This is an article from the March 2010 issue of Discover magazine written by Andrew Curry. The article discusses a reserve in Holland known as Oostvaardersplassen, an area that is being restored to prehistoric conditions.
This is being accomplished by introducing species, or modern equivalents, that roamed the area before humans started drastically altering the surrounding landscape. When it comes to nature and what is “natural,” the current belief is that if you have an area and you do nothing with it, it will turn into a forest, a process known as succession. Oostvaardersplassen is an example that this is not always the case and that we still have plenty to learn about the true state of nature.
[Fran] Vera [the Dutch ecologist who put the reserve into action] says his experiment in rewilding has revealed succession as a human artifact: an unnatural, unbalanced outcome created when people killed off the woolly mammoth and corralled wild horses and cattle. Without free-roaming herds of grazing animals to hold them back, closed-canopy forests took over the land wherever humans did not intervene. The result is a crippled collection of ecosystems that need constant human help to limp along. But Oostvaardersplassen, some 25 years in the making, stands as a test case of what the wild animals that once roamed Europe might create when left to their own devices.
In 1968, Oostvaardersplassen was slated to be an industrial park. By a stroke of luck, the Dutch economy in the early 1970s was in the doldrums. The chemical plants planned for the new land never materialized. Wildlife experts worried that without regular mowing and management, the reeds beds, meadows and marshes supporting such a rich collection of migrating birds would soon give way to bushes and willows. Wait long enough, they predicted, and that growth would in turn give way to dense stands of ash and birch, with the occasional oak managing to push its way through the canopy. In 1978 a few thousand greylag geese landed at Oostvaardersplassen for molting season, the vulnerable spring month when they grow new feathers. The grassy, flat polder was perfect for geese. It had marshy areas for feeding located near open meadows that let geese look out for predators. Within a few years, government experts determined there were an astonishing 60,000 geese molting and breeding at Oostvaardersplassen. They devoured a pound of vegetation a day and stayed for four to six weeks at a time. Everything, from the grass to willow seedlings and reeds, was shorn nearly to the dirt by the ravenous birds.
The more Vera considered that model [succession], the less sense it made. If prehistoric Europe was densely forested, how had meadow-loving geese evolved in the first place, without people mowing to keep their habitat open? How had grazing animals thrived in shadowy, thick woods, let alone evolved to prefer grass? “People argue that animals follow succession; they don’t influence it,” Vera says. “But Oostvaardersplassen shows animals steering the succession.” 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?
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. 44 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% of the large herbivores starve during the winter [...] 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 the same size for five years [...] 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 drive I borrow Breeveld’s binoculars and stare. 3 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.
The hardest part of Vera’s argument to accept is that individual species may come and go, as long as the system stays stable. Oostvaardersplassen suggests that ecosystems are complete only when they need no human help. “Frans has taken more than his fair share of criticism because it is so at odds with some of the conservation philosophy in Europe,” says Kathy Willis, a professor of long-term ecology at Oxford University. “It’s in people’s psychology that they want to manage, and this is very hands-off.”