Did bocage farms enclosed in hedgerows provide protection as field fortifications fro mounted raiders? Did it reduce soil losses or enhance soil fertility? Reduce run-off and provide better water conservation?
Did the type of farming change? In England from the 14th c. there was an increase in wealthier land owners enclosing land because they were switching from arable farming to livestock farming. With arable it was useful to have large tracks of land because it was more convenient for ploughing, but with livestock it was more convenient to enclose smaller patches of land to keep livestock in and thieves and predators out.
http://www.thelandmagazine.org.uk/articles/short-history-enclosure-britain