FEEDING THE TEN BILLION
PLANTS AND POPULATION GROWTH
L.T. EVANS
CAMBRIDGE UNIVERSITY PRESS 1998
PART 1II
4.7 Terracing the hills
- Although agriculture may have begun in the lowlands, population and other pressures soon led it into the hills, where the spread of farming was soon associated with the development of terrace agriculture.
- In the Mediterranean regions where heavy autumn rains followed a long dry season on soils of limited storage capacity, the clearing of the hillsides for cultivation often led to heavy run-off, soil erosion and an accelerating cycle of water, soil and nutrient loss from the hills coupled with excessive accumulation in the valleys as marshy, malarial swamps.
- Much of the damage was done in the Hellenic period, beginning about 2,800 years ago. Like the cedars of Lebanon before them, the forests were cleared for timber, the land was ploughed and the cycle of erosion began.
- Even 2,800 years ago, Homer referred in the Iliad to the tilled fields of men being wasted by the torrents rushing headlong from the mountains.
- Solon later recommended the cessation of cereal cultivation on the Attic hillsides.
Plato summed up the situation in one of his Dialogues: ‘What now remains of the formerly rich land is like the skeleton of a sick man. Formerly, many of the mountains were arable. The plains that were full of rich soil are now marshes. Hills that were once covered with forests and produced abundant pasture now produce only food for bees. Once the land was enriched by yearly rains, which were not lost, as they are now, by flowing from the bare land into the sea. The soil was deep, it absorbed and kept the water in the loamy soil, and the water that soaked into the hills fed springs and running streams everywhere. Now the abandoned shrines at spots where formerly there were springs attest that our description of the land is true.’
- So here was an articulate civilization in the throes of expansion, well aware of what it was doing to its own countryside yet seemingly unable to moderate the demands of its growth in population and power.
- Likewise, a little later, in the Apennines of Italy. Thus, ‘the glory that was Greece and the grandeur that was Rome’ were built on, and eventually undermined by, the denudation of their hills and mountains.
- In areas of seasonal rainfall, terraces helped to conserve both soil and water. They could also concentrate run-off for the irrigation of perennial crops, as in the Negev.
- The earliest known terraces in China date back to 2,200 years ago, but they were not common before the 9th century AD.
The large-scale terracing of Andean and Asian hillsides required the sustained cooperation among those working and maintaining the terraces at various levels, over many generations. Neglect could quickly lead to the failure of some terrace walls leading in turn to the breaching of others lower down. The hills of Asia and South America are living testimony to the value of terrace-building in the creation of agricultural landscapes that are both attractive and of sustained productivity. Equally, the many abandoned and eroded remains of terraces throughout the Mediterranean, as well as the ‘divine nudity’ of the hills, bear witness to the destructive power of unwise cultivation.
4.8 Chinampas and the collapse of the Maya
4.9 The fabled Nile
4.10 The maintenance of soil fertility
Compared with the philosophical bent of the Greek writers on agriculture, the Roman authors from Cato to Columella grounded their writings more firmly in their practical farming experience. Their lives coincided with the decline of the independent peasantry during the late Republic, and their experience derived from the large, slave-operated estates, the latifundia.
The earliest of them, Cato the Censor (234-149 BC), was a champion of the common people and the simple life. His De Agri Cultura is a rather rambling account of traditional practices. Varro (116-27 BC) began his Res Rusticae in his 80th year. Virgil (70-19 BC) derived much of his agricultural knowledge from Varro’s three books, but it was his Georgics which carried Roman practices to the outlying parts of the Roman empire and through the Middle Ages.
Finally there was Columella (4 BC – AD 65), whose Res Rustica in 12 books was the most comprehensive and systematic of the great Roman treatises on agriculture. Columella begins his work by denying the apparently widespread view that soils, like people, necessarily become worn out with age and over-production, in the extreme becoming ari deserti, ie deserts. Rather, he says, their loss of fertility is due to the formerly careful husbandry of the Roman farmers being handed over to the latifundia slaves ‘as if to a hangman for punishment; whereas for oratory, mathematics, music, shipbuilding or war one goes to experts for training, the most important art of all, agriculture, is as destitute of learners as of teachers.’
Columella’s treatise therefore offers detailed practical advice on all aspects of agriculture: how to yoke and handle your oxen in ploughing, always across the slope by the way; when, where and how to sow the many crops and their varieties; the uses of various implements and types of drainage; the number of labourers required, etc. A dominant theme throughout is the maintenance of soil fertility, ‘quickening the earth’, by the use of animal manures, green manures and crop rotations.
The traditional practice on lighter soils throughout the Mediterranean region was to allow the land to lie fallow for a year between autumn-sown wheat crops, partly to conserve moisture and partly to restore soil fertility. Cato was aware of the beneficial effects of crops of lupins, broad beans and vetch on soil fertility. Varro comments that besides forage crops such as clovers, vetches and lucern, the legumes (so-called because their grains were gathered (leguntur), also enrich the soil and should ‘be planted not so much for the immediate return as with a view to the year later’. He goes on to say that it was customary to plough under broad beans and lupins before the pods were formed, as green manures in place of dung, if the soil was light.
By the following century Columella had added peas, chickpeas, lentils and other legumes to the list, and the practice of rotational green manuring for fertility maintenance seems well established. Columella and Pliny both list several schemes of crop rotation involving not only cereals and legumes, but other crops such as turnips for winter feed.
- At about the same time as Varro and Columella were writing in Italy, the Chinese were recording several parallel advances in agriculture.
- Continuous cropping with a variety of rotations was well established in many parts of China by the first century BC, thanks to the eclectic array of manures used by Chinese farmers, not only green but also animal, human, composts, ashes, bones, silkworm droppings, hair, etc.
For the next 1500 years in Europe, soil fertility and the supply of animal manures severely limited cereal yields with the result that increases in population had to be matched by expansion of the area of arable land. However, the marling and crop rotations devised by the Romans and Chinese at least helped to prevent long-term declines in cereal yields, if not their disastrous variation from year to year.
4.11 European agriculture in the Middle Ages
- The Middle Ages were by no means a millennium of standing still in European agriculture.
- For most of Europe, yields of cereals at the beginning of the 14th century were not surpassed until the 18th or, in parts of France, the 19th century.
Northern Europe in the 5th century AD was covered by forests in which oxen were grazed, while cleared patches under temporary cultivation grew mostly wheat, barley and rye in the Roman two-course rotation of one year in autumn-sown crop followed by one in fallow. As the Millennium progressed and the landscape became more settled, the crops became a major cereal, and spelt wheat, buckwheat and several legumes became more significant in diets with migration northwards.
- Associated with the change in crops was the shift from the two-course to a three-course rotation, with the first year in autumn-sown winter wheat or rye, the second in spring-sown oats, barley, peas, beans, lentils or chickpeas, and the third under fallow.
- It has been called ‘the great agricultural novelty of the Middle Ages in Western Europe.’
- The advantage of the three-course rotation included: increased crop production; less risk of famine; more evenly spaced use of labour and draught power; better diet and improved soil fertility from the legumes and more abundant oats as feed for horses.
- The plough also evolved during the Millennium.
- The fourth major change was the shift to horse power, made possible by the more frequent cropping with oats in the three-course rotation.
Widespread ploughing with horses in the 11th century led to a need to consolidate and rearrange peasant holdings. Moreover, the peasant no longer had to live so close to his land, so there was a shift in the population from small hamlets to larger villages, with more educational and commercial opportunities, and more cooperation between peasants. Especially in England, where the manorial system did not develop until the 11th century, the landlord-tenant nexus became more flexible.
- Taken as a whole yields remained low and unchanged throughout the Middle Ages.
- Average wheat yields in England were still only 0.8 tonnes per hectare in 1450 AD.
- Famines were frequent, that of 1314-16 being widespread through western Europe.
- What with the plague as well, the 14th century was not a good time to be alive.
- It was not until the end of the 15th century that further innovations made higher yields possible.
Chapter 5: Towards the First Billion (1500-1825)