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RICE PADDIES (these are in Indonesia) provide the principal food for more than half the world's population. In many parts of Asia the terrain prevents farmers from using mechanized farm equipment; to grow and harvest a single acre of rice can demand more than 1,000 man-hours. Still, Asian countries now produce more than 90 percent of all rice grown.

Can the Growing Human Population Feed Itself?

John Bongaarts Scientific American Mar 94

Demographers now project that the world's population will double during the next half century, from 5.3 billion people in 1990 to more than 10 billion by 2050. How will the environment and humanity respond to this unprecedented growth? Expert opinion divides into two camps. Enviromnentalists and ecologists, whose views have widely been disseminated by the electronic and print media, regard the situation as a catastrophe in the making. They argue that in order to feed the growing population farmers must intensify agricultural practices that already cause grave ecological damage to our natural resources and the environment, now burdened by past population growth, will simply collapse under the weight of this future demand. The optimists, on the other hand, comprising many economists as well as some agricultural scientists, assert that the earth can readily produce more than enough food for the expected population in 2050. They contend that technological innovation and the continued investment of human capital will deliver high standards of living to much of the globe, even if the population grows much larger than the projected 10 billion. Which point of view will hold sway? What shape might the future of our species and the environment actually take? Many environmentalists fear that world food supply has reached a precarious state: "Human numbers are on a collision course with massive famines.... If humanity fails to act, nature will end the population explosion for us-in very unpleasant ways-well before 10 billion is reached," write Paul R. Ehrlich and Anne H. Ehrlich of Stanford University in their 1990 book The Population Explosion. In the long run, the Ehrlichs and like-minded experts consider substantial growth in food production to be absolutely impossible. "We are feeding ourselves at the expense of our children. By definition farmers can overplow and overpump only in the short run. For many farmers the short run is drawing to a close," states Lester R. Brown, president of the Worldwatch Institute, in a 1988 paper. Over the past three decades, these authors point out, enormous efforts and resources have been pooled to am pbfy agricultural output. Indeed, the total quantity of harvested crops increased dramatically during this time. In the developing world, food production rose by an average of 117 percent in the quarter of a century between 1965 and 1990. Asia performed far better than other regions, which saw increases below average. Because population has expanded rapidly as well, per capita food production has generally shown only modest change; in Africa it actually declined. As a consequence, the number of undernourished people is still rising in most parts of the developing world, although that number did fall from 844 million to 786 million during the 1980s. But this decline reflects improved nutritional conditions in Asia alone. During the same period, the number of people having energy-deftcient diets in Latin America, the Near East and Africa climbed. Many social factors can bring about conditions of hunger, but the pessimists emphasize that population pressure on fragile ecosystems plays a significant role. One specific concern is that we seem to be running short on land suitable for cultivation. If so, current efforts to bolster per capita food production by clearing more fertile land will find fewer options. Between 1850 and 1950 the amount of arable land grew quickly to accommodate both larger populations and greater demand for better diets. This expansion then slowed and by the late 1980s ceased altogether. In the developed world, as wen as in some developing countries (especially_ China), the area under cultivation started to decline during the1980s. This drop is largely because spreading urban centers have engulfed fertile land or, once the land is depleted, farmers have abandoned it. Farmers have also fled from irrigated land that has become unproductive because of salt accumulation. Moreover, environmentalists insist that soil erosion is destroying much of the land that is left.

The extent of the damage is the subject of controversy. A recent global assessment, sponsored by the United Nations Environment Program and reported by the World Resources Institute and others, offers some perspective. The study concludes that 17 percent of the land supporting plant Iife worldwide has lost value over the past 45 years. The estimate includes erosion caused by water and wind, as well as chemical and physical deterioration, and ranks the degree of soil degradation from light to severe. This degradation is least prevalent in North America (5.3 percent) and most widespread in Central America (25 percent), Europe (23 percent), Africa (22 percent) and Asia (20 percent). In most of these regions, the average farmer could not gather the resources necessary to restore moderate and severely affected soil regions to full productivity. Therefore, prospects for reversing the effects of sofl erosion are not good, and it is likely that tills problem win worsen.

Despite the loss and degradation of fertile land, the "green revolution" has promoted per capita food production by increasing the yield per hectare. The new, high-yielding strains of grains such as wheat and rice have proliferated since their introduction in the 1960s, especially in Asia. To reap full advantage from these new crop varieties, however, farmers must apply abundant quantities of fertilizer and water. Environmentalists question whether further conversion to such crops can be achieved at reasonable cost, especially in the developing world, where the gain in production is most needed. At the moment, farmers in Asia, Latin America and Africa use fertilizer sparingly, if at all, because it is too expensive or unavailable. Fertilizer use in the developed world has recently waned. The reasons for the decline are complex and may be temporary, but clearly farmers in North America and Europe have decided that increasing their already heavy application of fertilizer will not further enhance crop yields. Unfortimately, irrigation systems, which would enable many developing countries to join in the green revolution, are often too expensive to build. In most areas, irrigation is essential for generating higher yields. It also can make and land cultivable and protect farmers from the vulnerability inherent in natural variations in the weather. Land brought into cultivation tills way could be used for growing multiple crop varieties, thereby helping food production to increase. Such advantages have been realized since the beginning of agriculture: the earliest irrigation systems are thousands of years old. Yet only a fraction of productive land in the developing world is now irrigated, and its expansion has been slower than population growth. Consequently, the amount of irrigated land per capita has been dwindling during recent decades. The trend, pessimists argue, will be hard to stop. Irrigation systems have been built in the most affordable sites, and the hope for extending them is curtailed by rising costs. Moreover, the accretion of silt in dams and reservoirs and of salt in already irrigated soil is increasingly costly to avoid or reverse.

Environmentalists Ehrlich and Ehrlich note that modern agriculture is by nature at risk wherever it is practiced. The genetic uriiforniity of single, high-yielding crop strains planted over large areas makes them highly productive but also renders them particularly vulnerable to insects and disease. Current preventive tactics, such as spraying pesticides and rotating crops, are only partial solutions. Rapidly evolving pathogens pose a continuous challenge. Plant breeders must maintain a broad genetic arsenal of crops by collecting and storing natural varieties and by breeding new ones in the laboratory.

The optimists do not deny that many problems e)dst within the Tfood supply system. But many of these authorities, including D. Gale Johnson, the late Herman Kahn, Walter R. Brown, L. Martel, the late Roger Revelle, Vaclav Smfl and Julian L. Simon, believe the world's food supply can dramatically be expanded. Ironically, they draw their enthusiasm from extrapolation of the very trends that so alarm those experts who expect doom. In fact, statistics show that the average daily caloric intake per capita climbed by 21 percent (from 2,063 calories to 2,495 calories) between 1965 and 1990 in the developing countries. These higher calories have generally delivered greater amounts of protein. On average, the per capita consumption of protein rose from 52 grams per day to 61 grams per day between 1965 and 1990. According to the optimists, not only has the world food situation improved significantly in recent decades, but further growth can be brought about in various ways. A detailed assessment of climate and soil conditions in 93 developing countries (excluding China) shows that nearly three times as much land as is currently farmed, or an additional 2.1 billion hectares, could be cultivated. Regional sod estimates indicate that sub-Saharan Africa and Latin America can exploit many more stretches of unused land than can Asia, the Near East and North Africa.

INCIDENCE OF CHRONIC UNDERNUTRITION fell in the developing world from an estimated 844 million sufferers in 1979 to 786 million in 1990, showing evidence of dramatic nutritional improvements in Asia (left). Agricultural productivity must improve to continue this trend (right). Even if more land is harvested in 205O, the average yield must rise sharply as well to offer the projected Third World population of 8.7 billion the current diet of 4,000 gross calories per day.

Even in regions where the amount of potentially arable land is limited, crops could be grown more times every year than is currently the case. This scenario is particularly true in the tropics and subtropics where conditions are suchrelatively even temperature throughout the year and a consistent distribution of daylight hours-that more than one crop would thrive. Nearly twice as many crops are harvested every year in Asia than in Africa at present, but further increases are possible in all regions. In addition to multicropping, higher yields per crop are attainable, especially in Africa and the Near East. Many more crops are currently harvested per hectare in the First World than elsewhere: cereal yields in North America and Europe averaged 4.2 tons per hectare, compared with 2.9 in the Far East (4.2 in China), 2.1 in Latin America, 1.7 in the Near East and only 1.0 in Africa. Such yield improvements, the enthusiasts note, can be achieved by expanding the still limited use of high-yield crop varieties, fertilizer and irrigation.

The Potential Impact of GlobalWarming on Agriculture

The scientific evidence on the greenhouse effect indicates that slow but significant global warming is likely to occur if the emission of greenhouse gases, such as carbon dioxide, methane, nitrogen oxide and chlorofluorocarbons, continues to grow. Agriculture is directly or, at least in some cases, indirectly responsible for releasing a substantial proportion of these gases. Policy responses to the potentially adverse consequences of global climatic change now focus primarily on hindering emissions rather than on halting them. But considering the present need to improve living standards and produce more food for vast numbers of people, experts doubt that even a reduction in global emissions could occur in the near future. In a 1990 study the Inter-governmental Panel on Climate Change estimated that over the next century the average global temperature will rise by three degrees Celsius. The study assumes that agriculture will expand considerably. This forecast of temperature change is uncertain, but there is now broad agreement that some global warming will take place. All the same, the effect that temperature rise will have on human society remains an open question. Global warming could either enhance or impede agriculture, suggest Cynthia Rosenzweig of Columbia University and Martin L. Parry of the University of Oxford. Given sufficient water and light, increased ambient carbon dioxide concentrations absorbed during photosynthesis could act as a fertilizer and facilitate growth in certain plants. In addition, by extending the time between the last frost in the spring and the first frost in the fall, global warming will benefit agriculture in cold regions where the growing season is short, such as in Canada and northern areas of Europe and the former Soviet Union. Moreover, warmer air holds more water vapor, and so global warming will bring about more evaporation and precipitation. Areas where crop production is limited by arid conditions would benefit from a wetter climate. If increased evaporation from soil and plants does not coincide with more rainfall in a region, however, more frequent dry spells and droughts would occur. And a further rise in temperature will reduce crop yields in tropical and subtropical areas, where certain crops are already grown near their limit of heat tolerance. Furthermore, some cereal crops need low winter temperatures to initiate flowering. Warmer winters in temperate regions could therefore stall growing periods and lead to reduced harvests. Finally, global warming will precipitate a thermal swelling of the oceans and melt polar ice. Higher sea levels may claim low-lying farmland and cause higher salt concentrations in the coastal groundwater.

Techniques used to model the climate are not sufficiently advanced to predict the balance of these effects in specific areas. The most recent analysis on the impact of climatic change on the world food supply, by Rosenzweig and Parry in 1992, concludes that average global food production will decline 5 percent by 2060. And they anticipate a somewhat larger drop in the developing world, thus exacerbating the problems expected to arise in attempts to feed growing populations. In contrast, their report predicts a slight rise in agricultural output in developed countries situated at middle and high latitudes.

In World Agriculture: Toward 2000, Nikos Alexandratos of the Food and Agriculture Organization (FAO) of the United Nations reports that orily 34 percent of all seeds planted during the mid-1980s were high-yielding varieties. Statistics from the FAO show that at present only about one in five hectares of arable land is irrigated, and very little fertilizer is used. Pesticides are sparsely applied. Food output could drastically be increased simply by more widespread implementation of such technologies. Aside from producing more food, many economists and agriculturalists point out, consumption levels in the developing world could be boosted by wasting fewer crops, as well as by cutting storage and distribution losses. How much of an increase would these measures yield? Robert W. Kates, director of the Alan Shawn Feinstein World Hunger Program at Brown University, writes in The Hunger Report: 1988 that humans consume only 60 percent of all harvested crops, and some 25 to 30 percent is lost before reaching individual homes. The FAO, on the other hand, estimates lower distribution losses: 6 percent for cereals, 11 percent for roots and 5 percent for pulses. All the same, there is no doubt that improved storage and distribution systems would leave more food available for human nutrition, independent of future food production capabilities. For optimists, the long-range trend in food prices constitutes the most convincing evidence for the correctness of their view. In 1992-93 the World Resources Institute reported that food prices dropped further than the price of most nonfuel commodities, an of which have declined in the past decade. Cereal prices in the intemational market fell by approximately one third between 1980 and 1989. Huge govemment subsidies for agriculture in North America and Western Europe, and the resulting surpluses of agricultural products, have depressed prices. Obviously, the optimists assert, the supply already exceeds the demand of a global population that has doubled since 1950. Taken together, this evidence leads many experts to see no significant obstacles to raising levels of nutrition for world populations exceeding 10 billion people. The potential for an enormous expansion of food production exists, but its realization depends of course on sensible governmental policies, increased domestic and international trade and large investments in infrastructure and agricultural extension. Such improvements can be achieved, the optimists believe, without incurring irreparable damage to global ecosystems.

TOTAL FOOD PRODUCTION rose nearly 120 percent between 1965 and 1990 in the developing world. Per capita food production showed little change in regions outside Asia (top). Son erosion has debased much of the land worldwide on which that food was produced (middle). But many Third World nations have vast holdings that could be farmed successfully if given more water and fertilizer (bottom).

Proponents of either of these conflicting perspectives have difficulty accepting the existence of other plausible points of view. Moreover, the polarity between the two sides of expert opinion shows that neither group can be completely correct. Finding some common ground between these seemingly irreconcilable positions is not as difficult as it at first appears if empirical issues are emphasized and important differences in value systems and political beliefs are ignored. Both sides agree that the demand for food will swell rapidly over the next several decades. In 1990 a person living in the developing world ate on average 2,500 calories each day, taken from 4,000 gross calories of food crops made available within a household. The remaining 1,500 calories from this gross total not used to meet nutritional requirements were either lost, inedible or used as animal feed and plant seed. Most of this food was harvested from 0.7 billion hectares of land in the developing world. The remaining 5 percent of the total food supply came from imports. To sustain this 4,000-gross-calorie diet for more than twice as many residents, or 8.7 bilhon people, living in the developing world by 2050, agriculture must offer 112 percent more crops. To raise the average Third World diet to 6,000 gross calories per day, slightly above the 1990 world average, food production would need to increase by 218 percent. And to bring the average Third World diet to a level comparable with that currently found in the developed world, or 10,000 gross calories per day, food production would have to surge by 430 percent. A more generous food supply will be achieved in the future through boosting crop yields, as it has been accomphshed in the past. if the harvested area in the developing world remains at 0.7 billion hectares, then each hectare must more than double its yield to maintain an already inadequate diet for the future population of the developing world. Providing a diet equivalent to a First World diet in 1990 would require that each hectare increase its yield more than six times. Such an event in the developing world must be considered virtually impossible, barring a major breakthrough in the biotechnology of food production. Instead farmers will no doubt plant more acres and grow more crops per year on the same land to help augment crop harvests. Extrapolation of past trends suggests that the total harvested area wfll increase by about 50 percent by the year 2050. Each hectare will then have to provide nearly 50 percent more tons of grain or its equivalent to keep up with current dietary levels. Improved diets could result ortly from much larger yields. The technological optimists are correct in stating that overall world food production can substantially be increased over the next few -decades. Current crop yields are well below their theoretical maxima, and only about 11 percent of the world's formable land is now under cultivation. Moreover, the experience gained recently in a number of developing countries, such as China, holds important lessons on how to tap this potential elsewhere. Agricultural productivity responds to well-designed policies that assist farmers by supplying needed fertilizer and other inputs, building sound infrastructure and providing market access. Further investments in agricultural research will spawn new technologies that will fortify agriculture in the future. The vital question then is not how to grow more food but rather how to implement agricultural methods that may make possible a boost in food production. A more troublesome problem is how to acmeve this technological enhancement at acceptable environmental costs. It is here that the arguments of those experts who forecast a catastrophe carry considerable weight. There can be no doubt that the land now used for growing food crops is generally of better quality than unused, potentially cultivable land. Siniflarly, existing irrigation systems have been built on the most favorable sites. Consequently, each new measure applied to increase yields is becoming more expensive to implement, especially in the developed world and parts of the developing world such as China, where productivity is already Wgh. In short, such constraints are raising the marginal cost of each additional ton of grain or its equivalent. This tax is even higher if one takes into account negative extemalities-primarily environmental costs not reflected in the price of agricultural products. The environmental price of what in the Ehrlichs' view amounts to "turning the earth into a giant human feedlot" could be severe.

EGYPTIAN FARMERS, advised by Israeli agronomists, have converted more thaia 400,000 acres of desert soil into rich cropland by implementing irrigation systems. Farms in Nubariya now produce ample harvests of fruit.

A large inflation of agriculture to provide growing populations with improved diets is likely to lead to widespread deforestation, loss of species, sofl erosion and pollution from pesticides, and runoff of fertilizer as farming intensifies and new land is brought into production. Reducing or niininiizing tills environmental impact is possible but costly. Given so many uncertainties, the course of future food prices is difficult to chart. At the very least, the rising marginal cost of food production will engender steeper prices on the international market than would be the case if there were no environmental constraints. Whether these Wgher costs can offset the historical decline in food prices remains to be seen. An upward trend in the price of food sometime in the near future is a distinct possibility. Such a hike wffl be mitigated by the continued development and application of new technology and by the likely recovery of agricultural production and exports in the former Soviet Union, eastern Europe and Latin America. Also, any future price increases could be lessened by taking advantage of the under-utilized agricultural resources in North America, notes Per Pinstrup-Andersen of Cornell University in Ws 1992 paper "Global Perspectives for Food Production and Consumption." Rising prices will have little effect on high-income countries or on households possessing reasonable purchasing power, but the poor will suffer. In reality, the future of global food production is neither as grim as the pessimists beheve nor as rosy as the optimists claim. The most plausible outcome is that dietary intake will creep higher in most regions. Significant annual fluctuations in food availability and prices are, of course, likely; a variety of factors, including the weather, trade interruptions and the vulnerability of monocropping to pests, can alter food supply anywhere. The expansion of agriculture will be achieved by boosting crop yields and by using existing farmland more intensively, as well as by bringing arable land into cultivation where such action proves econoniical. Such events will transpire more slowly than in the past, however, because of environmental constraints. In addition, the demand for food in the developed world is approaching saturation levels. In the U.S., mounting concerns about health have caused the per capita consumption of calories from animal products to drop.

Still progress will be far from uniform. Numerous countries will struggle to overcome unsatisfactory nutrition levels. These countries fall into three main categories. Some low-income countries have little or no reserves of fertile land or water. The absence of agricultural resources is in itself not an insurmountable problem, as is demonstrated by regions, such as Hong Kong and Kuwait, that can purchase their food on the international market. But many poor countries, such as Bangladesh, cannot afford to buy food from abroad and thereby compensate for insufficient natural resources. These countries will probably rely more on food aid in the future.

Low nutrition levels are also found in many countries, such as Zaire, that do possess large reserves of potentially cultivable land and water. Govermnent neglect of agriculture and policy failures have typically caused poor diets in such countries. A recent World Bank report describes the damaging effects of direct and indirect taxation of agriculture, controls placed on prices and market access, and overvalued currencies, which discourage exports and encourage imports. Where agricultural production has suffered from niisguided government intervention (as is particularly the case in Africa), the solution-policy reform-is clear. Food aid will be needed as well in areas rife with political instability and civil strife. The most devastating famines of the past decade, known to television viewers around the world, have occurred in regions fighting prolonged civil wars, such as Ethiopia, Somalia and the Sudan. In many of these cases, drought was instrumental in stirring social and political disruption. The addition of violent conflict prevented the recuperation of agriculture and the distribution of food, thus turning bad but remediable situations into disasters. International military intervention, as in Somalia, provides only a short-term remedy. In the absence of sweeping political compromise, hunger and malnutrition will remain endemic in these war-torn regions.

Feeding a growing world population a diet that improves over time in quality and quantity is technologically feasible. But the economic and enviromnental costs incurred through bolstering food production may well prove too great for many poor countries. The course of events will depend crucially on their governments' ability to design and enforce effective policies that address the challenges posed by mounting human numbers, rising poverty and environmental degradation. Whatever the outcome, the task ahead win be made more difficult if population growth rates cannot be reduced.