Rome: An Empire's Story (11 page)

The reasons are fundamental. Plant and animal species move most easily within the same latitudes, where mean temperatures are broadly similar. Migrations of species—both the re-colonization of Europe after the glaciers retreated, and the spread of the cultigens and domesticated animal species created by the first farmers—took place most easily between similar environments. The expansion of the Sahara accentuated this effect, creating a barrier between the Mediterranean and the rest of Africa. Ecologically, the Mediterranean world is a long corridor leading westwards out of western Asia. The climate becomes significantly wetter further west owing to the proximity of the Atlantic. Within the Mediterranean this is expressed in the differences in rainfall between the wetter west-facing coasts of Italy, Greece, and Turkey, and their more arid east-facing coasts. The further west along the corridor a species moved, the greater the contrast with the ecology within which it had originated. It is as if the corridor was at a gradient, sloping upwards, so making westward progress increasingly difficult.

Domesticated animals first appeared in Europe in the third millennium
BC
and again spread westwards. The origins of domestication were again mostly in the Near East, and the main domesticates were widespread by the start of the last millennium
BC
. Oxen and horses provided traction. Cattle, sheep, goats, and pigs provided meat. Cattle, sheep, and goats might be milked. Sheep and goats provided wool. All might provide bone and leather, and in sophisticated agricultural regimes manure as well. By the end of the second millennium
BC
, humans were using one or another variation of this complex of cultigens and domesticates across Europe and the Mediterranean. Geese had been domesticated in ancient Egypt. Chickens, descended from jungle fowl in the Far East, appeared sometime in the middle of the last millennium. (There are no chickens in the
Iliad
, but Socrates’ last words were that he owed a cockerel to the god Asclepius.) Camels, domesticated much earlier in the Arabian peninsula, also moved progressively further west during the last millennium
BC
. Rabbits were
confined to the Iberian peninsula until the turn of the millennium. Small animals might seem insignificant, but they were valuable as they might be bred fast and fed cheaply. In a world without refrigerators, small animals also posed fewer meat storage problems.

The main technological innovations in agriculture also preceded Rome. Most important was metallurgy, also invented in the east. Gold was easiest to extract, but was nearly useless for making tools. Copper and then bronze working began in the Near East in the middle of the fourth millennium
BC
. What really made the difference to agriculture was the appearance of abundant iron tools, cheaper to produce and harder wearing than other metals. Ironworking was almost certainly discovered in north-west Anatolia towards the end of the second millennium
BC
: from there it spread throughout the Old World, reaching the Yangtzee, southern India, and Scandinavia by the middle of the last millennium
BC
. Iron agricultural tools were especially important in northern Europe where they made forest clearance and the cultivation of heavy soils much easier. The growth in the availability of iron tools in the middle of the last millennium
BC
runs parallel with agricultural and demographic expansion in the European interior. Evidence is provided not only by the great size of late Iron Age hillforts and other settlements, but also by the huge armies that began raiding and invading the Mediterranean world from the fourth century
BC
. Greeks and Roman were terrified by these invasions, but had no real notion of their causes.

The temperate Europe that Julius Caesar and his successors found when they began serious warfare north of the Alps was already tamed. There were no longer any hunter-gatherer populations. Not was there any primeval forest. Forests had expanded in the early Holocene, following the retreat of the glaciers, but they had mostly been felled by the first farmers. The woodlands that replaced them were created and managed by human activity. Roman poets wrote of northern Europe as utterly savage, a continent of dense forests full of wild beasts. But Roman generals, and the tax collectors that followed in the early empire, will have appreciated the phenomenal agricultural productivity of European landscapes compared to the arid Mediterranean. Forests and game certainly survived, as they do today, but only on the higher ground between cultivated landscapes. Around the Mediterranean there was already the present-day landscape of
garrigues
, a characteristic type of shrubland rather like
chapparal
formed of plants that can tolerate the summer heat, alternating with small cleared plains on which cereals might be grown.

Prehistoric agriculture was not limited to the production of grains: woodlands and wetlands were also exploited; salt, vital for preserving meat and fish, was mined, gathered from coastal salt pans, and traded; large herds of livestock were raised, and short-range transhumance was already practised. The range of animal and plant species cultivated by prehistoric societies might seem relatively small, but the impact of farming on the early Holocene fauna was already phenomenal. The top predators who had expanded out of ice age refugia into Europe now diminished in number as their prey and habitats were removed. Lions disappeared from Europe and eventually western Asia, while populations of wolves and bears were fragmented. Greek heroes fought with savage beasts that threatened grain-growing lowlands, monsters like the Nemean Lion and the Calydonian Boar. Those myths reveal a world already imagined in terms of a stark opposition between civilization and the wilderness. And the wilderness was in retreat. Over the Iron Age and Roman centuries, smaller domesticated cattle replaced aurochs in temperate Europe, and bison and elk were restricted to the far north. Deer retreated into the remnant forests and resurgent woodlands. Hunting became rarer and less exciting. When the Emperor Trajan wanted to hunt game in Italy, he had to climb to the summits of the Abruzzi. The Roman generals who conquered the east were amazed to find Hellenistic kings had, in imitation of the Persian emperors, created reserves in order to preserve animals worthy of a royal hunt. The Persian word was
paradeisos
, giving us our term ‘paradise’. Wilderness had become a scarce commodity, a luxury that needed to be conserved and cultivated. We can easily imagine this today, just as we can easily imagine the rich rewards that would follow Roman possession of the waking giant of temperate Europe.

Ecology and Empire

Imperial expansion since the fifteenth century has often had dire environmental consequences. One reason is that globalizing movements often connected up regions that had been out of contact for long periods. Most dramatic was the Columbian Exchange of plant and animal species that followed European discovery of the Americas, leading to extinctions and the catastrophic merging of disease pools, as well as the transformation of Old World diets with the introduction of coffee and chocolate, potatoes and cane sugar.
¹²
Then there have been deliberate modifications of colonial
ecosystems in modern times, such as the creation of cotton and coffee plantations in the Americas, the introduction of cattle ranching into parts of North and South America, of sheep farming into Australasia, and the transplantation of maize from the New World into Africa. Cash crops often replaced subsistence agriculture, and the needs of distant imperial markets took priority over those of indigenous populations who were sometimes dispossessed, and sometimes conscripted to labour within new agricultural regimes. Slavery notoriously allowed the wholesale movement of human populations. There are some prehistoric precedents. Human expansion at the end of the Pleistocene era, into first Australia and later the Americas, seems to have led to the extinction of native megafauna, from two-tonne giant wombats and three-metre-tall kangaroos to the American lion and giant sloths. The settlement of the Pacific Islands and New Zealand was accomplished only because explorers took pigs, chickens, dogs, and various domesticated crops with them in their canoes.

Roman expansion did not have such dramatic effects. The empire expanded within a region the inhabitants of which used broadly the same domesticated species as themselves. When areas beyond the Mediterranean were eventually incorporated into the empire, this was usually just the latest phase in long histories of contact. As a result, Romans rarely encountered economies or ecologies very different from their own. The environmental changes that Roman expansion brought were, on the whole, more piecemeal and more subtle than those introduced by European empires.

All this marks an important difference between the ecologies of modern and ancient empires. Roman expansion was facilitated by what the conquerors shared with their new subjects. The first tax levied (on Sicily) was a simple tithe of grain, and when armies campaigned in Spain in the second century or Gaul in the first century
BC
, their local allies were expected to provide food. African Lepcis paid a great indemnity in olive oil, and the Frisians at the Rhine mouth were taxed in hides. Taxation in kind was always an important part of Roman fiscal systems. Yet even when cash was required provincials could earn it simply by intensifying the production of crops they already grew, since these were the crops Romans already knew and desired. Monocultures and cash crops never squeezed out pre-existing regimes in the Roman period. We know of no disastrous experiments with new crops. The empire expanded into regions that were already productive, and in most areas did no more than stimulate a modest intensification.

The political unification of the Mediterranean has even been seen as simply the latest—political—phase in a much longer story, one that had begun with the spread of farming out from the Near East. It has been suggested that the limits of Roman expansion were set, in some regions at least, by the limits of this Old World agricultural complex. To be sure there was no ecological frontier dividing Roman from Persian spheres of influence, indeed that frontier cut through areas in north Syria that in every possible respect—cultural, religious, technological, and ecological—formed a unity. Yet Rome’s northern frontier at points reached areas where the returns from this style of agriculture do not seem to have been impressive during the Iron Age. Perhaps Roman conquest reached an ecological limit in northern Britain or the Low Countries.
¹³
Most of the long European frontier ran through rich agricultural land. Where Roman rule did meet real ecological limits was the Atlantic and the Sahara. The empire had successfully gained control of the southern part of that western corridor leading out of the Near East: threats came to it from north and east.

Roman expansion followed agricultural change, and brought with it few new technologies, species, or diseases: consequently, Roman conquest had no cataclysmic ecological impact. But this does not mean that Romans were not positively interested in promoting intensification. One sign of Roman interest is the care they took to learn from the agricultural regimes they incorporated. The only book the Romans took from the libraries of Carthage after the sack of the city in 146
BC
was Mago’s agricultural treatise which was then translated into Latin. Generals returning from the east brought back new species of plants, including cherry trees. Roman writers of the early empire were actually very well aware of how recently many nuts and fruit crops had been brought to Italy from the east. More than 40 per cent of the plants named in Columella’s first-century
AD
book
On Agriculture
were Greek in origin. The
Natural History
of his near contemporary Pliny the Elder describes in detail the various trees and other crops found in different parts of the empire, and their nutritional and sometimes medical benefits. Medical texts produce a wealth of information about cultivable species. Pliny was just as interested in the plants and animals of the western Mediterranean and even temperate Europe, but it is obvious from his account that the main direction of movement remained east to west.

Roman entrepreneurs not only brought eastern crops to Italy, but also attempted to transplant various Mediterranean species north of the Alps. Apples, pears, cherries, plums, and walnuts were introduced to northern
Europe very early on, as were celery, garlic, asparagus, cabbage, and carrots. Chestnut, probably used for wood rather than primarily as a food source, followed a little later. What these trees and vegetables had in common—and what separated them from cereals—is that they required cultivation in gardens or orchards. Arboriculture involved a range of new specialized skills, such as grafting. It also required much greater inputs of energy and time in return for greater calorific and financial returns per hectare. The northward progress of these crops—like that of the vine—reflects the spread of Mediterranean taste, as well as of agricultural knowledge. Carbonized remains of these crops appear on settlement sites alongside those of others that could not be domesticated north of the Alps including figs, chickpeas, pistachios, almonds, pine kernels, and melons. The expansion of arboriculture and gardening was also closely linked to urbanization. Not only is it labour intensive but it also relies on levels of consumer demand most easily found where populations are densely packed and relatively prosperous. It also offers vital supplements to a diet high in carbohydrates, providing sugar, protein, and vitamins. It was urban populations that had the greatest needs of these supplements.
¹⁴
It is no accident we know most about it from Roman Egypt and the environs of Rome, the most urbanized parts of the ancient world.

More generally, the spread of arboriculture allows us to observe Romans as enthusiastic adopters of new cultigens. Profit and the desire for a wider range of tastes were no doubt key motivators. But there was a sound ecological logic too. The principal weakness of the earliest agricultural regimes in all parts of the world was the small number of cultigens on which each depended. Dependence on a single crop is enormously risky, and diversification provided a key buffer against crop failure. Hence the early importance of pulses, and the steady growth of the variety of grains cultivated, naked wheats joining emmer and einkorn alongside spelt and barley, and rye, oats, and millet being grown in some regions. The wider range of cereals did not only provide better matches for particular local microclimates. Barley was less favoured as a food but could resist drought, millet could be grown over the summer, chestnuts and other nuts provided a key protein source when crops failed, or fodder for pigs when they did not. The range of cultigens increased over time.