It is often compared with the ecosystems of the tropical rainforests, the riverine forest along the Danube at the eastern city limits of Vienna and downstream in Lower Austria, with its rich variety of species and flood plain forest dynamics. Here, more than 600 different species of fern and flowering plants grow, more than 200 species of vertebrates live, including some 50 species of fish. Altogether, biologists have identified some 5,000 species of animals in this nature reserve. Kingfishers breed in remarkably high density in the remains of the backwaters and old river beds. The recently rediscovered Dogfish and the Danube Crested Newt are also of special interest.
This national park area became internationally known because of the threat to its natural beauty from a power plant project in Hainburg, however. In 1984, the construction of a hydro-electric power plant was approved. The felling of trees in the riverine forest near Stopfenreuth in the winter of 1984/85 triggered a wave of resistance. Nobel prize winner Konrad Lorenz and other scientists, as well as numerous politicians, supported the forest squatters. The first success was a stop to the construction work, and a 10-year phase of rethinking finally ended with dismissal of the planning work. The call for donations, "Bail out Nature", by the WWF made a major contribution to this.
The natural water dynamics - both the exchange between river and wetlands through flooding, and the ground water dynamics - are important for the whole ecosystem. Free-flowing water creates the landscape, banks are torn away or eroded by its sheer force, there are accretions in the form of fine sand, but also as gravel banks or islands in other places. Guided tours on foot or by boat give the visitor an impression of this tremendous natural scene.