The extraction of peat from the marshes of the lower river was known in the 16th century; peat being the principal means of heating and also a multi-purpose fertilizer. The alder tree, which grew well in the local marshy soils, contributed to bind the ground, and produced timber. It was realized that forestry also helped in drainage. Further developments in the 18th century saw permanent enclosures with animals being fenced-in, keeping them off the crops, and property boundaries being created by the planting of hedges and the digging of ditches, contributing to organized and cooperative farming methods.