The structure of relief profoundly affected communications. For instance, the line of the Via Flaminia, after leaving the volcanic landscape of South Etruria, followed the natural tectonic valleys of Umbria, seeking out a pass in the Apennines to find an exit to the Adriatic Sea. The larger rivers could also have been effectively employed, particularly downstream, to carry mountain resources of wood and stone into the alluvial zones relatively poor in such resources and generally the location of the major cities.
The modern rainfall of the Italian peninsula is profoundly determined by relief and season and there is every reason to think that this would have been broadly the same in the republican period. Annual rainfall exceeds 1,000 mm above 1,000 m and drops to lower levels in the hill and coastal regions, ranging from 800-900 mm in the Arno valley to 600-700 mm in Apulia. Certain zones such as the Tavoliere have particularly low rainfall.
The drainage of the peninsula is also determined by the nature of the structural relief. When coupled with seasonal patterns of rainfall and the porosity of some of the parent rocks, there is a profound seasonality to the flow of many of the rivers. The western side of the Apennines is dominated by five long rivers with large catchments, draining into the Tyrrhenian Sea. These are followed in rank by seven shorter rivers with smaller catchments on the eastern side of the Apennines draining into the Adriatic or the Gulf of Taranto. This effect is particularly marked in central Italy where the two largest rivers, the Arno and the Tiber, dominate their landscapes with sizeable catchments. The longest river is the Tiber, which rises on Monte Fumaiolo in the northern part of the central Apennines and runs some 405 km, draining a catchment of some 17,169 sq km. Its course is first directed south in a route determined by tectonic valleys, and then southeast in its lower reaches, redirected by Pleistocene volcanic action, toward its delta near Ostia. In the course of this flow it changed from a more seasonal river in its upper reaches to the perennial and substantial flow once joined by tributaries such as the Aniene and Nera. This river was an important line of communication since it was navigable up into the higher reaches, although more reliably from Orte south, as supported by the archaeological presence of port installations at Ocriculum, Horta, and Lucus Feroniae.35 The Arno rises in the Apennines at Monte Falterona (1,654 m) and runs some 241 km in a route also determined by the tectonic basins, covering a catchment of some 8,247 sq km, until it reaches the sea at the modern Marina di Pisa. The next three largest rivers all drain the western flank of the Apennines and are placed in central (Ombrone - 161 km, 3,480 sq km) or southern central Italy (Volturno - 175 km, 5,455 sq km; Liri-Garigliano - 158 km, 5,020 sq km). The next seven largest rivers drain the eastern flank of the Apennines, ranging in size between 149 and 101 km in length and 3,188 and 1,192 sq km in catchment.
These differences in scale provide an important constraint on the scale of political process. Smaller-scale river systems (such as in Calabria) provide a limit to the scale of urban development. The Greek colonies in this region tended to have small hinterlands. Larger-scale river systems (such as the Tiber and the Arno) offered greater potential for the development of an agricultural and industrial infrastructure, as well as larger territorial limits. These river systems permitted the development of the great civilizations of the Etruscans and Latins. Intermediate to these scales are intermontane basins of Gubbio and the upper reaches of the Biferno around Bovianum, which formed natural territories for small urban systems.
Altitude also had an effect on health. Many of the coastal areas below 500 m when combined with specific lagoonal conditions with stagnant water of the right salinity could have provided the right conditions for malaria. Erosion from the uplands, perhaps a consequence of more intensive land-use in the republican period, would have provided extra sediment that contributed to the ponding of lagoonal water along the coast. These changed conditions may have favored an extension of mosquito-breeding conditions. If these conditions existed in specific locations (most particularly in summer and autumn), altitude would have been a way of escaping the lazy mosquito, which is reluctant to engage in long altitudinal flights. However, extreme altitude would have provided its own risks of cold, ruggedness, and low productivity.
Altitude also affected economic potential. Studies of traditional land use, although not directly transferable to the Roman past, point out the major differences which can be tied into literary and archaeological evidence.3 Mediterranean types of cultivation (olives, vines, fruits, wheat, and maize) were restricted to the lower hillslopes, valleys, and basins. The traditional method of cultivation was coltura promiscua, that is, the polyculture or growing together of olives, vines, and cereals to provide temperature and water control. The rearing of animals (chiefly sheep, but also cattle and pigs on the central Apennines and goats in the south) was concentrated on the less fertile ground. An important issue is that of transhumance, an agricultural practice which exploits the contrasts between upland and lowland to move flocks between lowland winter and upland summer pastures. A number of scholars have emphasized the longstanding presence of these economic practices as one potential strategy, facilitated by the mountain-plain structure of the Italian peninsula, requiring political networks as well as ecological complementarity for their effective execution.37 Modern practices suggest that there were two alternative strategies for sheep and goat rearing. One was transhumance, involving in the most elaborate instances large numbers of animals driven over large distances. The other was to hold the smaller numbers of animals in stalls at night (providing manure for arable cultivation) and then allow them to graze locally. The implications of these issues are discussed in Chapter 27.
World History
