When the plans for South Flevoland were made, the planners were not only thinking of people. A 6,000 hectare piece of marshland on the edge of the polder was reserved as a nature area. Hundreds of species of bird, including geese, cormorants and spoonbills, have made the Oostvaardersplassen their home. Highland cattle, wild horses and deer were brought in to keep the undergrowth down.