In the 1980s, Dutch ecologists released cattle, horses, and deer into a fenced polder to recreate “wild Europe”; in one winter, its herds collapsed

"The road to hell is paved with good intentions.” Netherlands’ Oostvaardersplassen is perhaps best summed up in that proverb. In the 1980s, ecologists in Flevoland, Netherlands, embarked on an ambitious new project endorsed by the government: the possibility of rewinding Europe's ecological clock. They set hardy cattle, horses first, followed by deer in the 1990s, to roam free in a fenced landscape as nature took its course with no supplemental feeding or human disturbance.

The experiment was long seen as a conservation success, until harsh winters brought dwindling herds, starving animals and public outcry. According to historian Bert Theunissen in his 2019 paper “The Oostvaardersplassen Fiasco,” published in the journal Isis, the project failed not only because of its ecological consequences, but also because of its underlying moral and philosophical conflicts between the ideals of wilderness held by the scientists and the moral view of human responsibilities, as embraced by society. Today Oostvaardersplassen is often cited as a cautionary tale in conservation.

A wilderness built from scratch


Unlike Yellowstone or Yosemite, Oostvaardersplassen wasn't one of the ripe places for wilderness preservation. It was engineered to be one. The reserve is located in reclaimed land, that is, in a polder formed by draining part of the IJsselmeer. According to The Oostvaardersplassen Fiasco, it was unfit for farming, and therefore, naturally became wetlands, which quickly began to attract remarkable birdlife.

Conservationists brought in Heck cattle, Konik horses and red deer, as an inspiration from Dutch biologist Frans Vera, who believed that prehistoric Europe was a mosaic of grazing grasslands, rather than a continuous forest. They were not aurochs or wild horses, but ecological substitutes to perform similar functions.

When success looked too good

The experiment appeared to be an outstanding success for many years. Rare birds returned. Wetlands flourished. The reserve was internationally recognised and added to the European Union's Natura 2000 network of protected areas. In the absence of predators, however, populations of the herbivores proliferated.

At first this was far from a failure; rather, a proof that the natural processes were being fulfilled. Ecologists thought that seasonal food shortages would help control populations, as wolves and other predators once did. In theory, it all made sense. Unfortunately, reality can be very different.

Nature without predators isn't quite nature

There are referees in every ecosystem that you can't see. Generally, in functioning wildernesses, a predator dictates where herbivores will graze, how long they will stay, and the rate of their population growth. Oostvaardersplassen had no such checkpoints. The reserve was also closed off with fences.

The animals were unable to migrate like other wild animals would in a natural way when there is a shortage of food during the winter season. Nor was there any predator to keep numbers down before they began to dwindle. As a result, however, starvation became the chief method of population control. A 2018 Roots of Nature article subsequently saw this missing ecological process as one of the largest weaknesses of the experiment. The herbivores were reintroduced, but there were no forces that historically would have kept them balanced.

Nature on trial

But then came the winters, and all of it took a drastic turn. The cattle were starving due to severe winters; first in 2005, and then the one that occurred in 2017-2018, which Bert Theunissen referred to as a “carnage.” Newspaper coverage, TV, and social media flooded with graphic images. Despite official restrictions, protesters went in to feed weakened animals, and protests were held throughout the Netherlands, as reported in BBC News.

Everything changed when the question of science turned into a moral one: Is it okay for humans to interfere, after deliberately introducing animals into an enclosed landscape? Theunissen believes that many never came to terms with the fact that the animals were "wild.” The idea of them being under the control of humans, and not part of an undisturbed ecosystem, stuck in the public image, because they were fenced off and precluded from migrating.

The myth of "perfect balance”

The debate showed that it was more than a botched conservation effort. Theunissen stated that people, both for and against, have tended to use, deliberately or not, this longstanding assumption that nature strives to be in perfect balance. However, modern ecology has seen ecosystems as dynamic as opposed to stationary entities.

Perhaps more than biology itself, expectations of an ideal self-regulating wilderness led to the controversy. Utrecht University also found that ecological science was not solely responsible for the collapse, but also communication failures, public values, and management decisions.

Lessons beyond the Netherlands

A staggering public outcry over this led to a change in the Dutch one-size-fits-all management system. According to The Guardian, the concept of a fully self-regulating reserve was scrapped, and thousands of deer are now subjects of regular culling for population reduction. Oostvaardersplassen is still a biologically important wetland today, despite the change in its legacy.

Instead of demonstrating the failure of rewilding, a lot of conservation scientists stand to argue that rewilding must take responsibility for complete ecological systems: predators, migration corridors, landscape connectivity and, above all, public trust. The Rewilding Institute calls the debate a "moral greylag zone," where scientific ambitions and societal ethics inevitably intersect.

Oostvaardersplassen is a troubling but helpful reminder as discussions over wolves, bison and large-scale restoration continue in countries like the United States. Nature can be astonishingly resilient. Human guesswork about nature is often far less so.