Feeding the Ten Billion Part 13

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FEEDING THE TEN BILLION

PLANTS AND POPULATION GROWTH

L.T. EVANS

CAMBRIDGE UNIVERSITY PRESS                  1998

PART XIII

Chapter 12: Feeding the Ten Billion

12.1 Introduction: routes to greater food production

  • The world must develop the capacity to feed the ten billion within the next 40-50 years, predominantly within Asia and Africa. There are two quite separate but often conflated problems.
  • The first is that of developing the global capacity to produce enough food for ten billion people, i.e. for 67% more than at present, the main focus of this book.
  • The second is that of eliminating the chronic undernutrition which still afflicts so many of us in a world which produces enough food for all.
  • Agricultural research is the key to the first problem but cannot be expected to solve the second, more complex, task of eliminating poverty and providing the work, health and education which should allow the poor to obtain food.
  • The six main components of increased global food supply by crops are:
  • Increase in the area under cultivation
  • Increase in yield per hectare per crop
  • Increase in the number of crops per hectare per year
  • Displacement of lower yielding crops by higher yielding ones
  • Reduction of post harvest losses
  • Reduced use as feed for animals
  • Although new land is being brought into cultivation, gains have been balanced by losses to the spread of cities and infrastructure and to erosion and degradation.
  • Since 1960, increase in yield per crop has been the dominant component of greater food production, but high input agriculture inevitably generates new problems and concerns.
  • Increase in the number of crops per year from a given piece of arable land mostly requires access to irrigation as well as high input use and the breeding of short season varieties.
  • The displacement of less productive by more productive crops has been going on since the beginning of domestication.
  • The scope for reducing post-harvest losses remains unclear.
  • A radical change in the consumption of animal products in our diets could have a huge impact on the amount of grain available globally for direct human consumption.
  • The following sections consider some of the factors bearing on these routes to greater food production.

 

12.2 Will there be enough arable land

Until the world population reached three billion, extension of the area under cultivation was the main source of global food production. Then, quite suddenly, that expansion slowed and the present area of arable land, 1.34 billion hectares, about 11% of the land surface not covered by ice, is only slightly greater than it was in 1960.

  • The recent stasis in arable area is not because the world has run out of potentially arable land. Far from it. Several independent estimates indicate that between 3.0 and 3.4 billion hectares (ha) of land are potentially cultivable.
  • Once the rise in the average world yields of the staple cereals began to keep pace with population there was less pressure for further extension of the arable area.
  • The crucial role of higher input agriculture in making possible the conservation of otherwise threatened natural communities is not always appreciated.
  • The intensification of agriculture and the raising of yields was essential, as well as timely, besides saving about 1.8 billion ha from the plough.
  • As crop yields are raised by the intensification of agriculture, the amount of arable land needed to supply each person falls.
  • The apparent stability of the area under cultivation on a world scale conceals some disturbing trends in both the losses and the compensating gains.
  • The most serious loss is that to urbanization which now exceeds, and occupies much of, what was the arable area of the world in AD 1700. Cities tend to grow on the best agricultural land.
  • When we turn to losses of arable land by erosion, desertification, salination, toxification and other forms of mismanagement, the many estimates vary wildly.
  • Buringh and Dudal estimate that each year since 1975 about 2 M ha of arable land have been seriously toxified; another 2 M ha desertified; and 8 M ha converted to non-agricultural use.
  • The total of 12 M ha per year represents a loss of almost 1% of arable land each year.
  • On top of these losses of land from cultivation there are also the losses in the productive capacity of the remaining arable land.
  • One recent survey suggests that 38% of our cropland has been degraded to some extent over the last 50 years, another 47% of the rainfed drylands and 30%  of irrigated drylands have been degraded.

In projections forward to AD 2010, further increases of about 30% in arable area of sub-Saharan Africa and Latin America are anticipated by FAO, compared with only 4% in south Asia and 9% in the near east/North Africa region. Thus increase in arable area is expected to play a relatively minor role in the further expansion of world food production, but significant extension of the arable to less favoured soils and environments will be needed to replace urbanized or degraded areas. The conservation and improvement of already cultivated soils should rank high in our priorities, but is not always feasible or economic when farms are small or grain prices low.

12.3 Intensification

Ester Boserup’s thesis that population pressure drives the intensification of agriculture grew out of her observation of the progressive shortening of the fallow period in shifting cultivation from forest (20-25 years) to bush (6-10 years) to grass (1-2 years) to annual and then multiple cropping. Such progressive intensification in response to rising population pressure occurred in Europe and China in earlier times and is still to be seen in Africa, South America and Asia.

Where soil fertility cannot be maintained by means other than fallow, yields and the returns on labour will decline with intensification. As this proceeds, greater nutrient input is required and, once the stage of grazing animals on pasture leys as a source of farmyard manure is passed, this must come from legume crops in a rotation or from fertilizers. Still further intensification requires still heavier applications of progressively more nutrients to replace those removed by the crops.

More crops also require more water, so supplementary and eventually full irrigation may be needed. As cropping becomes more intensive and the diversity of crops is reduced, weed, pest and disease problems become more acute, requiring further inputs. More labour is also needed to tend the crops, which can provide more opportunities for the poor and landless to earn income, and raise real wages even in densely populated, labour-surplus countries such as India. However, the incentives to still further intensification may be lessened for the farmers.

  • Of the currently arable land in developing countries, only in Asia does the average intensity of cropping currently exceed more than one crop per year.
  • Much of the uncropped arable land is in drier areas. Thus, there may be little scope for fuller use of the already arable land in developing countries except where irrigation is possible.

Double cropping of rice has been known in China since Sung times (12th century AD) and has spread progressively northwards. The key to it was the introduction of the early flowering Champa rices, together with irrigation and transplanting. In much of China and other irrigated areas such as the Punjab, the cropping intensity now approaches an average of 2, and could go still higher as even earlier maturing varieties with high yield potential are bred. Rice is particularly well suited to it and one sixth of the global area under rice is double cropped. More diverse systems, such as wheat-rice rotations, have been developed, and further improvements in tillage, fertilizer use and varietal characteristics – especially early maturity – could raise the cropping intensity still further.

  •  The availability of irrigation water may prove to be the limiting factor to intensification.
  • At the International Rice Research Institute in the Philippines three crops of rice per year have been grown on one field without interruption for 34 years.

 

12.4 The imperative of further increase in yield

Increase in the average yields of the cereal staples has largely kept pace with the increase in world population since 1960 and it is widely assumed that it will continue to do so until the population begins to stabilize in the 21st century. Between 1966 and 1990 the rate of increase in grain production was 1.87% per year and increase in yield has accounted for 92% of this since 1974.

  • But can a continuing and sufficient rise in yield per crop be taken for granted as so many economists and demographers seem to assume?
  • World cereal yield would have to reach at least 4.0 tonnes per ha for a population of 8 billion, and 5.0 tonnes per ha for a population of 10 billion, from its present level of 3.0 tonnes per ha.
  • Even for 8 billion people, the average world yield would have to equal those of Europe and North America today, and exceed them by more than 25% to sustain 10 billion.
  • Undoubtedly there is still some momentum, at least in many developing countries, for further increases in yield from the innovations of the Green Revolution.
  • The earlier chapters of this book have shown us over and over again that there are no grounds for assuming there will not be further advances in yield just because we cannot foresee a route to them.
  • Nevertheless, the conjunction of three innovations (cheap nitrogenous fertilizers, dwarf cereals and improved weed control) which gave the Green Revolution such a timely impact on world food production, may prove to be unique.
  • Further increases in the harvest index will be limited and other sources of greater yield potential, such as faster photosynthesis or growth, do not seem imminent.

However, crop yields could go on increasing to a significant extent even in the absence of any further rises in yield potential, for several reasons. The yield potential is the yield of a cultivar when it is grown in environments to which it is adapted, with nutrients and water non-limiting, and with pests, diseases, weeds, lodging and other stresses effectively controlled. Actual yields are mostly far below that potential because of imperfect adaptation to local environments, insufficient provision of nutrients and water, and incomplete control of pests, diseases and weeds. There is also considerable scope for further investment in land improvement through drainage, terracing, control of acidification, etc. where these have not already been introduced. Such investments have often been subsidized by governments in developed countries, and may require targeted aid to developing countries.

  • Thus, yields may well be raised even if yield potential is not. But whether they can be doubled, on average, over the next 50 years or so without further raising the yield potential is open to question.

 

12.5 The resources for future food production

René Dubos once said, provocatively: ‘There are no resources, only human resourcefulness.’ The crucial role of further rises in crop yields in the absence of further expansion of the arable has just been highlighted. Such rises will come partly from plant breeding and partly from agronomic improvements which will depend, in turn, on the greater use of other resources as substitutes for land. The most important of these are irrigation water, fertilizer elements and sources of energy, and it is these that may eventually limit the world’s capacity for food production.

Although less than one fifth of the world’s arable land is irrigated, that small fraction has contributed most of the increase in wheat and rice production by developing countries in recent years. As the key to higher yields and greater cropping intensity in developing countries, the further extension of irrigation is essential, but likely to be limited, for several reasons.

  • Firstly the demands of industry and urban areas for water are growing rapidly, and they are better able to pay for it.
  • Secondly, much of the most readily available water and land suitable for irrigation has already been tapped and the cost of new irrigation developments is rising.
  • Thirdly, irrigation has been given a poor image in recent years, with too much emphasis on its environmental problems, from salination to schistosomiasis, and too little on its crucial role in feeding the world.
  • The control of water resources may well prove to be a defining issue for the 21st century.
  • The supply of fresh water for irrigation could be augmented if a source of cheap energy for desalination of seawater and pumping and distribution inland is developed.

We have already seen how human labour and animal power have been replaced and augmented in modern agronomy by mechanization, electrification and the industrial production of an increasing variety of inputs. Energy supply will continue to be a major component of future agricultural development and may become the primary limitation to it insofar as it is the key to enhancing resources of water, arable land, mineral nutrients and other inputs. As Vasey puts it: ‘Food futures hinge on population and energy futures.’ Agriculture currently consumes only about 5% of the world’s energy use, nearly all of it based on non-renewable fossil fuel. In that respect modern agriculture is not as sustainable as it was until there were only two billion of us.

Repetto argues that agriculture will be truly sustainable only when it relies on Nature’s income, not on its capital. While there may be limited scope for liquid fuel crops, agriculture could not possibly produce both the input energy it needs and the food needed by the ten billion. Although agriculture cannot achieve Repetto’s goal, however, more than 99% of the total energy intercepted by or applied to high yielding maize crops sill comes directly from the sun, not from fossil fuels. What the other inputs achieve is a greater efficiency in converting that intercepted solar energy into food.

12.5 Old and new crops

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