In 1909, a United States Forest Service officer named Aldo Leopold shot a mother wolf from a perch of rimrock in the Apache National Forest in Arizona. It was a revelatory moment in the life of the young naturalist. “In those days we never heard of passing up a chance to kill a wolf,” Leopold wrote in an essay called “Thinking Like a Mountain,” later included in his Sand County Almanac, published posthumously after his death in 1948 and which went on to sell several million copies. “We reached the old wolf in time to watch a fierce green fire dying in her eyes. I realized then, and have known ever since, that there was something new to me in those eyes—something known only to her and to the mountain.”
Leopold, who today is revered among ecologists, was among the earliest observers of the impact of wolves on deer abundance, and of the impact of too many deer on plant life. In “Thinking Like a Mountain,” he outlined for the first time the basic theory of trophic cascades, which states that top-down predators determine the health of an ecosystem. The theory as presented by Leopold held that the extirpation of wolves and cougars in Arizona, and elsewhere in the West, would result in a booming deer population that would browse unsustainably in the forests of the high country. “I now suspect that just as a deer herd lives in mortal fear of its wolves,” Leopold wrote, “so does a mountain live in mortal fear of its deer.”
One of the areas where Leopold studied deer irruptions was the Kaibab Plateau near the Grand Canyon. By 1924, the deer population on the Kaibab had peaked at 100,000. Then it crashed. During 1924-26, 60 percent of the deer perished due to starvation. Leopold believed this pattern of deer exceeding the carrying capacity of the land would repeat across the U.S. wherever predators had been eliminated as a trophic force. By 1920, wolves and cougars were gone from the ecosystems east of the Mississippi—shot, trapped, poisoned, as human settlement fragmented their habitat— and they were headed toward extirpation in most parts of the American West. Within two generations, the hunting of deer had been heavily regulated, the calls from conservationists had been heeded for deer reintroduction throughout the eastern U.S., and swaths of state and federally managed forest had been protected from any kind of hunting.
Freed both of human and animal predation, however, deer did not follow the pattern predicted by Leopold. Instead of eating themselves out of house and home, they survived—they thrived—by altering their home range to their benefit. As recent studies have shown, certain kinds of grasses and sedges preferred by deer react to over-browsing the way the bluegrass on a suburban lawn reacts to a lawnmower. The grasses grow back faster and healthier, and provide more sustenance for more deer. In short, there has been enough food in our forests, mountains, and grasslands for white-tailed deer in the U.S. to reach unprecedented numbers, about 32 million, more than at any time since record-keeping began.
In 1968, Stanford biology professor Paul Ehrlich predicted that another widespread species would die out as a result of overpopulation. But he was spectacularly wrong. Like the deer, the steadily ingenious Homo sapiens altered its home range—most notably the arable land—to maximize its potential for survival. As Homo sapiens continues to thrive across the planet today, the species might take a moment to find its reflection in the rampant deer.
Conservation biologists who have followed the deer tend to make an unhappy assessment of its progress. They mutter dark thoughts about killing deer, and killing a lot of them. In fact, they already are. In 2011, in the name of conservation, the National Park Service and U.S. Department of Agriculture teamed up with hunters to “harvest” 3 million antlerless deer. I asked Thomas Rooney, one of the nation’s top deer irruption researchers, about the losses in forest ecosystems overrun by deer. “I’d say the word is ‘apocalypse,’ ” Rooney said.
On a warm fall day last year, I went to see Rooney, a professor of biology at Wright State University, in Dayton, Ohio. In his office, I noticed a well-thumbed copy of Ehrlich’s The Population Bomb, and I asked him if he thought a comparison might be drawn between human overpopulation and deer overpopulation. He looked at me as if the point was obvious. “Deer, like humans,” he said, “can come in and eliminate biodiversity, though not to their immediate detriment.” (...)
He told me about a study published last year in Conservation Biology that bemoaned “pandemic deer overabundance,” language suggesting the creature was a disease on the land. Ecosystem damage becomes apparent at roughly 15 deer per square mile, and the damage grows with density. Some areas of the northeast host as many as 100 deer per square mile. (The Wright State University reserve has a density of around 40 deer per square mile.) He noted a 2013 article co-authored by a group of Nature Conservancy scientists who warned that “no other threat to forested habitats is greater at this point in time—not lack of fire, not habitat conversion, not climate change.” (...)
I asked Rooney about the remarkable ability of deer to thrive in their home range—most of the U.S.—while producing ecosystem simplification and a biodiversity crash. In his own studies of deer habitats in Wisconsin, Rooney found that only a few types of grass thrive under a deer-dominant regime. The rest, amounting to around 80 percent of native Wisconsin plant species, had been eradicated. “The 80 percent represent the disappearance of 300 million years of evolutionary history,” he said. He looked deflated.
A turkey vulture pounded its wings through the canopy, and in the darkening sky a military cargo plane howled in descent toward nearby Wright-Paterson Air Force Base. Rooney and I emerged from the forest onto a campus parking lot where Homo sapiens held sway. The self-assured mammals crossed fields of exotic bluegrass under pruned hardwoods surrounded by a sea of concrete, tarmac, glass, and metal. There were no flowers except those managed in beds. There were no other animals to be seen except the occasional squirrel, and these were rat-like, worried, scurrying. The Homo sapiens got into cars that looked the same, on streets that looked the same, and they were headed to domiciles that looked more or less the same. This is home for us.
Leopold, who today is revered among ecologists, was among the earliest observers of the impact of wolves on deer abundance, and of the impact of too many deer on plant life. In “Thinking Like a Mountain,” he outlined for the first time the basic theory of trophic cascades, which states that top-down predators determine the health of an ecosystem. The theory as presented by Leopold held that the extirpation of wolves and cougars in Arizona, and elsewhere in the West, would result in a booming deer population that would browse unsustainably in the forests of the high country. “I now suspect that just as a deer herd lives in mortal fear of its wolves,” Leopold wrote, “so does a mountain live in mortal fear of its deer.”One of the areas where Leopold studied deer irruptions was the Kaibab Plateau near the Grand Canyon. By 1924, the deer population on the Kaibab had peaked at 100,000. Then it crashed. During 1924-26, 60 percent of the deer perished due to starvation. Leopold believed this pattern of deer exceeding the carrying capacity of the land would repeat across the U.S. wherever predators had been eliminated as a trophic force. By 1920, wolves and cougars were gone from the ecosystems east of the Mississippi—shot, trapped, poisoned, as human settlement fragmented their habitat— and they were headed toward extirpation in most parts of the American West. Within two generations, the hunting of deer had been heavily regulated, the calls from conservationists had been heeded for deer reintroduction throughout the eastern U.S., and swaths of state and federally managed forest had been protected from any kind of hunting.
Freed both of human and animal predation, however, deer did not follow the pattern predicted by Leopold. Instead of eating themselves out of house and home, they survived—they thrived—by altering their home range to their benefit. As recent studies have shown, certain kinds of grasses and sedges preferred by deer react to over-browsing the way the bluegrass on a suburban lawn reacts to a lawnmower. The grasses grow back faster and healthier, and provide more sustenance for more deer. In short, there has been enough food in our forests, mountains, and grasslands for white-tailed deer in the U.S. to reach unprecedented numbers, about 32 million, more than at any time since record-keeping began.
In 1968, Stanford biology professor Paul Ehrlich predicted that another widespread species would die out as a result of overpopulation. But he was spectacularly wrong. Like the deer, the steadily ingenious Homo sapiens altered its home range—most notably the arable land—to maximize its potential for survival. As Homo sapiens continues to thrive across the planet today, the species might take a moment to find its reflection in the rampant deer.
Conservation biologists who have followed the deer tend to make an unhappy assessment of its progress. They mutter dark thoughts about killing deer, and killing a lot of them. In fact, they already are. In 2011, in the name of conservation, the National Park Service and U.S. Department of Agriculture teamed up with hunters to “harvest” 3 million antlerless deer. I asked Thomas Rooney, one of the nation’s top deer irruption researchers, about the losses in forest ecosystems overrun by deer. “I’d say the word is ‘apocalypse,’ ” Rooney said.
On a warm fall day last year, I went to see Rooney, a professor of biology at Wright State University, in Dayton, Ohio. In his office, I noticed a well-thumbed copy of Ehrlich’s The Population Bomb, and I asked him if he thought a comparison might be drawn between human overpopulation and deer overpopulation. He looked at me as if the point was obvious. “Deer, like humans,” he said, “can come in and eliminate biodiversity, though not to their immediate detriment.” (...)
He told me about a study published last year in Conservation Biology that bemoaned “pandemic deer overabundance,” language suggesting the creature was a disease on the land. Ecosystem damage becomes apparent at roughly 15 deer per square mile, and the damage grows with density. Some areas of the northeast host as many as 100 deer per square mile. (The Wright State University reserve has a density of around 40 deer per square mile.) He noted a 2013 article co-authored by a group of Nature Conservancy scientists who warned that “no other threat to forested habitats is greater at this point in time—not lack of fire, not habitat conversion, not climate change.” (...)
I asked Rooney about the remarkable ability of deer to thrive in their home range—most of the U.S.—while producing ecosystem simplification and a biodiversity crash. In his own studies of deer habitats in Wisconsin, Rooney found that only a few types of grass thrive under a deer-dominant regime. The rest, amounting to around 80 percent of native Wisconsin plant species, had been eradicated. “The 80 percent represent the disappearance of 300 million years of evolutionary history,” he said. He looked deflated.
A turkey vulture pounded its wings through the canopy, and in the darkening sky a military cargo plane howled in descent toward nearby Wright-Paterson Air Force Base. Rooney and I emerged from the forest onto a campus parking lot where Homo sapiens held sway. The self-assured mammals crossed fields of exotic bluegrass under pruned hardwoods surrounded by a sea of concrete, tarmac, glass, and metal. There were no flowers except those managed in beds. There were no other animals to be seen except the occasional squirrel, and these were rat-like, worried, scurrying. The Homo sapiens got into cars that looked the same, on streets that looked the same, and they were headed to domiciles that looked more or less the same. This is home for us.
by Christopher Ketcham, Nautilus | Read more:
Image: Chris Buzelli
