Following the last glaciation Lake Pickering gradually drained away leaving a complex of rivers and marshes. The carrs, marshes, ings and wet meadows have now all been drained by humans and, as well as the rivers, the landscape is crossed by a network of canalised drainage ditches and canals which regulate the water table. In spite of this legacy of river engineering and land drainage the rivers of the Vale of Pickering remain one of the most important wildlife features of the area. There are many species of aquatic birds, plants insects and mammals inhabiting the riparian areas and greyling and brown trout fish thrive in the rivers of the western area.