The Niederried artifical lake dates back to the construction of a river dam in 1913. The Site includes the lake on the River Aare, and natural stretches of the Aare and the River Sarine. The right shore of the lake features sandstone cliffs, while the left shore is dominated by flat water zones, alluvial forests and periodically flooded alluvial fens. Although the lake is of anthropogenic origin, the Site has evolved into one of the richest alluvial landscapes of the Swiss Plateau. The vegetation includes reedbeds, tall sedge marshland, meadowsweet fen meadows, small sedge reed, alluvial forest of silver willow, grey alder and ash, and beech forest. A particularity of the Site is the remarkable thermophilous flora on the sandbanks and sandstone cliffs. The Site is home to eight plant and 77 animal species figuring on the Swiss red lists of endangered species. It is an important wintering and stop-over site for waterbirds and other migratory bird species; however, silting up of the artificial lake and substantial changes in nutrient loads seem to be driving changes in the waterbird community. The other main factors affecting the Site are the artificial regulation of water levels and the warming of the water due to the nuclear power station in Mühleberg. Human activities such as recreation, agriculture and hydroelectricity production also impact the Site.