ploughing, by a shift in some areas to a three-field rather than two-field system of ploughing, so that land was less often fallow (though in the long run also less fertile), and by a general improvement in climate from the 1160s. Even so the margin of survival remained thin and a succession of severe winters in northern Europe at the end of the twelfth century brought widespread famine.

These developments were accompanied by a sharp rise in population. In some regions this could be contained within the available food resources, in others considerable emigration could reduce the pressure, but in some there came a point when the demand for food began to rise above what was available. When this happened the result might be a sharp inflation which could have profound political effects. Despite the increasing acreage brought under cultivation by land reclamation, and despite the development of alternative means of making a living in the woollen industry, Flanders was clearly suffering from overpopulation by the early twelfth century. As early as c. 1113, Archbishop Frederick of Bremen looked there for settlers to farm the eastern lands of his see, and other Saxon prelates and nobles followed his lead throughout the twelfth century. They did so to such effect that the population of Saxony is thought to have risen tenfold in the period 1000 to 1300, as opposed to a threefold increase for Germany as a whole. Such measures helped to relieve the pressure in Flanders but could not entirely curb its less welcome effects. The resultant inflation undermined the position of the Flemish nobility and brought what had been one of the best consolidated principalities into political uncertainty by the later twelfth century. Such developments operated with varying intensity and at different times in different parts of Europe and the respective strengths and weaknesses which they brought in their train could very greatly affect the relative strength of kingdoms and principalities.

With the growth of population came the growth of towns. They were supported largely by manufactures for the local market such as utensils or cloths but income also came from offerings at their shrines and the expenditure of their lords,

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