Feeding the Ten Billion Part 2

FEEDING THE TEN BILLION

PLANTS AND POPULATION GROWTH

L.T. EVANS

CAMBRIDGE UNIVERSITY PRESS                  1998

PART 1I

Chapter 3: Towards fifty Million (8000 BC – 2000 BC)

3.1 Introduction: From foraging to farming

Adam Smith thought mankind passed through an age of hunters and then an age of shepherds before the ages of agriculture and of commerce. However, this no longer seems likely, at least in the Near East where the domestication of crops accompanied that of animals. Nevertheless our hunting and gathering ancestors probably became farmers through a series of steps which should be described if we are able to be clear about what we mean by agriculture.

3.2 Shifting cultivation

3.3 The Neolithic Revolution

• In the Near East about 10,000 years ago several shifts in lifestyle and dependence took place more or less simultaneously which eventually had such  profound consequences for human civilization that the Australian archeologist V. Gordon Childe called them ‘the Neolithic Revolution’.
• The transition to domesticated crops and animals may have been simply as a supplement to hunting and gathering, and a not particularly welcome one at that given the additional labour involved in cultivation, the need to stay close to the stored grain, and the effort required to prepare these foods.
• One striking feature of the Near East is the close coincidence between the present-day distribution of the wild progenitors of wheat and barley and the location of the early farming villages across the ‘Fertile Crescent’.
• The Near East offers a particularly attractive and coherent model of domestication, plant, animal and human.
• There is a clearly defined center, or rather a crescent, with many well-preserved early Neolithic village sites scattered across Anatolia, Palestine and the Mesopotamian-Zagros mountain region.

 

3.4 Wheat, a complex crop

• The Yangzi Valley had its rice and central America its maize, but four of the world’s most important cereals – wheat, barley, rye and oats – all came from the Near East.
• There are many species of wheat besides the bread wheat which is now predominant.

Although the evolution of wheat as a crop occurred long ago, the manipulation of its genome still creates opportunities for further improvement, as may a retracing of some of the key steps in its evolution, eg by the synthesis of new hexaploid combinations. The future of wheat may be quite as complex as its past.

3.5 The agricultures of China

• Although rapid population growth did not always follow the adoption of agriculture, it did not occur without it, as Asian demographic history makes plain. The population of Asia grew 80-fold between 10,000 years ago and 400 BC, mainly in those areas adopting agriculture, such as China and India. Virtually no increase occurred in those areas such as Siberia, Korea and Japan where hunting and gathering remained the lifestyle.
• Northern India derived its agriculture initially from the Near East and for many years China was thought to have done likewise.
• China’s enviable collection of early texts and records such as oracle bones relating to agriculture offers many insights into early rural life and practices.
• China is, as Francesca Bray puts it, ‘the agrarian state par excellence’. It may well prove to have had the oldest of all agricultures, as Vavilov surmised. It encompassed the origin of several quite different agricultures, it played a crucial role in many later agricultural innovations, it has an exemplary written record of its agriculture, and it has given the world a great variety of food crops.

 

3.6 Rice, an adaptable crop

3.7 The Americas

3.8 Maize, the improbable domesticate

3.9 Africa: centers or non-centre?

Chapter 4: The First Half-Billion (2000 BC – 1500 AD)

• By 4,000 years ago, the adoption of the agricultural way of life was widespread and the population of the world was approaching 50 million.
• By the time of Christ, the world population is estimated to have been about 250 million, 27% in China and about 18% in each of India, south-west Asia and Europe.
• The drastic falls in the population of several regions which occurred periodically during the three and a half millennia suggest that agriculture was often unable to provide an assured and sustainable supply of food in the face of droughts, epidemics, wars and suppressions.
• The remarkable early records of yields on the Sumerian clay discs make it clear that the productivity of the downstream irrigation areas on the Tigris and Euphrates rivers declined disastrously due to silting and salting.
• Likewise, many of the hillsides of the Mediterranean lost much of their soil from erosion during this period.
• Although some high early yields of cereals were recorded both by the Sumerians and from the Nile Valley, most of the increase in food production for the ten-fold increase in population probably came from extension of the area of arable land, which was assisted by the introduction of the scratch plough or ard more than 4,000 years ago.
• Agriculture soon spread to the hills, aided by the introduction of terracing.
• The introduction of the heavy plough, and subsequently of the horse and collar, allowed the fertile bottom lands of northern valleys to be cropped, extending the arable area still further.
• Swamps and wetlands were drained or converted to water meadows or chimpanas, the latter often supporting large city states as in the Valley of Mexico and the Peten of the Maya.
• The agricultural wave advanced north-westwards across Europe at about one kilometer per year, and eastwards to the Indus Valley at about the same speed.
• As agriculture spread it also evolved. Oats and rye, minor components in the Fertile Crescent, became important crops at higher latitudes.
• With a widening portfolio of crops introduced into new environments came new needs and opportunities.
• The Roman two-course rotation could be changed to a three-course rotation at higher latitudes.
• This brought several advantages, such as greater and more stable food and then feed production, but also involved considerable social reorganization.

We also witness the profound effects of climatic change on the viability of agriculture. Just as such change set the stage for the Neolithic Revolution in the Near East, so also did it contribute to the decline of the agricultural base of several civilizations. The change to a warmer, drier climate over 4,000 years ago probably reduced the flow and increased the salinity of the Tigris and Euphrates rivers, spelling doom for Mesopotamia. Further east, the decline of the Harappan civilization coincided with the decline in the intensity of the south-west monsoon. The changing fortunes of the Nile and of the Aegean hills also reflect changes in climate, while the collapse of the Mayan civilization coincided with by far the driest episode in the climatic history of the region. Thus, while mismanagement of agriculture no doubt contributed to these declines, so too did climatic change.

4.2 The diffusion of agriculture into Europe

New techniques and concepts move around the world so rapidly these days that it is hard to grasp how slowly the agricultural way of life spread from the Middle East through Europe. It was not just that our communication systems are so much better now, because other early inventions, such as the plough or how to work bronze and iron, spread much faster than agriculture did.

• The spread of agriculture from Anatolia through Europe was primarily along the Mediterranean coast to Spain or up the Danube basin into Central Europe.

 

4.3 Passage to India

In 1926 when Nicolai Vavilov focused attention on just eight ‘centers of origin’ for the crop plants of the world, he made the Indian sub-continent one of the eight and concluded that ‘Índia is undoubtedly the birthplace of rice.’ As we have already seen, however, the oldest known remains of domesticated rice come from the Yangzi Valley in China.

• The earliest signs of agriculture in the Indian subcontinent come from the Indus Valley in the north-west.

 

4.4 Pastoral nomadism and the horse

4.5 The plough

4.6 Sumerian grain yields

• Having invented non-pictorial writing over 5,000 years ago, the Sumerians became compulsive record keepers and many accounts of cereal harvests, field by field, have survived on clay discs.

They tell an interesting story about siltation and salination. Agricultural settlement between the Tigris and Euphrates rivers – ie in Mesopotamia, ‘the land between the rivers’- began about 6,000 years ago. By 4,400 years ago there were well-developed principalities such as Girsu and Uma with smaller settlements aligned along the water courses and using some form of irrigation for their crops. Girsu at that time seems to have produced more or less equal amounts of wheat and barley, judging by the frequency of impressions of their grains on pottery sherds. The average yields recorded about 4,400 years ago of 2537 litres per hectare would be equivalent to about 2 tonnes per hectare of wheat, or 1.5 of barley. Such an average wheat yield per hectare was several times greater than Roman yields, and was reached in England only around 1900 AD, so it was remarkable.

It was not to last, however. Average yields in the Girsu area had fallen to 0.8 tonnes per hectare by 4,100 years ago, ie they were halved in a period of 300 years. And by 3,700 years ago they had fallen to half a tonne per hectare, by which time many of the Sumerian cities had declined to villages or ruins, while Babylon rose and political leadership passed to cities further up the river from the accumulating silt and salt.

• No doubt many elements contributed to the decline in the yield of cereals. Jacobsen and Adams have suggested that progressive salination of the fields occurred, beginning soon after the building of a large canal to bring water for irrigation from the Tigris about 4,400 years ago.
• Temple records attest to the appearance of salty patches in fields previously regarded as salt-free.
• Jacobsen and Adams cite progressive replacement of wheat by the more salt-tolerant barley. From being about half the markings made 4,400 years ago, wheat had fallen to 2% by 4,100 years and to virtually nil by 3,700 years ago.
• Although salting of the soil, possibly through more prevalent over-watering once the Tigris canal was built, undoubtedly contributed to the fall in cereal yields, many other factors may also have done so: a change in climate, loss of fertility after prolonged cropping, the silting up of canals leading to less reliable irrigation, or a decline in the power of the central government.

 

4.7 Terracing the hills