KoniksImage: Evamariakintzel/Wikimedia Commons

On the train headed north from Amsterdam’s Central Station, be sure to sit to the left. Just past the town of Almere, as you round a right-hand bend, you will find a sight unseen in Europe for centuries, if not millennia: hundreds of red deer, plodding groups of long-horned wild cattle, and skittish herds of low-slung brown horses, all moving through the open landscape like something out of a cave painting. This place goes by the name of Oostvaardersplassen. It is a nature reserve, yes, but it is also a far-reaching experiment. Biologists worldwide are increasingly talking about using large herbivores like the ones sharp-eyed passengers can spot from the train to re-create prehistoric, and sometimes even prehuman, ecosystems.

When keystone species—from ancient mammoths, woolly rhinos, and giant bears to more prosaic grazers like bison, horses, and deer—are wiped out, ecosystems that had sustained themselves in perpetuity collapse. The result is a severe loss of biodiversity. By reintroducing approximations of extinct animals to modern habitats, rewilding advocates want to reestablish dynamic systems that have not existed since the rise of human settlement in Europe. This reserve is the first place where they have done more than talk. Just a short train ride from downtown Amsterdam, nearly 3,000 wild horses, deer, and descendants of prehistoric cattle roam a landscape that is being dramatically shaped by their presence.

The brainchild of a pugnacious Dutch ecologist named Frans Vera, Oostvaardersplassen is challenging some of our most basic assumptions about wildness. Today thick, dense forests are considered synonymous with unspoiled nature. “The current idea is that when you have an area and you do nothing with it, it turns into a forest,” Vera says. Ecologists call this one-way process “succession” and say it rules the unfolding of ecosystems much as natural selection rules evolution. The theory has dominated conservation for centuries, virtually unchallenged.


Until now. Vera 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.

The existence of a prehistoric wilderness in the middle of one of the most densely populated countries in Europe is remarkable in its own right, but Oostvaardersplassen is much more. By forcing ecologists to rethink traditional ideas of hands-on conservation, which focus on micromanaging and preserving species, it heralds the birth of a new model, one in which natural systems work best when they are left alone.

Calling Oostvaardersplassen a “restored” landscape would be totally wrong. Half a century ago, the fields we are chugging across were underneath a vast inland sea. As part of an engineering project to reduce the risk of floods and reclaim land, Dutch authorities essentially created a new province from nothing. Though the engineering challenges are substantial, the principle is simple: Build a dike to wall off the sea, pump out the water to drain the land behind it, let the soil settle, and build. The reclaimed land, called a polder, was once a shipping route in and out of Amsterdam; Oostvaarders­plassen means “lakes of the ones who sail east.” When it was drained in 1968, this area 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. Instead the drained area sprouted reeds and willows—and attracted birds by the tens of thousands, including endangered species rarely seen in the Netherlands. A coalition of Dutch bird-watchers and nature groups pushed, successfully, to set the area aside as a bird refuge.

Wildlife experts worried that without regular mowing and management, the reed 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.

Nature had a surprise in store. 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.

Vera, then a young biologist working for the forest service, read about the winged invasion and began to wonder if the succession model might have a key weakness. In all the traditional models of unmanaged wilderness, the variable was humans; animals were an afterthought. Take people out, the thinking went, and forests will follow. And since dense forests cannot support many large herbivores, large herbivores could never have been very numerous.

The more Vera considered that model, 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.”