At the time of the Slavic settlement, the flat periphery of the Alpine world was partly inhabited, and in the late tenth and eleventh centuries incorporated into the feudal social and economic system, with the territory being divided among several landlords. In the eleventh century, intensive colonisation at the lower altitudes began, culminating in the twelfth century and completed by the thirteenth century. At the same time, the settlement of the upland area started, which in some areas extended into the fifteenth century. Particularly in the Alpine valleys, animal husbandry and cheese-making were a principal source of livelihood. Arable farming was second to stock-raising; however, grain was cultivated throughout the region. Alpine streams and lakes were exploited for fishing. Deforestation intensified over time, initially to acquire more agrarian land, and from the fourteenth century onwards to meet the needs of charcoal production, which was the traditional fuel for the growing number of ironworks. Both the development of the iron industry and several transport routes via the Slovene Alps were central to the social and economic development of the region in the Late Middle Ages.