A Pleistocene Park on a Polder
The Oostvaardersplassen is a 5,600-hectare nature reserve with an unusual origin story. The land it occupies did not exist until 1968, when the South Flevoland polder was reclaimed from the sea. Initially slated for industrial development, the plan was abandoned, and nature quickly colonized the new, fertile soil. The area developed into a wetland that became a bird sanctuary, especially greylag geese.
In the 1980s, Dutch ecologist Frans Vera proposed a novel idea: use large herbivores to create and maintain a dynamic, half-open area resembling what he theorized existed in Europe during the Pleistocene epoch. The goal was to establish a self-regulating ecosystem with minimal human interference. To achieve this, several species were introduced as proxies for extinct megafauna. Heck cattle (Bos primigenius taurus) were brought in as stand-ins for the aurochs, and Konik horses (Equus ferus caballus) for the wild tarpan. These were later joined by red deer (Cervus elaphus) in the 1990s.
The initial results were promising. The grazing animals shaped the area, preventing it from turning into a dense forest and creating a mosaic of habitats. The reserve became an internationally recognized bird sanctuary, part of the Natura 2000 network, and the site of the first breeding pair of white-tailed sea eagles (Haliaeetus albicilla) in the Netherlands since the Middle Ages.
An Experiment in Crisis
The hands-off management approach led to a predictable and severe problem. Without natural predators to control their numbers, the populations of deer, horses, and cattle grew exponentially. After a series of mild winters, the combined population peaked at over 5,200 animals by the end of 2017. The ecosystem could not support this density.
During the harsh winter of 2017-2018, a massive die-off occurred. Over 3,200 animals died from starvation or were culled by park rangers to prevent further suffering. This event, visible to passengers on the railway line bordering the reserve, sparked widespread public outrage. Protesters gathered at the fences, comparing the reserve to Auschwitz, and some activists illegally threw hay over the barriers to feed the starving animals.
The controversy forced a complete policy reversal. In 2018, the provincial authority of Flevoland took control and ended the non-intervention experiment. A new management plan was implemented, capping the total number of large grazers at around 1,100 animals. This population is now maintained through systematic culling and relocating animals to other reserves in Spain and Belarus. The policy of allowing nature to run its course, including mass starvation events, was officially abandoned.