If the imperial bishops opposed the new movement, it was mainly owing to the influence of the monks, and especially the Cistercian monks, that it spread to agricultural districts and that the rise of the communes coincided with the abolition of serfdom. The direct consequence of the development of trade and industry was the depreciation of the land, and it became necessary to open new districts to agriculture. The Cistercians were pioneers in this direction. They established their houses in barren heaths and marshy districts, and applied their skill and patience to converting them into fertile fields. Unable to carry on the work unaided, they appealed to lay brethren, who established farms in the neighbourhood of the monasteries. These peasants were no longer serfs but free peasants, as had been their forefathers after the Frankish invasion. Under the supervision of the monks and of the stewards of dukes and counts, who soon realized the advantages of the Cistercian method, they created new "polders" along the Flemish coast, cleared the forests of Hainault and Namur, and reclaimed the heaths and marshes of Flanders and Brabant. The reclaimed ground was divided among the workers, so that, at the beginning of the thirteenth century, a new class of free peasants replaced the old class of feudal serfs. The farm produce was no longer for local consumption alone; it was taken to the market-place, where the farmers met the merchants and artisans. The social transformation begun in the town halls spread thence to the country-side, and the whole country began to share the same economic and political interests.