Before the closure of the Haringvliet, it was a large nature reserve. As was recently stated, the Haringvliet became a lake after the construction of the Haringvliet dam. The soil which was flooded during high tide was uncovered and was used by farmers. Consequently, many geese lost their habitat area.

The tide change no longer influenced the flora and fauna. Many plants and animals that depended on the sea, died. Plants which were flooded for 12 hours during flood tide, dried up. The crabs and shrimps did not survive the transfer from a salty to a silt environment. The death of some sorts however meant the upcoming of others. Similarly, flounders and smelts were replaced by carps, perches and rock-basses. Nevertheless, the present balance was thoroughly disturbed in the years after the closure.