Feeding the Ten Billion Part 9

FEEDING THE TEN BILLION

PLANTS AND POPULATION GROWTH

L.T. EVANS

CAMBRIDGE UNIVERSITY PRESS                  1998

PART IX

8.4 Silent Spring: The gathering storm

In Silent Spring Rachel Carson wrote of the alienation between modern agriculture and nature: ‘Single crop farming does not take advantage of the principles by which nature works. Nature has introduced great variety into the landscape, but man has displayed a passion for simplifying it. Thus he undergoes the built-in checks and balances by which nature holds the species within bounds.’

• Carson’s primary focus was on the harm being done to wildlife, and possibly to human health, by the excessive and indiscriminate use of ‘the miracle insecticide’ DDT in agriculture, forestry and recreational public health programs.
• What Rachel Carson achieved was to bring the accumulating evidence of the harmful side-effects of modern insecticides together in a comprehensive and persuasive synthesis and, gently but insistently, to inject a sense of urgency into the issues.
• Clear Lake in California provided a telling example of the progressive concentration of DDT up the food chain, from 0.02 ppm in the water, through 5 ppm in plankton, 40-300 ppm in plant-eating fish, up to 2500 ppm in carnivorous species.
• Her most impressive chapter is that on the loss of birds, which gave the title to her book.
• In her final chapter, she urged the use of ‘the road less traveled’, of a more biological, less chemically-oriented approach to the control of agricultural pests and public health programs.
• She adds, however, ‘It is not my contention that chemical insecticides must never be used.’
• The ultimate outcome was the decision of the Environmental Protection Agency to ban all uses of DDT except those related to essential public health purposes.
• Within 30 years of its first use, therefore, the ‘miracle insecticide’ was banished from agriculture in most developed countries because of two of the characteristics which its discoverer had listed as essential in his Nobel lecture: wide range of action and long persistence.

 

8.5 The protein gap and high lysine maize

8.6 Latitude and the Green Revolution

8.7 The internationalization of agricultural research

Chapter 9: The Fifth Billion (1975-1986)

9.1 Introduction: resources and resourcefulness

Although the fifth billion was added to the world population in only 11 years, it began as a period of less apparent concern about world food supply. There were, of course, continuing pessimistic prognostications but, for the first time since the FAO gathered its statistics, the food supply per head in developing countries as a whole showed a sustained increase (14%) in spite of a 26% increase in population within 11 years. Reassuring also was the fact that this substantial increase in food production by the world as a whole did not require any increase in the area of arable land. There were small increases in South America (15%), Africa (4%) and Asia (0.5%) but these were offset by reductions in the more developed countries.

• The average yields of the staple cereals continued to rise over the 11-year period, reflecting the continuing impact of the dwarf cereals combined with a marked increase in the use of fertilizers in developing countries.
• The area under irrigation in developing countries increased by 82%, one consequence being that development debt repayments became increasingly burdensome for them.
• In the developed countries, the population increased by only 8.9% and food production had no problem keeping up.
• In fact, food surpluses were the problem in many developed countries, leading to reductions in publicly-funded agricultural research at the very time when, for the world as a whole, research was needed into ways of raising crop yield potentials after the full impact of the dwarfing genes is absorbed.
• Some of the Faustian bargains of high input agriculture became apparent during the accumulation of our fifth billion, and more biological approaches to the problems of agriculture, such as integrated pest management and the genetic engineering of plants were emphasized.

The oil price crisis of 1972/73 promoted a phase of intensive energy analysis of agriculture. This brought home the realization not only of how far we have traveled from the self-sufficient farmer but also of the extent to which modern agriculture is dependent on energy from fossil fuel. For the major crops, however, there is still a return in yield of 3-4 joules for each additional joule of input energy. But perhaps the most important lesson to be drawn from the energy analysis of agriculture derives from our being able to put all the inputs and outputs on a common scale, of energy. When this is done we find that, at least for rice in Asia, maize in the USA and wheat in France, diminishing returns to input energy even under the most intensive systems have so far been avoided.

• Diminishing returns may apply to some forms of agriculture, but they need not characterize agriculture in general.
• The energy analysis of agriculture gave a nudge to the development of minimum tillage just at the time when suitable herbicides became available.
• Apart from the savings in energy and manpower, and the greater flexibility and timeliness of minimum tillage, it can also permit the safe cultivation of steeper slopes, thereby increasing the potentially arable area.
• By making faster crop turn-around possible, it can also increase cropping intensity.
• Steps to stem genetic erosion led not only to their effective conservation, but also to a far wider concern for the preservation of global biodiversity, and the recognition of our wider evolutionary responsibility.
• The development of the techniques of genetic engineering within the period under discussion made the genes of the whole biosphere, from virus to mammal, potentially available for crop improvement.

Along with these advances there inevitably came new hazards. Earlier generations have often cursed their forebears for the disasters resulting from their lack of foresight. Our successors may well curse us likewise, but they should at least be aware of the many and diverse efforts of agriculturists and others to foresee the adverse future effects of the new agricultural technologies. However, as Winston Churchill once remarked: ‘It is always wise to look ahead, but difficult to look further than you can see.’

9.2 Energy use in agriculture

When the downward trend in real world prices for wheat and rice was sharply reversed by the oil supply crisis in 1973, the growing dependence of agriculture on off-farm sources of energy was suddenly highlighted. Energy analysis of agriculture became a growth industry.

The food sector generally accounts for 10-15% of total energy now used in industrialized countries, with only one fifth to one third of that proportion actually being used on-farm. In the USA, for example, about 17% of total energy use is for the food system, 6% for production and approximately equal amounts for packaging and for distribution. The consumption of energy on-farm has grown rapidly along with rises in yield as mechanization was extended and diversified, as the dependence on fertilizers, pesticides and herbicides increased and as grain drying and crop irrigation by pumps and sprays became more common. As Howard Odum put it: ‘Man no longer eats potatoes made from solar energy; now he eats potatoes partly made of oil.’

The classical analysis of changing energy use in agriculture was made by David Pimentel and his colleagues at Cornell on maize production in the USA, initially for six years between 1945 and 1970, but eventually extended to 1985. As is usual in such studies, the input of energy from the sun for crop growth was not included as a component of on-farm energy use because it would dwarf all the others, the intercepted solar energy being more than 95% of the total, considerably higher than Pimentel estimated it to be. On the output side the energy analyses stop at the farm gate, but they go upstream to include energy ‘embodied’ in the manufacture and transport of machinery, fertilizers, etc.

• Another convention of energy analysis concerns the farm workers: only the metabolic energy expended on their work is included, 5-8 megajoules per day.
• Rather different conclusions have been drawn from Pimentel’s studies depending on how the results were presented.
• If we simply plot the output energy against the input energy we find that, overall, the maize crops have continued to return at least 3 more joules in additional grain for each additional joule invested in the crop, and substantially more than that from 1975 to 1985.
• The most pronounced change in energy-input terms has been for nitrogenous fertilizers, which rose from 6.7% of the total in 1945 to 31% in 1985. The second largest energy-using component in 1985 was irrigation (22%), up from 5% in 1945. Other marked increases have been for herbicides and grain drying.

What the energy analysis of agriculture permits is the reduction of the great variety of inputs and outputs in modern agriculture to a common base, energy consumed and energy produced. And what this has shown us, unambiguously, is that at least for rice, wheat and maize, the three main staple crops of the world, yields per hectare can be increased many-fold without diminishing returns to non-solar energy consumption setting in.

• Modern agriculture is not prodigal of input energy, and next time you eat a slice of bread, please remember that much less energy was used in growing the wheat for it than in processing and distributing it for your convenience.

 

Minimum tillage systems

The scientific evidence in favour of reducing tillage and systems for achieving that, had been around for 30 years before the oil embargo crisis of the early 1970s pushed agriculture more decisively towards minimum tillage.

• When in 1943 an Ohio farmer, E.H. Faulkner, published Plowman’s Folly, in which he suggested the abandonment of ploughing in favour of discing, there was outrage and controversy but the movement towards minimum cultivation had begun.
• It had two strands: economy of labour and fuel, and the conservation of soil and water. These are reflected in the range of its names, including zero-till, conservation tillage, crop residue management, low energy systems of cultivation and the ecological approach to soil management.
• The key to the further development of minimum tillage was the introduction of herbicides effective enough to replace repeated cultivation for weed control.
• Along with herbicide improvement by the agrichemical companies there has been continuous development of farm machinery for minimum tillage, much of it by farmers themselves.
• Under conditions of adequate rainfall, soil water and drainage, crop yield has been shown not to be reduced by the reduction in tillage.
• Where rainfall and the opportunities for irrigation are limited, yields are often higher with reduced tillage, associated with better water penetration and conservation.
• On the other hand, yields may be lower in poorly drained situations or where there are problems with pest, disease or weed control.
• The reduction in soil erosion by minimum tillage can be striking, varying from 20- to 1000-fold across a range of environments.
• An important consequence of this effect is that soils of much greater slope can be safely cropped with minimum tillage provided the mulch can be conserved.
• On a world scale, the ability to cultivate steeper slopes safely implies a considerable increase in the area of potentially cultivable land.
• An equally valuable effect of minimum tillage, particularly at low latitudes, is the much faster turn-around between crops, thereby increasing the scope for multiple cropping.
• Another advantage of minimum tillage is that of more timely sowing, because the whole operation can be carried out over a wider range of soil moisture contents and not held up waiting for suitable conditions for ploughing.
• The greater speed of minimum tillage means that about four times more land can be prepared and sown by each cultivator.
• There are of course some disadvantages of minimum tillage. Some weeds are more difficult to control, as are some pests and diseases.

Minimum tillage has been called a ‘thing of the past, not a wave of the future’, but also ‘the greatest conservation practice of the 20^th century. Although minimum tillage was the outcome of the serendipitous discovery of growth-regulating herbicides, its development has combined the contributions of scientists, conservationists, farmers and the agrichemical industry to transform the central act of agriculture, the cultivation of the soil.

9.4 Genetic resources

9.5 integrated pest management: changing the paradigm