Lake Vänern has northern Europe´s largest freshwater archipelago with 22 000 islands, islets and skerries. The lake has plenty of nesting birds and is also an important resting site for migrating birds in the spring and autumn.
The lake host many fish species; there are 38 permanent species in Vänern and both cold and warm-water species mix. The most common fish in the lake is smelt.
The catchment area is dominated by forest, about two-thirds of the surface. Arable and pasture is covering one-sixth, most of this located in the southern part of the lake.