Vera saw the reserve as an opportunity to test his theory. If geese alone could shape the landscape, what would happen if the animals that inhabited Europe before humans arrived were introduced to the reserve and allowed to graze freely? From within the forest service, he began a campaign to expand the reserve and reroute a planned train track, which would have cut the reserve in half. He won the battle. (“I was committing the two biggest sins in the civil service,” he says now. “I didn’t obey my superiors, and I turned out to be right.”)
The railroad was diverted in 1982, effectively carving out a 15,000-acre wildlife reserve less than 20 miles from Amsterdam. Vera set out to find stand-ins for extinct European grazers like aurochs (ancestral to today’s cows) and wild horses. A year later he introduced 32 Heck cattle, bred by Germans in the 1930s, to approximate the aurochs; a year after that, 20 konik ponies, a Polish-bred version of the wild horses painted on Paleolithic caves, were set free. Forty-four red deer followed in 1992.
Since then the animal populations have exploded. There are now close to 3,000 deer, cattle, and horses living wild in the reserve, which is one of Europe’s largest. The free-roaming herds are not given extra food or shelter during the Dutch winters, which can be cold and long. There are no big predators at the reserve, so more than 20 percent of the large herbivores starve during the winter, numbers that mirror annual deaths at African game reserves.
The decision to let nature take its course initially drew fire from Dutch animal rights activists, who complained that letting horses and cows starve to death was cruel. In a concession to those concerns, rangers now stalk the reserve with high-powered rifles, finishing off animals clearly too weak to survive another week. The carcasses are quickly stripped to the bone by foxes and carrion birds, including the first breeding pair of white-tailed eagles seen in the Netherlands since the Middle Ages.
For Vera it is evidence of a system in balance. The herds have been about the same size for five years, swelling with new calves, foals, and fawns in the spring and shrinking again by winter’s end. When I visit in early May, Hans Breeveld, a wry park ranger with a ruddy beard, takes me for a ride across the polder. The open fields, which are closed to the public, are so closely grazed they remind me of a putting green. “They haven’t been mowed in 12 years,” Breeveld tells me.
As we bounce across the polder, there is constant motion. Flotillas of geese shepherding unruly goslings launch themselves into ponds as we approach. Dozens of cattle stare, then turn and hurry away from the car. The deer are the strangest sight. I’ve seen large groups of cattle before (though usually in stockyards) and small herds of horses at pasture. But I am used to deer as nearly solitary creatures, flitting through the woods in groups of two or three at most. Conventional wisdom holds that three deer per a couple of hundred acres is pushing a forest’s capacity. Oostvaardersplassen’s fields support more than 16 times that many, creating what could be a scene from an old Wild Kingdom special on Africa’s Serengeti: hundreds of red deer bounding in tight herds across the open landscape, turning and running away from Breeveld’s battered green Suzuki 4×4 in unison.
As we drive I borrow Breeveld’s binoculars and stare. Three hours ago I was in central Amsterdam, and now I’m in what looks like a chilly, gray savanna. I ask Breeveld if such huge herds of deer are normal. He looks at me with a slightly mocking smile, as if he is wondering whether I’ve been paying attention for the last few hours. “What is ‘normal’? What’s your reference point? We’ve never let them be in an area this open and large before,” he says.
Oostvaardersplassen is the world’s largest and most advanced exercise in rewilding, but others could soon follow. North America offers some prime settings for another test. Today it is very different from what it was like when humans first arrived some 14,000 years ago. Within a few millennia, the continent lost 59 species weighing more than 100 pounds—from mammoths and horses to lions, saber-toothed tigers, and giant bears.
After decades of focusing on climate as the prime mover in shaping the North American landscape, scientists are increasingly recognizing that animals may have played a major role in shaping their own habitats. Jacquelyn Gill, a University of Wisconsin at Madison paleoecologist, recently used pollen records from an Indiana lake to prove that the disappearance of mammoths and other large herbivores had a major impact on the types of trees that flourished in the region more than 15,000 years ago. Another change: Major wildfires began only after the mammoths were gone, suggesting that the herbivores may have eaten up all of the fire-prone biomass. “We lose so many of our large herbivores, it’s intuitive that the landscape would notice, but the ecological consequences have been largely ignored,” Gill says. “It’s a big question mark as to how much animals were creating and maintaining that habitat.”
Cornell biologist Josh Donlan has proposed running experiments on private land or within nature reserves in the United States to answer that question, using “analogue species” for what he calls Pleistocene rewilding. Elephants from zoos would stand in for mammoths and mastodons, and herds of buffalo and wild horses are already on hand to step back into their Pleistocene places. Donlan has proposed creating protected enclaves similar to Oostvaardersplassen, areas where the impact of large herbivore analogues could be studied. He notes that private game-hunting reserves stocked with everything from gazelles to cheetahs already exist in the American West. So far, though, no one has been willing to let him try. “We pointed to Oostvaardersplassen as a model,” he says. “If Vera can do it in the Netherlands, we can certainly do it in the United States.”
At a remote Siberian research station 100 miles south of the Arctic Ocean, Russian biologist Sergey Zimov is already running a similar experiment. He has been monitoring small herds of moose, horses, and reindeer at what he calls Pleistocene Park for the past 20 years. In 2005 Zimov argued in Science that establishing herds of large herbivores in Siberia might one day change the region’s scrubby, swampy tundra back to the grasslands that once stretched from one side of Eurasia to the other. So far, Zimov is seeing landscape changes similar to what is going on at Oostvaardersplassen.
It may take quite a few of those demonstrations to establish the idea that closed-canopy forests, which most people regard as the normal state of nature, may actually be man-made. In fact, those forests are forbidding places for migrating birds. The forest floor is too barren to support large numbers of grazers, and the canopy is too dense to let light-hungry trees like oaks sprout and grow. They are leafy deserts. Yet traditional forest management usually winds up culling deer and bison—not to mention beavers and boar—when their behavior starts to affect trees. “The tragedy is that biodiversity is sacrificed on the altar of the closed-canopy forest,” Vera says. “There’s this crazy idea that no animals should damage trees, as if trees are made by God not to be eaten.”
Vera, Donlan, and Zimov all say that large animals are the keystones of entire ecosystems. Take them out and things begin to fall apart. Setting the system in motion again, whether with the original species or with modern equivalents, is a boon for biodiversity. Many species flourish on the edges between forests and fields. Ironically, suburban America—landscaped with small stands of trees and wide-open lawns—creates a rough approximation of Vera’s mosaic of forest and field. No wonder there is a plague of deer in America’s backyards.
The day after Breeveld takes me on a tour of the reserve, Vera drives over from his home near Utrecht to explain the science behind Oostvaardersplassen. In the cluttered break room of the ranger station, he pours a cup of coffee and pulls out a map to illustrate his plan to expand the reserve via a corridor to a forest 10 miles away, roughly doubling the area the animals will have access to and opening up forested space.
In 2000 Vera’s doctoral thesis was translated and published in English as Grazing Ecology and Forest History. The book made an immediate splash, dividing the ordinarily sedate field of forest ecology into Vera supporters and everyone else. “It’s the nearest I’ve come to being involved in one of those great Victorian debates,” says Keith Kirby, a forestry expert at Natural England, England’s conservation authority. “Vera is really the first person to develop a coherent alternative to the closed-forest idea.”