The fenlands in Cambridgeshire and Huntingdonshire were described as a watery wilderness in the eighth century, but by the twelfth century the richness of the area's resources as well as the reputation of its monastic houses led to a more confident view in ecclesiastical circles. The fenlands benefited from the onset of increasingly favourable ecological conditions as sea levels fell after c. 800, and by c. 1100 at least eleven monastic communities stood on islands in the fens and on the fen-edge. These monastic houses had by then become the most important landholders in the region and had established economic and social ties with each other and with secular communities. The monks of Ramsey and Peterborough exchanged eels for Barnack limestone, and monastic landlords leased out everything from hundreds (i.e. local government jurisdictions) to fishing boats on fenland meres to secular lords and local farmers respectively. Across the area secular and ecclesiastical communities shared access to fenlands under the authority of monastic landlords, who kept open the Roman waterways and dug new channels. Patterns of landownership and economic management established by the close of the eleventh century remained largely in place until the drainage of the fenlands in the late seventeenth century, and only in the late eighteenth century was an alternative means of managing the area within a collective framework successfully established on a permanent basis.