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Kindle Notes & Highlights
by
Ben Goldfarb
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January 28 - February 8, 2024
Sometime during the twentieth century, scientists have written, roadkill surpassed hunting as “the leading direct human cause of vertebrate mortality on land.” Name your environmental ill—dams, poaching, megafires—and consider that roads kill more creatures with less fanfare than any of them.
Inspired by inattention, Forman soon coined an English term: road ecology, defined loosely as the study of how “life change[s] for plants and animals with a road and traffic nearby.”*
The goal of Yellowstone to Yukon, or Y2Y, is boggling: its advocates envision a network of connected habitats that would permit animals to wander unhindered along the spine of the Rockies, a region that spans five American states and four Canadian provinces and territories.
The mission of Y2Y and its many partners was to plug those holes, to help bears and other animals safely navigate the Rockies without running afoul of humans.
How does a moose comprehend traffic? What sort of tunnel appeals to a mink? Why do grizzly bears prefer crossing over highways while black bears go under?
Cars hijacked their victims’ own biology, subverting evolutionary history and rendering it maladaptive.
Cars have made deer North America’s most dangerous wild animal, implicated in three times more deaths than wasps and bees, forty times more than snakes, and four hundred times more than sharks.
Mostly, though, early road ecologists didn’t find roadkilled deer for one reason: there weren’t deer to kill.
For all its gifts—its acute senses of hearing and smell, its leaping prowess, its four-chambered stomach—the whitetail’s greatest aptitude was its ability to live cheek-to-antler with people, to flourish in the rectilinear hash we made of once-fluid landscapes.
In 2016 a biologist named Sandra Jacobson and her colleagues split animals into four categories based on how they react to roads. On one end of the spectrum were the nonresponders, creatures that ignore roads at their peril—like leopard frogs, which hop across roads no matter the traffic—and pausers like porcupines and skunks, which creep onto highways and then hunker down. On the other end sat wary, intelligent avoiders, such as grizzly bears, who generally steer clear of even rural roads. Whereas nonresponders are fatally heedless, avoiders are imprisoned by their own innate caution.
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A lonesome county road could thus have the same negligible deerkill as an interstate: the former because it’s traveled by so few cars that deer easily speed between them; the latter because traffic’s moving fence is so densely woven that they don’t even try.
Fences kept ungulates off the interstate. Underpasses got them across it.
The concrete culvert that Eddins installed at Nugget Canyon was superficially similar to the original I-80 passages, but it had a far higher openness ratio. Eddins’s underpass was twice as wide—twenty feet instead of ten—and much shorter; a deer standing at one end could see clear to daylight on the other.
The average DVC, they calculated, set society back $6,600. Bigger animals inflicted worse damage: elk collisions cost $17,500, while moose came in at a whopping $31,000.§ All told, animal crashes were costing America more than $8 billion per year.
Nugget Canyon underpasses, which prevented ninety-five crashes annually, paid for themselves within five years.
As wildlife crossings caught on, a geographical rift cleaved America’s transportation departments. Western mule deer and elk migrated so faithfully that they formed unmistakable roadkill hotspots.
Meanwhile, eastern states continued to struggle with their old nemesis: white-tailed deer. Unlike muleys, whitetails didn’t migrate along consistent routes; instead, they seemed omnipresent.
But Donaldson refused to surrender. Virginia’s whitetails didn’t migrate, true, but they did use certain predictable habitats, like stream corridors and woodland edges.
In Switzerland roads distorted the genes of species from roe deer to bank voles; in the Mojave Desert they pared the genetic diversity of bighorn sheep. In the Northern Rockies grizzly populations are so disunited by highways that researchers can tell, from the merest snippet of DNA, on which side of which road any bear was born. Abax parallelepipedus, a flightless European beetle, disperses so feebly that biologists once found a genetically distinct population encircled by a highway exit loop.
The freeway forced a turf war that favored entrenched animals over low-caste nomads and skewed genes on both sides. Coyotes north of the 101, Riley found, were so distantly related to southsiders that they might as well have lived hundreds of miles apart.
Clevenger and a biologist named Mike Sawaya stretched threads of barbed wire across the entrances to Banff’s passages, which snagged the fur of any grizz who squeezed past. “With a bit of hair, it’s like leaving a pad and pencil,” Clevenger said. “And every individual that comes through writes down their species, their sex, who their mother and father is, and where they came from.”
Like pronghorn, grizzlies preferred bridges to underpasses, a choice rooted in their past: whereas black bears are forest creatures who tolerate tight spaces, grizzlies were historically plains dwellers who overwhelm their opponents with power and speed in the open. All-important females, especially sows with cubs, particularly favored overpasses, whose sightlines allowed them to watch out for infanticidal males. Overpasses were thus the most “family-friendly” structures, capable of transporting bears regardless of age or sex.
from extinction’s door. As a result, roadkill is an overlooked culprit in our planet’s current mass die-off, the sixth major extinction in its history.
Since 1970 the world’s animal populations have dwindled by an average of 60 percent; pull back to 1900, and a third of our vertebrates have declined in numbers and range.
Around one in five reptile species and two in five amphibians are endangered, and many more are on their way.
The forces muzzling the frogs are many—habitat loss, fungal disease, pollution—but it’s not coincidence that herps are predisposed to become roadkill. Reptiles and amphibians move slowly and, being cold-blooded, gravitate toward warm surfaces, whether limestone or asphalt. They’re surprisingly wide-ranging: turtles lumber across lakefront streets to deposit their eggs; snakes slither over highways to huddle in hibernacula. Worst of all, most herps aren’t speeders like deer or avoiders like grizzlies. Instead, they’re nonresponders: animals who are unfazed by traffic, even when prudence would
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You’ve probably never heard one pop beneath your tires, but in many places it’s herps—not deer, not squirrels—that make up most vertebrate roadkill.
Many biologists concurred. Roadkill was widely considered “compensatory mortality,” a form of death balanced by the scales of life. If more frogs were flattened, the thinking went, maybe fewer would get eaten by predators, or there would be more food for their tadpoles.
Roadkill was not exclusively a source of compensatory mortality: it could also be additive mortality, death that never came out in nature’s wash.
Wild ecosystems weed out the sick and the old—the diseased fawn devoured by wolves, the senescent moose who collapses in a snowdrift. Roadkill, by contrast, is an equal-opportunity predator, as apt to eliminate the strong as the feeble.
Langton began to look into toad tunnels: miniature underpasses, between ten and eighteen inches in diameter, that had first been installed in Switzerland and later proliferated in Germany.
Tunnel design mattered, too. Because air didn’t readily circulate through small passages, tunnels often developed the cool, dry microclimate of a wine cellar. Amphibians, however, preferred conditions warm and damp, more like a sauna. Biologists rectified the problem by building larger tunnels with open grates that permitted the entry of light and water.
Even a 3 percent increase in additive mortality, a few crushed elders each year, can send turtle populations into a tailspin.
As time wore on, Aresco noticed another troubling trend: turtle-kill discriminated between sexes. Chelonian society is marked by an unequal division of labor. During nesting season males loaf in the pond, while females heave themselves overland in search of egg-laying sites, including sandy roadside soils.
By 2005 more than five hundred road miles had been expunged from the Clearwater’s network.
Decommissioning just 1 percent of Forest Service roads each year for a quarter-century, scientists have calculated, would increase wildlife habitat by around 25 percent.
And the Phantom Road didn’t merely drive off birds: it drained those who stayed. When Carlisle captured warblers and examined their tiny bodies, she found they were skinnier after they’d been near the Phantom Road.
Like most animal collapses, the insect apocalypse starts with habitat loss. That’s particularly true in the Midwest, where more than 99 percent of historic tallgrass prairie has been sacrificed to agriculture and development.
Humans have always coveted salt, a commodity so precious that Roman soldiers were paid in it, the etymology of salary.
Road salt (principally chloride) slows trout growth, makes frogs more susceptible to viruses, and ferments dead zones. Like greenhouse gases, which will heat our planet long after we’ve stopped emitting them, sodium chloride is a legacy pollutant that outlives the snowplow driver who applied it.
Slater once watched eagles pick at a pronghorn in a field for hours, nursing their repast like day-drinkers in a pub. Put that pronghorn beside a highway, though, and the birds get jittery. Slater’s team found that golden eagles spend an average of just nine minutes on a roadside carcass at a time, and “flush”—birdspeak for fly away—every fifth car, a tendency that leads them into the paths of passing trucks.
Deadliest of all, though no one knew it then, were the particulates shed by tires. Scientists would eventually pin decades of coho salmon die-offs on 6PPD-quinone, a chemical that manufacturers apply to tires to protect them from ozone. We’d paved the earth for cars, then used them to poison it.
Brazil’s biodiversity and its roads both invite superlatives: it hosts the world’s most amphibians, the most freshwater fish, the second-most mammals, the third-most reptiles, and the fourth-longest road network. (It trails only the United States, China, and India.)
“I’m, uh, not very fast,” I said. Alves wouldn’t let me off. “You don’t need to be fast. You must be like a hobbit. Very quiet,” he said.
A single anteater pup gestates for six months, then clings for another six to his mother, splayed across her back like a saddle.
Today, roadbuilding and land-clearing, the Amazon’s scourges, still move in lockstep. Ninety-five percent of deforestation occurs near roads and rivers, and more than a third of the forest is considered “highly accessible.”
Brazil is one of many countries being remade by Chinese investment. In 2013 China launched the Belt and Road Initiative (BRI), an incomprehensibly vast welter of highways, railroads, shipping lanes, power lines, and other linkages that would bind about seventy countries in Asia, Africa, Europe, and South America—the largest construction project in human history.
Practically every highway I’d ever driven on, I realized, was built to facilitate swift and seamless automobility. SP-139, by contrast, deliberately transgressed the conventional ideals of engineering, frustrating human users in service to wild animals.
