One would normally expect that an agrarian economy based upon both agriculture and husbandry would lead to an efficient, integrated system of land use. Ranching and herding would use land unsuitable for agriculture, and agriculture would convert its wastes into straw and silage for winter fodder. 47 Although our examples are limited, it would appear that this did not happen along the frontier. The pastoral industry of the Fenlands arose only when the agricultural production of the area began to decline as a result of the domination of military markets by the northern frontier districts. Fenland stock raising expanded over lands previously employed for cereal production. A similar process took place in Pannonia and Illyria, and probably in Moesia. The numerous small farms and villas of the interior of the frontier regions began to be absorbed by great estates when the districts immediately along the frontier became able to supply the local military demand for grain. Some of these great villas of the interior turned to ranching and herding for the military market. Thus again, pastoralism spread over abandoned agricultural lands or perhaps even displaced cultivation. Along the lower Rhine, both the Frisians and the Ampsivarii were desperate to be allowed to cultivate some of the lands set aside for military grazing. 48 Here, too, arable land was being used to support stock animals.
It is difficult to imagine why ranching and agriculture did not develop a complementary pattern of land use along the Roman frontier, but the present state of the evidence indicates that they did not. Such a failure could not have benefited either the economy or the society of the frontier regions. Agrarian development in the third century generally saw the disappearance of small farms and independent farmers, and the growth of great villas and conversion of plowlands into range. The great disparities of wealth and status characteristic of the heartland of the empire began to appear among the frontier societies. Thus, the rise of frontier ranching may have played a significant role in the decline of the cultural interchanges and social integration that had previously characterized these regions.