There is another part of the equation relating food production and population growth that remains a puzzle: how much food, and how varied a diet, is required for each member of the population? This is not a topic on which I can claim any authority. Nevertheless, I feel that it merits attention in relation to future perspectives. There is now an extensive literature, provoked initially in regard to protein, following the large reductions in the FAO figures for essential quantities required, spurred by John Waterlow's work at the Rowett Institute in Aberdeen. The debate on protein quality, and the need for high levels of animal rather than vegetable protein, has distorted the discussions of food security for many years and is still not finally resolved (Waterlow et al., 1998). I will not rehearse the arguments here, other than to say that livestock produce about 30% of current food consumption, and that it is important that the need for this is recognized. The success of the early semidwarf, high yielding varieties of rice and wheat was such that many nutritionists feared that a serious "protein gap" would emerge, because increases in carbohydrates would not be balanced by increases of protein. Both the amounts of protein and its quality in terms of essential amino acids present were queried. More careful analysis of the problem has subsequently shown that many aspects required further attention (McLaren, 1974; Waterlow and Payne, 1975; Young, 1997). Livestock products account for more than half of current protein and essential amino acid needs. Thus, for a balanced diet it appears at present that it is important that there is an increase in animal foodstuffs as well as cereals and root crops. Changing to a vegetarian diet, as has been advocated by some, appears not to be an answer to the food security problem, and falling production of pulses and other high-protein crops suggests that a different answer must be sought.
Much more land is required to produce equivalent quantities of calories from meat and milk than from cereals, so that there is a significant disadvantage to animal-based diets in terms of quantities of land required, although there are advantages when food quality is considered. Fitzhugh (1998), director general of the International Livestock Research Institute (ILRI), also believes that the land required for animal production has tended to be overestimated, because much land used for animal production is rough grazing, unsuited to arable use.
Fortunately, much can be done to improve the quality of higher-yielding cereal varieties. In the course of the next two decades, adjustments in diets to bring them more in line with real human nutritional needs may become more important than the simple increase in food production. IRRI's original mandate was often simply expressed by Nyle Brady as "more rice." In the last 20 years, that has changed to "more rice with fewer adverse environmental effects." In the course of the next 20 years that may well change to "more rice of more appropriate nutritional value."
The first steps toward that end may well have been taken in the breeding of "golden rice" (Potrykus, 2001) in which genetic engineering has been used to enhance vitamin A content. Release by the International Centre for the Improvement of Maize and Wheat (CIMMYT) of high-protein maize varieties is another example of the route to better diets that will change the need for additional land resources. However, a major advance in education regarding human nutrition will be needed before such dietary changes will be accepted by the public. But as a greater understanding of the relationship between food and body size and shape is gained, people should be better able to understand what they should eat, and how much is necessary. At the present time, dietary requirements are based on old estimates that around 2,500 calories per person per day are needed. This is still well below current U.S. and European consumption.
The importance of global food security seems largely to be forgotten at the present time, with most developed countries more concerned with profitable disposal of surpluses than with the reduction of hunger in the Third World. African calamities continue to occur, as in Rwanda, Ethiopia, and much of Southern Africa where there has been below-average rainfall for several years. But while the majority of those living outside Africa see increases in population numbers as a major hindrance to African economic development, that view is not shared by all African scientists.
At the conference on population organized in India by the Royal Society in association with 60 other national academies in 1994, the final recommendation was that demographic increases should be minimized, and that a path to greater food production must be found that respects the environment and natural resources as well as economic, social, and cultural conditions (Graham-Smith, 1994). But there were two dissenting voices. One that could have been anticipated came from the Vatican, concerned by the prominence given to the need for birth control. Sadly the other came from the African academies of science. They added their own amendment, which stated that "care must be taken to acknowledge that while current rates of population growth and even absolute rates of (increase in) population sizes may be and are a problem for particular countries, for Africa population remains an important resource for development without which the continent's natural resources will remain latent and unexplored." And "[w]hether or not the earth is finite will depend on the extent to which science and technology (are) able to transform the resources available to humanity" (Graham-Smith, 1994:391).
We should pause here to consider for a moment the time scales of the perspectives of different writers. As noted earlier, the main theme of Malthus' essay was that population increases by a geometrical progression, but food supply increases arithmetically. Therefore, at some point population numbers must exceed food supply. The examples Malthus used were mostly of events within living memory, and so the timescale he was considering was that of a human lifetime. Politicians' timescales are largely limited to the days or months to the next election, whereas scientists' timescales tend to be much longer. Hence, in drawing attention to the problems of food security, scientists are mostly struggling to convince politicians of the immediacy of the need to provide further financial support.
As noted earlier, had Malthus consulted more widely among the scientists of his time he might have been less adamant in his arguments. Better and more scientifically based opinions about the potential to increase food production were becoming available. And the success of John Lawes' superphosphate factory opened in London in 1840 provided excellent evidence of the potential to increase food production. Nevertheless, Malthus recognized the importance of improvements in crop production methods. For example, he praised the industry of the Chinese peasants in manuring, watering, and cultivating their land. But in spite of their efforts, the pressure of population in the Yangzi Valley was the major contributor to the causes of the Taiping Wars. Between 1850 and 1867, more than 30 million died, and much of the infrastructure created to support rice production was destroyed (Ho Ping-ti, 1959). Remedies proposed and used included infanticide, at least of female children, compulsory sterilization, and heavy taxation of families having more than one child. In spite of the continued use of some of these drastic measures by recent communist governments, the Chinese population has continued to grow, and is now believed to exceed 1.3 billion.
Tim Dyson concludes his recent book, Population and Food: Global Trends and Future Prospects, with a section headed "Tempered Hope." He suggests that "there is fair reason to expect that in the year 2020 world agriculture will be feeding the larger global population no worse — and probably a little better — than it manages to do today." Just over a decade ago there was serious concern that the "population momentum" created by the dominant numbers of women of childbearing age would lead to a surge in the rate of population growth. In fact, there has been a significant decrease, to which AIDS and warfare have made only small contributions. Of the problems recognized by Dyson (1996), Evans (1993, 1998), and Hillel (1991), it is perhaps most difficult to predict how fast changes in climate are likely to proceed, and what can be done about them. We do not know how far human activity is to be blamed as the causal agent of the current phase of climate warming. Reduction of emissions of carbon dioxide and methane and nitrous oxide may help to slow the rate of change, and there is still hope for much to be done to increase carbon sequestration, as Lal et al. (1995a, 1995b, 1998, 1999) have shown, but if the effects of the tilt of the earth are the main cause, changes in human activities may have little influence. Immediate and long-term effects on food production are difficult to predict, particularly the balance between warming of the colder regions to allow cereal production to be extended, and increasingly frequent drought in many warmer regions, causing major losses of productivity.
But at the same time, the population growth rate has slowed significantly. Personally, I believe that the major contribution to this recent decrease has come from better education. Various threats to food security remain, and not least are those posed by political factors related to access to water and oil, and the long-term problems associated with continuing soil degradation. To these I would add the threat that comes from present-day disbelievers in sound science, who, at least in the United Kingdom, receive too much favorable publicity in the press.
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