological ruin. All his favorite butterfly collecting spots in San Francisco had been “erased forever by the city’s growth,” Cottle wrote—“rendered sterile and worthless . . . destroyed, defiled, eradicated.” He saw scarcely any turf left, and focused instead on one day joining his mentor Dr. Behr in heaven. Cottle pictured Behr and all the other old collectors who’d preceded him waiting for him in the afterlife, staking out a tract of prime butterfly habitat “with nets enough to go around.”
Liam O’Brien was doing his survey of San Francisco nearly eighty years later, in 2007. He counted thirty-two species and subspecies of butterflies, about two-thirds of what had been there when Cottle started collecting in the city. “In San Francisco,” Liam told me, “we’re known for what we’ve lost.” The Xerces blue in particular stands as a chastising symbol—the nation’s major invertebrate conservation nonprofit, the Xerces Society, is named for it. It ultimately became the first American butterfly known to be wiped out by humans, though it hung on in San Francisco many decades longer than expected. The butterfly had been presumed extinct for years when, in 1941, two young entomologists happened upon a small number of Xerces near a creek in San Francisco’s Presidio. Ecstatic to see the butterfly still alive, they netted and killed large numbers of specimens to trade with their friends. It was the last time the butterfly was ever seen.
“I always thought there would be more,” one of the entomologists told a reporter near the end of his life. “I was wrong.” His name was William Harry Lange. A few years before the Xerces incident, he’d discovered a new kind of metalmark at Antioch Dunes.
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HARRY LANGE, as he was known, was another native San Franciscan butterfly buff. He was born in 1912 and grew up collecting butterflies before school with an obsessive glee—at the same time, mind you, that James Cottle was on his way out, growing convinced that the city had been trashed. In fact, Lange went to high school within a couple of miles of several other budding entomologists, all of whom were so enraptured by the insects they found while tromping through their city neighborhoods that they pursued the science in college and quickly made names for themselves in the field. The 1930s and early 1940s are now considered a golden era for the science in the Bay Area. When Harry Lange netted his first Lange’s metalmark at Antioch Dunes in 1933, he was merely one in an eager army of young men out there, scouring new and mesmerizing critters from the sand.
During the Depression, it was difficult for entomologists to travel to far-flung places for research. The Antioch Dunes emerged as an alternative study site for entomologists at the universities in Berkeley and Davis—and an endlessly fascinating one. At one time, there may have been as many as four or five thousand insect species living there, sewn symbiotically into the ecosystem. It couldn’t have been a more convenient place to study, either: at the edge of the dunes was a bar called the Little Corral, whose owner allowed the men to park their Model A’s there as long as they bought a beer first, and after a long day of work they could take swims or go fishing in the river. Consequently, probably no place in North America of such a small size has been scrutinized by entomologists so thoroughly, over so many years.
By Labor Day weekend 1954, the dunes were so well-known that, when a regional chapter of the Lepidopterists’ Society had its annual meeting in San Francisco, organizing a field trip to Antioch was a no-brainer. The lepidopterists were coming to see the Lange’s metalmark, and everyone managed to catch one and take it home. Still, Jerry Powell, an undergraduate at Berkeley at the time, later remembered being surprised that the generation just ahead of him—Harry Lange’s generation—had written off the dunes by then. To them, the place was destroyed.
There had already been decades of intermittent sand mining by that time. It began in earnest after the San Francisco earthquake of 1906, when bricks were needed to rebuild the city. But it was especially vigorous when Jerry Powell first visited. At times, two separate companies were hauling sand from five different areas of the dunes at once, shipping it out by truck, river barge, or train. Spurs ran from the nearby railway to the area between the two power line towers, and sand was being shoveled out of that area most intensively, straight onto railcars. A small depression was just starting to be noticeable there: the beginnings of the bowl-shaped valley that I’d find gaping between the power line towers on the property now.
There had also been lots of industrial development around the dunes in the years after World War II, though, according to Powell, the last straw for Harry Lange’s generation would be the construction of the gypsum plant in 1956. Not only did it sprout up in the middle of the habitat, splitting the dunes in half, but it also cast white dust over the place. It felt—in a very visceral way—like an atrocity.
It was all a matter of age and perspective, of course—all part of the same cycle of disillusionment that had been going on in San Francisco. The Lepidop
terists’ Society trip was the first time Jerry Powell had ever been to the dunes, and he and the other students were just as excited by the place as Harry Lange and his contemporaries had been twenty years earlier. Just as Cottle loved the city that Behr wrote off, and Lange loved the city that Cottle wrote off, Powell now loved the dunes that Lange’s generation wrote off. Powell didn’t see a landscape sapped of life. He saw a “terrific variety” of insects. And he was sufficiently captivated to study the ecosystem on and off for decades as a professor at Berkeley.
Two decades later, though, by the mid-seventies, development had winnowed down the dunes even more dramatically. Weeds were rampant, and another recent surge of sand mining had eaten farther into the property than ever before. But Powell was still intrigued. In 1976, he began what could have been a culmination of his research at Antioch Dunes: a study to plot the decline or disappearance of insect species at the dunes since the early 1930s, to describe how that web of life broke down.
Because the dunes had been visited so regularly by entomologists, Powell assumed that the specimens they collected in any given era were a good reflection of the insect life that existed there then. So he and his students searched through museums, where specimens were labeled with information about where and when they were caught, and tallied all the samples brought home from Antioch in two seven-year periods, a decade apart, starting in the 1930s. Meanwhile, Powell made his own trips to the dunes for the next seven years, collecting everything he could. Now he had samples from three seven-year time periods—a chronological catalog of what was netted at the Antioch Dunes on some six hundred different days between 1933 and 1983. By looking at when species were last collected, he could narrow down when they vanished from the ecosystem.
To make the study manageable, Powell had decided at the outset to look at only a fraction of the insect species known to exist at the dunes—376 of them, which still took him twenty-five pages to list. Powell concluded that 243 of those 376 species were now gone. All manner of wasps, beeflies, beetles, robberflies, and velvet ants had disappeared. Among them were four species endemic to the dunes—species, like the Lange’s, that can’t be found anywhere else on Earth. That is, they were not just missing from Antioch; they were now globally extinct.
But there was a serious wrinkle. Powell expected to show the number of species declining during those fifty years. Instead, his data showed the opposite. Even though many species disappeared, the total number of species being collected actually rose over time. Against all odds, biodiversity appeared to be increasing at Antioch Dunes.
He soon realized this was an illusion. Powell thought about entomologists’ nets: how, in his lifetime, their mesh had gotten finer and finer as scientists became interested in catching insects of smaller size. In the thirties, California was full of insects that hadn’t been named—large, alluring, and conspicuous bugs that leapt out at you from the landscape. The boys of Lange’s generation concentrated on the butterflies and dragonflies and wasps—the charismatic megafauna of the invertebrate world. As those larger insects lost their novelty, or their population declined and they became harder to find, the next generation was driven to root around for smaller, more obscure things. And so, in turn, was the generation after it.
Over the years, the gaze of entomologists gradually magnified, each generation scrutinizing what the previous one hadn’t bothered with or noticed. By the time Powell was surveying the dunes in the late seventies and early eighties, the insects he was bringing home included the minuscule and the nocturnal—because that’s what a scientist of his generation was accustomed to collecting, and what was left to be caught.
The biodiversity of the dunes hadn’t expanded. But people’s perception of it had.
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THE PHENOMENON THAT Powell stumbled onto has a name: shifting baselines syndrome. The term was coined in 1995 by a fisheries scientist named Daniel Pauly. Pauly recognized that global fish populations have been slowly collapsing, and though scientists weren’t blind to that damage, their vision was too narrow and subjective to take in its full extent. Every generation of scientist accepts the oceans as it inherits them, Pauly argued. Overfishing may eat away at fish stocks, or even drive species extinct. But when the next generation of scientists start their careers, they don’t see the oceans as depleted; that depleted condition becomes their baseline, against which they’ll measure any subsequent losses in their lifetimes.
Because of this, a comprehensive picture of the changes happening across generations never truly comes into focus. Scientists are concentrating on only part of a line graph that is, in fact, much longer and more steeply plunging. (We now know, for example, that between 1850 and 2005 overfishing reduced the cod population in the northwestern Atlantic by 92 percent.) As we began to fish bigger species like cod into scarcity, we transitioned to eating smaller ones, like monkfish. As Pauly puts it, humans are blindly fishing their way down the marine food web—not any differently from how entomologists blindly moved down the web of insects at Antioch Dunes, with Jerry Powell fascinated by the tiny bugs that his predecessors let pass through the mesh of their nets. When Pauly introduced the idea of shifting baselines syndrome in the nineties, he often joked to the press that kids might soon be enjoying jellyfish salad sandwiches, instead of tuna. These days, he points out that there actually is a commercial jellyfish fishing industry up and running in Asia and the American Southeast.
Shifting baselines syndrome, then, is only the scientific manifestation of a broader problem affecting all people: what the psychologist Peter H. Kahn Jr. has named “environmental generational amnesia.” All of us adopt the natural world we encounter in childhood as our psychological baseline—an expectation of how things should be—and gauge the changes we see against that norm. This explains why the children Kahn has interviewed in terribly polluted neighborhoods in Houston don’t believe their neighborhoods are polluted, and why Kahn’s daughter thinks the woods around their family cabin in Northern California are beautiful and pristine, while Kahn can’t get over no longer hearing the calls of owls. It’s also why Hans Hermann Behr and James Cottle—and even Liam O’Brien today—could all spend their lives equally entranced by a San Francisco butterfly-scape that only got progressively poorer. As Kahn puts it, “We don’t know what we are missing.”
Acknowledging the problem of shifting baselines syndrome, like truly acknowledging the enormity of climate change, can be profoundly disruptive and discouraging. It begs the question of what baseline biologists should be measuring wildlife populations against in the first place. It also can leave us, the public, unsure how to feel about conservation’s supposedly feel-good success stories. In 1973, when the bald eagle was placed on the endangered species list, there were believed to be only 417 nesting pairs of birds left in the lower forty-eight states. In 2007, Fish and Wildlife triumphantly delisted the eagle, having by then built that population up to ten thousand nesting pairs. But the agency also estimates that there may have been as many as fifty thousand pairs in 1782, when the bird became America’s national symbol. And there were doubtless more still when Columbus arrived in 1492, the year often used as a de facto baseline. So do ten thousand eagle pairs represent a miraculous resurrection, or only a meager uptick after a much longer, more devastating decline? Is America flush with eagles? Are we still hopelessly deficient? How many eagles should there be?
In 2005, a paper was published in the journal Nature that sought, in part, to settle this ambiguity. Its lead author was a then graduate student named Josh Donlan. If the problem of shifting baselines was starting to feel unresolvable—like nothing could be objectively measured; like we were staring down into a vertiginous, infinitely receding series of subjective baselines, each invalidated by the one just behind it—then Donlan was ready to bring everyone back onto solid ground.
Once, the paper explained, North America was teeming with spectacular prehistoric megafauna: not just Thomas Jefferson’s mammoths, but shaggy eighteen-foot-long ground
sloths, dire wolves, and beavers the size of bears. There were humongous elk, saber-toothed cats, wild horses, and cheetahs. There were American lions bigger than present-day African lions, and a fleet of meat-eating birds circling overhead, waiting for all these hulking carcasses to drop. Virtually all of these species vanished at the end of the Pleistocene era, about twelve thousand years ago. Why? In part, one hypothesis holds, it was because that was when humans, having arrived in North America over a land bridge from Asia, developed a new kind of stone spear tip called the Clovis point and hunted them to extinction.
Donlan and his colleagues argued that this Pleistocene extinction, and not Columbus’s arrival in 1492, was North America’s zero event—the moment when, ecologically speaking, everything started going wrong. If there was one scientifically defensible baseline for conservationists to agree on, this should be it. That megafauna had tremendous impacts on its ecosystems. Simply trundling around and displacing dirt would have changed the landscape in profound ways, providing habitat for other, smaller critters and insects. The absence of that megafauna has had repercussions, too. For example, it allowed the animals those larger animals ate, like deer and other ungulates, to explode in number, setting in motion a suite of other disorderly consequences.