In reply to wbo:
Well, if we were to stop the process of agricultural grazing and the intensive micro-management of heather, we would over time see more and more tree/saplings and dwarf shrubs appear, which in turn would give way to the re-establishment of native woodland across the moors. A canopy would then lead to a decline in heather and bracken coverage and the very slow development of a 'traditional' forest floor.
This would however take a very long time but is the basic idea behind the natural direction the landscape would take. To put it simply, there'd be a bit more diversity!