An abandoned clay workings on the southern banks of the Humber is to become a designated nature reserve.
On Friday, Far Ings, near Barton, will be declared a National Nature Reserve in recognition of the area's importance for wildlife.
Lincolnshire Wildlife Trust took over the management of the complex of lakes, reed beds and meadow in the 1980s.
The old clay pits are now home to the bittern, marsh harriers, bearded tits and kingfishers.