Feeding the Ten Billion Part 8

FEEDING THE TEN BILLION

PLANTS AND POPULATION GROWTH

L.T. EVANS

CAMBRIDGE UNIVERSITY PRESS                  1998

PART VIII

Chapter 8: The Fourth Billion (1960-1975)

8.1 Introduction: focus on development

It took a century to add the second billion to the world’s population, and 33 years to add the third, but the fourth took only 15 years. The highest rate of growth of the world population, of 2.1% per year, was reached in the 1965-70 period. Not long after our numbers reached three billion and the technological triumph of sending satellites into orbit, we saw the first photographs of the earth from space, a small planet in need of care and maintenance if humankind was to survive. The growing concern for ‘only one earth’ became the focus of the first United Nations Conference on the Human Environment in Stockholm in 1972 as the world population approached four billion with what Barbara Ward and René Dubos referred to as ‘sober optimism’.

• The contrast between the rapid rise in population and the sluggish increase in food production in the less developed countries, where most of the fourth billion were added, 69% of them in Asia, demanded attention.

The mid-1960s droughts in India exacerbated concerns, as exemplified by the conclusion of the 1967 report of the US President’s Advisory Committee that ‘The scale, severity and duration of the world food problem are so great that a massive, long-range innovative effort unprecedented in human history will be required to master it.’

• The following year saw the establishment of the Club of Rome and the publication of The Limits to Growth.
• Another strand in the prevailing pessimism was the sharp decline in carryover stocks of grain in the world, from about 100 days’ supply in 1960 to only about 40 days in 1974 following the oil price crisis of 1972/3, which led to a temporary slump in grain production.
• In 1971 the Consultative Group on International Agricultural Research (CGIAR) was established to support a more comprehensive system of international agricultural research centres to work in partnership with the less developed countries.
• Its founding fathers had been greatly encouraged by the early successes of the dwarf wheat and rice varieties first released in 1962 and 1966 respectively.
• By 1970 the dwarf varieties occupied almost a quarter of the total wheat area in developing countries (excluding China), 40% by 1975 and today about 70%.
• The dwarf rice varieties had a similar course of uptake and impact. By 1980 they occupied about 40% of the area sown to rice in south and south-east Asia, and 74% by 1990.

As with the dwarf wheats their use was often associated with irrigation and greater use of fertilizers. Together these resulted in a steady annual increase in rice yield and production of about 3%, to which the new varieties, irrigation and fertilizers contributed about equally. Thus, as a result of the synergistic interactions between these three factors there was indeed a Green Revolution, and the supply of staple foods more than kept pace with the rising population. Indeed, from 1975 on the FAO index of food supply per head in developing countries began to rise, and the real prices of wheat and rice continued to fall.

• In India the dwarf cereals not only increased the supply of protein, but substantially reduced its price.
• During the 1970s many social scientists criticized the Green Revolution because it favoured the larger farmer; it reduced employment opportunities; it led to both national and individual dependence on agrichemical companies and creditors; it affected the health of both farmlands and rural environments adversely; it disadvantaged the grain legumes and weakened crop rotations; it made yields more variable and genetic resources more vulnerable.
• There had to be costs – social, environmental and agricultural – if the world food supply was to be increased rapidly. However, rural employment opportunities increased, small farmers eventually benefited as much as their larger neighbours, the ‘revolution’ spread far beyond the favourable irrigated areas and food supplies did not become more vulnerable.
• The ultra-poor and hungry remain so, unfortunately.
• By raising yields substantially the dwarf cereals took pressure off the expansion of arable area to such an extent that further land clearing for agriculture merely matched the losses to urbanization and soil degradation.
• Lending for agriculture and rural development by the World Bank rose from about 1% in 1959 to almost 40% of its loans 20 years later.
• Surpluses, surfeit and subsidies troubled the 30% of people living in the developed countries while the less developed 70% faced deficits, debts and deficiencies.

The developed countries began to register the social and environmental perils of excessive or careless applications of agrichemicals. In 1962 this growing concern was crystallized by Rachel Carson’s book Silent Spring, which focused on the environmental hazards of pesticides such as DDT, herbicides and other chemicals used in agriculture.

• Unwelcome side-effects of many agrichemicals were uncovered, including those of fertilizers such as eutrophication and nitrate contamination of groundwaters.
• Techniques for applying irrigation water greatly improved, as were the strategies for using resistance genes in plant breeding programmes to minimize the use of agrichemicals.
• There was an air of confidence as we approached our four billion, exemplified by the rash declaration of the 1974 World Food Conference ‘that within a decade no child will go to bed hungry, that no family will fear for its next day’s bread and that no human being’s future and capacities will be stunted by malnutrition’, despite the famines in the Sahel in 1972-74 and in Bangladesh in 1974.

 

8.2 The dwarfing of wheat and rice

The greatest impact on world food production as the population grew towards four billion came from the deployment of the dwarfing genes in wheat and rice in the 1960s. Like many other advantages we have considered, its origins were much earlier and its impact is still increasing, but it came to fruition just when the escalating use of nitrogen fertilizers made it necessary and the development of herbicides made it possible.

Until the 1960s, tallness in cereals was an advantage. The straw was valuable for roofing, mulching and for livestock feeding and bedding, yielding large amounts of farmyard manure, important as fertilizer and a valuable fuel in many developing countries. Height was also needed to allow the cereals to compete more effectively with weeds. With rice, particularly, taller plants were better adapted to traditional harvesting by hand.

In several east Asian countries in the latter half of the 19^th century, however, shorter varieties of both wheat and rice began to be used. Less dependence on weed-infested farmyard manures and more intensive hand weeding reduced the need for tallness, while their heavy use of fertilizers made shorter, stronger stems desirable to avoid the lodging of crops.

• After about 1900 the height of many European wheat varieties began to fall from one and a half metres to reach about one metre by 1960. However, this change was gradual and did not involve the use of dwarfing genes of major effect. For these we have to return to east Asia.

In Japan in 1917 the semi-dwarf wheat variety Daruma – which may have come from Korea – was crossed with an American variety and the progeny of that cross were then crossed with another American variety in 1925. Selection from the progeny resulted in a semi-dwarf variety called Norin 10 which was included among the dwarf Japanese varieties taken back to the USA by S.C. Salmon in 1946. There it was crossed by Orville Vogel with an American variety, Brevor, to give rise to the variety Gaines which was suitable for use with heavier applications of Nitrogen fertilizers. Seeds from the Norin10 x Brevor cross were also sent to Norman Borlaug in 1954, to introduce into the Mexican wheats, with almost immediate success, leading to the release of varieties Pitic and Penjamo in 1962 and Sonora in 1963. These varieties and their many successors spread like wildfire through the developing world and now occupy about 70% of its total wheat area.

• The breeding of dwarf rice for the subtropics followed a similarly prolonged and fortuitous route.

In rice there is only one widely-used dwarfing gene, which is recessive and inhibits production of the elongation hormone, gibberellic acid. In wheat there are more than ten ‘reduced height’ (Rht) genes, of which only three have been widely used. The two most widely used dwarfing genes, Rht1 and Rht2, came from Norin 10. Instead of blocking gibberellin production they confer insensitivity to it, whereas Rht8, which came from the Japanese wheat variety Akakomugi, blocks gibberellin synthesis. The Rht8 gene has long been used in Italian wheat breeding and varieties with it seem to be well adapted to East European conditions, whereas Rht1 and/or 2 have been used in all the ‘Mexican’ wheats and in breeding programmes throughout the Americas, Western Europe and Asia. So there may still be scope for a better-informed deployment of genes.

The dwarfing genes were introduced into rice and wheat to reduce lodging at higher rates of fertilizer use, i.e. to reduce yield losses. Subsequently, however, they have had an even greater, but largely unanticipated, impact on world food production by increasing the yield potential of wheat and rice, as we shall see in the next section. Both chance and design have played a part in their discovery and in their exploitation

8.3 The rise of the harvest index

The headlines of the late 1960s often referred to the transformation in world food supplies effected by ‘miracle rice’ and ‘the wonder wheats’ without specifying in what way they were miraculous or wonderful. Admittedly they did not fall over and lodge after heavy dressings of nitrogen fertilizers, but more that that was implied. They did not germinate sooner or grow faster, nor was their photosynthesis more efficient as sometimes suggested, so to what did they owe their superiority?

In 1962 a Dutch crop scientist, W.H. van Dobben, had shown that the substantial increase in yield of Dutch wheat varieties released between 1902 and 1961 was not accompanied by any increase in total crop weight but by a rise in the proportion of it in the grain, and therefore in yield. In 1920 the English crop scientist E.S. Beaven had called this proportion the ‘migration coefficient’ and had described the last stage of cereal crops as follows: ‘Some time … before the grain is ripe the plant ceases to gain weight … Its last effort is to transfer its accumulated reserves into the grain. But all, or very nearly all, the dry matter of the grain is first stored up in the leaves or stems of the plant … It is mainly … on the extent to which this ‘uplift’ takes place that plenty or scarcity of the staple food of man depends.’

That view of crop development may have been correct for the varieties and agronomy of the 1920s. But as the use of nitrogen fertilizers grew, and particularly if irrigation was available, varieties whose upper leaves remained green and active after flowering sere selected. Even by 1945 it was being suggested that most of the sugars required for grain growth came from ‘current account’ rather than from ‘savings’. In good wheat crops these days the reserves stored in the stem before flowering may contribute only 5% of grain weight, although rather more in rice.

• The proportion of total plant weight that ends up in the grain is now called the ‘harvest index’.
• For British wheat varieties in the 1920s the harvest index was about 35%; for modern varieties of both wheat and rice it is commonly 50-55%, having risen steeply since the dwarfing genes were introduced.

Clearly there are limits to how much further that rise – the source of recent increases in yield potential – can go. The harvest index depends also on the life span and growth habit of the crop. Although further dwarfing, e.g. with the more extreme Rht3 gene in wheat, is possible, it is likely that the harvest index of wheat and rice will not increase much beyond 60%. If so, we are approaching the end of the era of increasing yield potential via the harvest index, while remaining unsure of what other avenues can be exploited.

8.4 Silent Spring: The gathering storm