Not a good specific source, but Court's Concise Economic History of Britain might help. I am sure a specialist has a better source on this particular topic, though.

Enclosure benefits those who can take advantage of it -- instead of an open field system which allowed a lot of peasants to make small economic advantage off of the fields, enclosures restricted use to a few aristocrats who got a great deal more money off of pasturage, generally by raising sheep for wool. A given lot of X number of acres could make more money as pasturage than arable land. On the other hand (and indeed, as a great part of the cost savings) pasturage took a great deal less labour, and thus peasants who had once worked the land were displaced since only a few of them were needed to care for animals. Thus, it was the aristocracy that could afford to enclose and raise animals that benefited.

The process took place over a long time, going back to an early boost in the Tudor area. I have seen a natural drop in population during the period cited as the impetus for the process, although the economic gains led to its continuing.