Geography and Demongraphics
Between the year 1000 and 1300 A.D., the population of Europe grew from 38 to 74 million. The growth of population was caused by a fertility rate that far outstripped the mortality rate. The population increase was also due to the lessening of warfare and a sense of added security.
To make this population increase possible, a parallel increase in agricultural production was necessary. This occurred because of two factors: a slight climate change that brought somewhat warmer weather to Northern Europe creating a longer growing season; and an improvement in the technology of agriculture, meaning the widespread use of iron implements, particularly the iron plow.