Post-Atta
The result was what came to be unfondly known by the Guri researchers as the post-Atta stage. The forest post-Atta was a depressing place where the leafiest, tastiest trees had been progressively replaced by walls of defensive vines and thickets of the thorniest, least-palatable plants of the forest, a place even the birds had abandoned. “It is one of the nastiest places you can imagine,” said Ken Feeley, one of Terborgh’s students and chief investigators on Guri. Feeley shuddered to remember the nastiest post-Atta island of all, an island the crew came to name Sudor, Spanish for “sweat.” “We would go in with machetes, and we wouldn’t know which way to turn,” recalled Feeley. “There were more thorns than I ever thought possible. They’re terrible places, the post-Atta forests. I don’t know how else to describe them.”
Feeley later came to learn that his predecessors had given Sudor a nickname of their own. They had called the island Difícil, Spanish for “difficult.”
As the lianas gained control, they spread atop the canopies, blocking the light, smothering the trees. The seedlings and saplings of the Guri forests were dying faster than they could be replaced. No more monkeys, no more ants, no more trees. “The end point of this process,” Terborgh and his colleagues would later write, “is a nearly treeless island buried under an impenetrable tangle of liana stems.”
Said Feeley, “I wish everyone could go to Guri. Because I think our message would be crystal clear then, if they were actually able to see this place.”
In the contorted kingdom of Lago Guri, Terborgh and crew had come to witness the green world hypothesis of Hairston, Smith, and Slobodkin turned upside down. “If you had any doubts about top-down regulation before,” said Terborgh, “all you have to do is see a system regulated from the bottom-up. Once you’ve seen it, you realize you’ve never seen anything like this before.”
Brown New World
In 2001, Terborgh and ten colleagues published the most famous of their dispatches from Guri, a Science paper titled, with Terborghian flare, “Ecological Meltdown in Predator-Free Forest Fragments.”
“These observations are warnings,” wrote Terborgh and his coauthors, “because the large predators that impose top-down regulation have been extirpated from most of the continental United States and indeed, much of Earth’s terrestrial realm.”
Under Terborgh’s meltdown scenario, the grim cascade that had dismantled the little islands of Guri—the initial free-for-all of the herbivores, the collapse of howler monkey society, the pillaging of forests by the ants, the smothering shrouds of thorny vines—was the green world gone brown.
Look around, Terborgh implored. Look at the overgrazed grasslands of the arid American West, giving way to prickly scrub and thorn; look at the forests of Malaysia disappearing under assault by wild pigs, or those of the eastern United States being swallowed by white-tailed deer.
If Lago Guri was any indication, the inverse of a world ordinarily kept green by predators was not a pretty place to ponder. And one of those places, dearest to heart, happened to be Terborgh’s own boyhood backyard.
SIX
Bambi’s Revenge
IN 2003, NEARLY A decade into documenting Guri’s decay, Terborgh’s study came to an inglorious end. A prolonged Venezuelan drought had drawn down the lake waters, exposing land bridges that turned the archipelago into a muddy amorphous mass. The miserable howler monkeys fled their prisons. The great experiment was over. But not before its images of ecological meltdown had been stamped into the conscience of conservation biology.
A year later, while taking a break from business meetings in Washington, D.C., Terborgh ventured a sentimental journey to the forested banks of the Potomac, to the baptismal parks of the boy naturalist. The sixty-nine-year-old Terborgh came away crestfallen. The wildflower garden of his youth had become a wasteland of foreign weeds. A forest floor once colored with bluebell, phlox, and spring beauty had been swept by an invasion of garlic mustard and Japanese stilt grass.
Thousands of miles and an ecological universe apart from Venezuela, Terborgh could not escape the specter of Lago Guri. “It looks like a war going on out there,” he said. “That big tract of forest was eaten down to the ground. The whole character of it—it’s just a ghost of what it was. And it’s all deer.”
Planet of the Deer
Terborgh had not just happened upon a rough spot in the woods, some bad stretch of scenery. He could have been dropped into almost any green space of the Capital region and come away with the same verdict. He could have looked into Rock Creek Park, the majestic forested corridor running so incongruously jade through the heart of D.C., and found the forest bereft of seedlings and overrun with unpalatable weeds. Mason Neck National Wildlife Refuge to the south and Bull Run and Riverbend parks to the west were besieged by deer herds as many as forty times thicker than what their attending biologists believed the forests could sustain.
Terborgh could have kept going, to the national parks of Catoctin in Maryland, to the Shenandoah of Virginia, the Great Smoky Mountains of Tennessee, all the way to Rocky Mountain National Park of Colorado, and found unhindered herds of deer and elk harvesting future generations of forest. He could have visited researchers in the field, somberly linking the burgeoning herds to disappearing life-forms, orchids to insects, red cedars to black bears. He could have crossed the Atlantic or the Pacific, northern hemisphere or southern, western Europe, Asia, New Zealand, Japan, to find the deer booming and woodlands withering. The family of deer—white-tailed or black-tailed, Sitka deer, fallow deer, roe deer, mule deer, elk or moose—had come to dominate food chains across the temperate latitudes.
It did not take an ecologist to spot the symptoms. Epidemiologists were pointing to North America’s suburban epidemic of Lyme disease, a neurological infliction carried by a blood-sipping arthropod hosted by deer. Vehicular crash statisticians had been morbidly charting the rising tallies of deer flying through windshields and death on the highways. Cultural historians overseeing the battlefields of Gettysburg, Antietam, and Manassas were losing their battle to keep fields and forests of the Civil War’s landscape from being eaten beyond recognition. And practically any gardener within foraging distance of the suburban deer could tell you that their war was already lost.
Terborgh’s “all deer” hyperbole wasn’t too far off. The mainland had, in effect, been Guri-ized, portioned into bite-size pieces, barred of big predators, and groomed for a takeover by the generalist masses. For the white-tailed deer in particular—given the hard times the species had endured in its evolutionary past—the twenty-first century had dawned as one immense rose garden.
Making of the Monster
The Pliocene epoch, in which the white-tailed deer arose three to four million years ago, was a tumultuous period of global cooling and drying rocked by pivotal spurts of tectonics. It came with the uplifting of ranges—the Cascades, Rockies, and Sierra Nevada—wringing moisture from the westerly winds, drying the plains in their lee, and cultivating the steppes and savannas on which the deer and most of the continent’s modern hoofed animals evolved.
Two million years of Pleistocene ice ages followed, along with their emblematic mammoths and mastodons, giant ground sloths and saber-toothed cats. The Pleistocene was a time of mammalian giants, with five times as many kinds of large herbivores as today and twice as many forms of big predators chasing them. And through that gauntlet of Goliaths slipped a wispy, twig-nibbling deer.
Odocoileus virginianus, the white-tailed deer, was an opportunistic, weedy sort of creature, surviving, as one evolutionary biologist has put it, “between the cracks” of more specialized species. It assumed the role of the consummate generalist, a cosmopolitan herbivore of the grasses, buds, flowers, spores, and fruits, sampling widely across the kingdoms of plant and fungi. A deer well fed and unfettered by predators was an inherently fecund animal, capable of producing a fawn in its first year of life, and twins, triplets, and even quadruplets in its prime. On good range, a whitetail h
erd could double itself in two years.
Prospering in the Pleistocene commonly entailed escaping. The winter hide of the deer was the tawny gray of tree bark, its summer-slim profile melting through green walls of brush. Ever-twitching ears and vigilant eyes were backed by athletic getaway skills. On long thin limbs, levered all the way to its toenail hooves, the whitetail could spring away at forty miles per hour, leaping eight-foot shrubs and treefalls in the way. The deer guru Valerius Geist has watched whitetails turn and outrun his rocket-propelled capture nets fired from forty feet, and nonchalantly dodge arrows traveling seventy yards a second.
When hiding and fleeing failed, the cornered deer was equipped to fight, striking with sharp hooves and horns. Deer have been known to kill wolves, and cougars have been found dead with vital organs punctured by antlers.
Beyond surviving the Pleistocene, the white-tailed deer exploited it. The species spread from the Arctic Circle to sub-equatorial Peru. It spun off a new line of deer along the way, an open-ground version suited to the arid West, named Odocoileus hemionus, the mule deer. By the time Europeans arrived in North America five hundred years ago, some twenty-four to thirty-three million deer populated the continent (an admittedly tenuous estimate offered by the historians Thomas McCabe and Richard McCabe). And that is when the trajectories went haywire.
The Fall and Rise
Over the next three centuries, with settlers and Indians slaughtering deer for hides and trade, the deer numbers dipped. After which they plummeted. In the latter half of the 1800s—in the same half-century spree of market hunting and mindless gunning that brought the American bison from tens of millions to a few dozen individuals; that brought the passenger pigeon from billions to extinction—the whitetails of North America were eradicated over vast reaches of the expanding American empire. One Virginian, among many examples, took credit for killing more than 2,700 whitetails himself. McCabe and McCabe characterized the era’s carnage as the greatest hunting pressure on wildlife ever.
Which was followed by one of the greatest wildlife comebacks ever. Market hunting was outlawed. States that had exterminated their deer began restocking, and pampering their returning natives. Foresters, farmers, and suburban architects cut swaths through the deep forest, laying open a landscape of fresh forage. Professional predator-killers vanquished the deer’s enemies. By the mid-1900s the only wolves remaining south of Canada were rumored bands of renegades. Cougars in the East had been driven from all but a tiny pocket in the Florida cypress swamps, while those in the West harried to the wildest of hideouts. Even the human predator had been hamstrung—by choice. Deer seasons were shortened, bag limits were reduced, does were declared off-limits. The deer’s American buffet was open 24-7, no predators allowed.
By the time Terborgh revisited his boyhood home at the start of the twenty-first century, the deer that he recalled hardly ever seeing in all his younger trampings about the Virginia woods were swarming like ants on an armadillo-free island in Venezuela. To many hunters and wildlife professionals, the crowded forest was an American success story. For those with broader concerns for such things as flowers and birds and future generations of forests, the deer resembled more the apocryphal fire bearing down on a sleeping village.
Leopold
One of the first to raise the alarm was the same man who had helped light the tinder. In 1933, a University of Wisconsin wildlife professor named Aldo Leopold authored Game Management, the first textbook dedicated to managing and restoring wildlife populations. Still a cornerstone in the field, Game Management pivots on the philosophy that “the way to manage game is to manage habitat.” And the way to manage deer is to clear.
With his disciples storming the woods with their saws, the father of wildlife management began to suffer second thoughts. Those well-lit gaps with their flushes of green food had indeed stoked the herds’ reproductive engines as planned. Though with the herds’ predators now gone, nobody had given enough thought as to how to turn them off. All that energy streaming from the sun, much of which had once gone toward growing the forest’s next generation, was now channeling into the bellies and biomass of the burgeoning deer herds.
Invited to Germany in 1935, Leopold toured the country’s forests, meticulously managed for maximum timber and game. To Leopold, there was something eerie about the German superforests, something bleak in their factory productions. The images reminded him of a dark Devonian forest from the predawn of the dinosaurs. There was spruce in the canopy, ferns on the ground, and little else in between. He wrote, “One cannot travel many days in the German forests, either public or private, without being overwhelmed by the fact that artificialized game management and artificialized forestry tend to destroy each other.”
Leopold returned to the States a changed man. He had seen in the sterility of the German woods a harbinger of the Wisconsin forest. From his chair as a Wisconsin conservation commissioner, Leopold became the forest’s spokesman, campaigning for more deer hunters and mercy bullets, in lieu of stripped forests and slow death by starvation. Leopold even ventured an olive branch to the timber wolf and mountain lion, the same vermin whose exterminations he had once championed as a brash tender-foot forester. He warned that Wisconsin was heading toward a bitter end, “with impoverished herds, depleted forests, and (I hope) a fund of painful experience.”
Time and again Leopold’s message was shouted down by mobs of hunters and their politicians, teeth bared in defense of the swelling herds. Leopold died in 1948, with the game farmers in power and the deer herds on moonward trajectories. But he had by then sown the seeds of resistance. He had started his students and their students thinking more deeply about the forests as something other than feedlots for white-tailed deer.
“Dandelions Are Nice”
In 1985, three botany students at the University of Wisconsin-Madison got together over home-baked chicken cacciatore and a fresh draft of Wisconsin’s new forest-management plan. The three had just finished several seasons in the woods, surveying rare plants throughout northern Wisconsin. What the U.S. Forest Service was proposing for those woods struck the young botanists as lunacy. The feds were planning more clear-cuts, to harvest more timber, to grow more deer. Everything the botanists had seen suggested that more deer were the last thing the forests of Wisconsin needed.
In their forays they had so often come upon the beheaded stems of lady’s slipper orchids and trillium lilies, growing ever more rare in forests as sterile as city parks. They were astonished, by way of contrast, by the flourishing forests they found on the Menominee Indian Reservation—where liberal hunting seasons had kept the deer herd trimmed to a fraction of those found in the national forests. The cedars of the reservation were like none they had ever seen. “Since I was a kid, I had always thought of cedar swamps as being these beautiful parklike things where the understory is really clear, where you could see a long ways, where you could spot orchids thirty or forty feet away,” said the botanist William Alverson. “And I got into the Menominee and realized I couldn’t see more than five feet. It was because of the cedar regenerating. I said, ‘Holy crap, this is what a cedar swamp is supposed to look like!’”
Alverson and colleague Stephen Solheim enlisted Solheim’s adviser, Donald Waller, to their cause. Waller was a botany professor, otherwise busy at that time “investigating uncontroversial topics like why plants have sex.” Years earlier, as a graduate student at Princeton, Waller and his botany professor John Terborgh had conducted a study just outside the D.C. Beltway, in a park near Terborgh’s boyhood home. They counted as many as two dozen species of native flowering plants in a single square meter of forest floor along the Potomac. The same abundant forest that had sensitized Terborgh’s eye to the decay that followed had served Waller’s as well. “I mean, here we were in the land of Leopold,” said Waller. “Here we were beginning to see the dramatic effects of deer in the woods, and nobody in wildlife ecology, nobody in the Division of Natural Resources, was researching any of this.”
<
br /> After the foresters blithely waved away the botanists’ recommendations, the botanists went public. Their resulting paper, “Forests Too Deer: Edge Effects in Northern Wisconsin,” appearing in a 1988 issue of the new journal Conservation Biology, served as both a warning to their colleagues and a bald indictment of the deer managers. The three buttressed their own observations in the Wisconsin woods with evidence marshaled from across the scientific literature, citing studies from Nebraska to Pennsylvania to Long Island. Missing species, failing forests, outbreaks of Lyme disease—all came under one suspicious shadow of supersaturated densities of deer. Stewards of rare orchids had to cage their plants against the swarms. Commercial foresters in Pennsylvania had resorted to fencing off their stands as a pre-requisite for growing new timber. And the U.S. Forest Service was prescribing more deer?
In the year following publication of “Forests Too Deer,” the authors received upward of a thousand requests for reprints. Few of them came from the deer managers. “I was told at the time that we were being alarmist,” said Waller. “I was told the problems were local, temporary, that it’s only a matter of time before a harsh winter would knock back the deer population, or that the hemlock wasn’t regenerating because of climate change. Whatever.”
Where the Wild Things Were Page 12