Before the establishment of the reserve, the dry area was a nursery for willow trees, and in the first year hundreds of seedlings could be found on each square meter. This led to concern that a dense woodland would develop, significantly reducing the value of the habitat for water birds. To avoid this, the park's managers brought in a number of large herbivores to keep the area more open, including Konik ponies, red deer and Heck cattle.
Before they were driven to extinction, large herbivores in this part of Europe included the tarpan (wild horse), wisent (European bison), red deer (elk or wapiti in North America) and aurochs (wild cattle). The tarpan and aurochs are extinct, but Konik ponies and Heck cattle are able to act as functional equivalents, occupying a similar ecological niche.