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Proc. Natl. Acad. Sci. USA Vol. 96, pp. 5915-5920, May 1999 Colloquium Paper This paper was presented at the National Academy of Sciences colloquium "Plants and Population: Is There Time?" held December 5-6, 1998, at the Arnold and Mabel Beckman Center in Irvine, CA. The growth of demand will limit output growth for food over the next quarter century D. GALE JOHNSON Department of Economics, University of Chicago, 1126 East S9th Street, Chicago, IL 60637 ABSTRACT The rate of growth of world food demand will be much slower for 1990-2010 than it was for the prior three decades. The major factor determining the increase in food demand is population growth. Income growth has a much smaller effect. From 1960 to 1990, population growth accounted for approximately three fourths of the growth in demand or use of grain. For 1990-2010, it is anticipated that population growth will account for nearly all of the increase in world demand for grain. The rate of population growth from 1990 to 2020 is projected to be at an annual rate of 1.3% compared with 1.9% for 1960 to 1990 a decline of more than 30%. World per capita use of grain will increase very little perhaps by 4%. The increase in grain use is projected to be 40% less than in 1960-1990. It is anticipated that real grain prices will decline during the period, although not nearly as much as the 40~o decline in the previous three decades. Concern has been expressed concerning the dete- rioration of the quality and productivity of the world's farmland. A study for China and Indonesia indicates that there has been no significant change in the productive capacity of the land over the past 50 years. Contrary to numerous claims, the depth of the topsoil has not changed, indicating that erosion has had little or no impact. The past half century has witnessed an unparalleled im- provement in the per capita consumption of food in the world. The improvement has occurred in both the developed and, with the exception of sub-Saharan Africa, developing regions. In the case of sub-Saharan Africa, the failure to achieve a significant increase in per capita food supplies has been due, not primarily to limitations of natural resources, but to wholly inappropriate national policies that exploited agriculture in the name of promoting economic development as well as by ethnic and civil strife in several countries. A World Bank study of the effects of governmental interven- tion found for 1960-1984 that for three countries in sub- Saharan Africa the returns received by farmers were reduced by 51.6% (1~. This meant that farmers received less than half what they would have received had their prices been at the international price levels, with adjustment for local costs of marketing and transportation. The study considered both direct interventions, such as export taxes, and indirect ones, such as overvalued currencies and industrial tariff protec- tion. It was estimated that if farmers had received the international market prices (i.e., the governmental interven- tions were removed) that output would have increased by 57% (2~. This result assumed a period of adjustment of two decades. The three countries were the Ivory Coast, Ghana, and Zambia. The prospectus for this conference noted that world grain production doubled in the last three decades. The doubling PNAS is available online at www.pnas.org. of grain production in three decades was a remarkable achievement, without parallel in the history of the world. Such an important accomplishment would seem to merit at least a mild amount of applause. But the next few sentences of the prospectus seem to imply that the doubling has left the world with a great array of problems that will be difficult, if not impossible, to solve. Concern over the impact of popu- lation and the spread of agriculture and other forms of human settlements on the environment and the capacity of the world to provide for a growing population is hardly new. This statement is supported by the words of Quintus Septi- mus Florens Tertullianus, written about A.D. 200: "Indeed it is certain, it is clear to see, that the earth itself is more cultivated and developed than in early times . . . The most charming farms obliterate empty spaces, ploughed fields vanquish forests, sandy places are planted with crops, stones are fixed, swamps are drained, and there are great cities where formerly hardly a hut ... everywhere there is a dwelling, everywhere a multitude, everywhere a government, everywhere there is life. The greatest evidence of the large number of people: we are burdensome to the world, the resources are scarcely adequate to us and our needs straiten us and complaints are everywhere while already nature does not sustain us. Truly, pestilence and hunger and war and flood must be considered as a remedy for nations, like a pruning back of the human race becoming excessive in numbers." "translated from Latin by Bart K. Holland (3~. Whether or not the world is faced with rapid population growth, we do know that the rate of world population growth is now much lower than it was and that prospective rates of population growth are expected to be much less than either recent or current rates. From 1950 to 1990, the annual rate of growth of world population was 1.88%; the annual rate of growth peaked in 1965-1970 at 2.1%. Bos et al. (4) of the World Bank projected that the annual rate of growth of world population for 1995-2000 would be 1.43% and for 2000-2005, 1.24~o, and for 2020-2025, 0.85~o a decline of 60% from the peak rate. Is 1.43% or 1.24% annually a rapid rate of population growth? What about the 1.04% projected for 2015-2020? The rates are not holding constant. They are projected to decline and decline substantially over the next quarter century. At least to me, these are substantial declines and do not represent a rapid growth rate unless any positive rate of growth is so considered. It is quite common to note with alarm that one or more measures of world per capita production or consumption is declining. Let me state categorically: in the world of the past half century, changes in world per capita production or consumption provide little or no useful information. It is possible for world per capita production or consumption of grain to remain constant or to actually decline a little, and *To whom reprint requests should be addressed. e-mail: dgjohnson@ uchicago.edu. 5915

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5916 Colloquium Paper: Johnson yet for every person in the world to be consuming more grain. How can this be? The reason is that there are large differ- ences in per capita food consumption by income levels, and the population weights used to calculate the world per capita averages over time are shifting weights the low-income consumers with their lower per capita consumption of grain have increased in relative importance in the world's popu- lation. Although the example given is possible, it is only hypothetical. But we do know that from 1979-1981 to 1990-1992 that world per capita grain production increased only from 325 kilograms to 326 kilograms while per capita production in developing countries increased by 7% (14 kilograms) and in developed countries by To (14 kilograms) (51.! Concern is expressed that world agricultural output will not grow at as rapid a rate in the future as it did, say, between 1960 and 1990. It is argued that world grain production and world food production as well have grown quite slowly during the l990s and that world per capita grain production has declined. World grain production has not kept pace with world population growth since 1984. Is this a cause for alarm? As I will argue, it is not. The Rate of Output Growth Is Slowing. Let me state at the outset that the future growth of world grain production and of any other measure of world food supply will be signifi- cantly slower than the annual rate of growth during 1960- 1990. This is nearly as certain as it is that the sun will rise tomorrow morning. And it is not a cause for alarm or concern and don't let any one tell you that it is. Or at least don't believe them if they do. The reason for the slower growth will be economic rather than the limitations of the biological potential for increasing yields or deterioration in the natural resources used in producing food. Farmers of the world would face disaster if future output grew at the same rate as in the past several decades because if output grew exogenously at that rate, there would be sharply declining real prices. Consequently, output will not grow at the same rate as in the past. But let me hasten to add that the supply of food will grow more rapidly than will demand, real food prices will fall, and per capita food consumption in developing countries will con- tinue to grow at about the same rate as in the past two decades. It will be the growth of demand that will limit the growth of agricultural output over the next quarter century. This is no change from the experience of the last three or four decades of the 20th century. The primary difference is that both demand and output will grow at much slower rates than in the recent past. While grain output increased by nearly 2.5~o annually from 1960 to l99O, it did so while the real international prices of grain fell by about 40% (see Table 1~. The growth of grain output would have been substantially greater had real grain prices not declined by such a large percentage. In other words, if demand had grown faster so that real grain prices would not have declined, the growth of supply would have been greater than it actually was. There would have been incentives for farmers to produce more by bringing more land under cultivation, increasing the appli- cation of chemical inputs per unit of land cultivated, and taking other measures to increase yields that would have been profitable at substantially higher real output prices than they actually received. There would also have been incentives for both governments and the private sector to have invested lThe same difficulty in interpreting an average applies among regions in developing countries or even between rural and urban areas in a given country. Whenever there are differences in consumption levels that are correlated with changes in the rates of growth of population, changes in per capita averages will transmit little information and may, in fact, be misleading. Proc. Natl. Acad. Sci. USA 96 (1999) Table 1. Real export prices for wheat, maize, and rice in selected years from 1910 to 1997 Year(s) Wheat Maize Rice 1910-1914 1925-1929 1930-1934 1935-1939 1945-1949 1950-1954 1955-1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 299.3 308.3 236.4 236.4 385.1 284.3 206.5 194.5 206.5 209.5 206.5 206.5 185.6 185.6 191.6 179.6 170.6 158.6 161.6 161.6 239.4 329.2 284.3 239.4 173.6 182.6 200.5 197.5 185.6 167.6 158.6 149.7 140.7 119.7 95.8 113.7 143.7 120.1 91.4 112.7 110.0 110.3 134.9 157.2 127.7 221.5 227.5 254.4 254.4 281.3 239.4 182.6 158.6 155.6 155.6 167.6 170.6 170.6 167.6 161.6 143.7 143.7 155.6 149.7 137.7 188.6 236.4 227.5 191.6 155.6 149.7 149.7 149.7 149.7 116.7 131.7 137.7 113.7 95.8 74.8 101.8 104.8 99.7 95.1 93.4 88.9 91.7 97.5 122.2 97.6 366.3* 484.6t 394.3 421.1 390.2 338.6 369.4 777.8 1,013.1 621.5 417.4 419.1 526.5 424.4 483.3 492.4 293.0 273.4 244.7 209.7 212.1 225.5 281.7 285.8 249.7 273.4 249.9 239.3 280.0 262.7 278.9 279.2 All prices are in 1982 dollars per ton deflated by the U.S. wholesale price index. Wheat and maize prices are U.S. export prices, and rice price is Thailand milled rice, 5% broken. *1950. tl955. substantially more in agricultural research and thus have increased output-enhancing innovations and contributed to a higher rate of growth of agricultural output. But the fact was that the growth rate of supply exceeded that of demand for 1960-1990 and real farm prices fell, not by a little but by a lot. The growth rate of demand is not the same as the growth rate of consumption or use. The growth rate of demand measures the shift in the demand function and it would be the same as the growth rate of consumption only if real prices remain unchanged. Put another way, the growth rate of consumption is the result of the shift in the demand function and the change in real prices. From 1960 to l99O, the world's demand for food grew more slowly than did supply. This is the reason that real international prices of grain declined so very much in the three decades. Had

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Colloquium Paper: Johnson demand increased at the same rate as supply, real food prices would have remained constant. As I shall show later, the growth of demand for grain (and food generally) will be at a much lower rate than in the recent past. To approximately match the growth of demand, the growth of supply will be much lower than in the past. Recent Trends in World Grain Production. It has been noted that since 1990 or even earlier world per capita grain production has been declining, and some believe that this is a cause for concern. There are two good reasons why this decline, which has occurred, should not be a matter of significant concern to the populations of the developing countries. As noted earlier, changes in world per capita measures of production or consumption need to be interpreted with extreme caution; per capita grain production tells us almost nothing about the adequacy of food supplies for particular large segments of the world's population.! As noted, world per capita production of grain was 325 kilograms in 1979-1981 and 326 kilograms in 1990-1992. If per capita production had remained constant in both the developing and developed regions between 1979-1981 and 1990-1992, world per capita production would have declined from 325 kilograms to 312 kilograms a decline of 4%. When there are divergent regional trends in population growth, world average figures are not reliable measures of what is happening to the production or consumption levels in either the developing or developed countries. The other reason is that the decline in per capita world grain production that has occurred in the l990s needs careful interpretation concerning its cause and its implications to the large majority of the world's population the population of the developing countries. The decline in the rate of growth of world grain production in the l990s is due primarily to the sharp decline in grain production in Central and Eastern Europe (CEE) during the transition from planned econo- mies to market economies. If grain production in that region had been maintained at the 1985-1989 level rather than declining by more than 100 million tons, the rate of growth of world grain production from 1990 to 1996 would have been at an annual rate of 1.8%, only a little below the rate of 2.1~ for the 1980s (74. Did this decline in grain production in the CEEs adversely affect consumption in the rest of the world? The net effect of the transition process on both production and consump- tion of grain in the CEEs was to increase grain supplies in the rest of the world compared with what it would have been if grain production, utilization, and trade had been maintained at the 1985-1989 levels. This outcome occurred because the consumption of grain in the CEEs decreased more than did production. This was due mainly to two factors. First, the consumption of livestock products was highly subsidized in the U.S.S.R. as well as elsewhere in the region. Consumers in the U.S.S.R. paid less than half of the cost of bringing meat and milk to the grocery store. These subsidies were elimi- nated after 1991, and the consumption of livestock products was reduced substantially as a result. In addition, real per capita incomes have fallen, reducing the demand for live lThe per capita grain consumption in the developing countries has increased at a somewhat higher rate than production because net imports have increased at a faster rate than population. Whereas the developing countries were net importers in both 1980 and 1990, the percent increase in net imports was only moderately greater than the percent increase in population. Net grain imports per capita in 1980 were 18 kilograms and in 1990, 21 kilograms. If net grain imports of developing countries increase to 160 million to 210 million tons as projected in the three studies referred to earlier per capita grain imports would increase to 28-36 kilograms per capita by 2010 (6~. To put this amount in perspective, imports would account for about 12-15% of grain use in the developing countries in 2010. Proc. Natl. Acad. Sci. USA 96 (1999J 5917 stock products and, thus, the use of grain as feed. The net effect has been that annual grain imports by the CEEs have fallen by at least 30 million tons, compared with the late 1980s. Consequently, the rest of the world has been able to increase its utilization of grain by 30 million tons as a result of the changes that have occurred in the CEEs. Again let me emphasize, one must exercise great care in interpreting average changes for the world, such as declining average yields or declining per capita production or consumption. It behooves us to look behind the changes in the world averages and determine what factors were involved before coming to any conclusion concerning the interpretation of the change in the average. Growth of Demand. Demand growth for the next two decades will be at a much lower rate than in the recent past. The growth in the world's consumption of food is a function of four variables population, real per capita income, the relative price of food, and differential rates of population growth among countries or regions with different levels of real per capita incomes. Real incomes affect food demand through the income elasticity of demand a 1% increase in real per capita income increases per capita demand by much less than 1% in the case of grain perhaps by about 0.10- 0.25%., As real incomes increase around the world, the income elasticity of demand declines. Food prices at the farm level have a minor effect on per capita food consumption because the farm price represents only a part of the cost to urban consumers, and the price elasticity of demand has become quite low and will be lower in the future than it now is. The primary factor affecting the growth in demand for food is population growth. There seems to be little recognition by those who express concern about future food demand growth of how fast fertility is declining in today's world and how much further it will decline in the years ahead. Based on data for 1960- 1990, the growth of population accounted for approximately three fourths of the growth in total grain consumption. Increased real per capita incomes and declining grain prices accounted for the remaining quarter of the increase in per capita consumption. Of the 2.46% annual growth in total grain consumption, population growth accounted for 1.9% and per capita consumption growth for 0.55%. What does the future hold? The projections of world population growth by the United Nations and the World Bank imply a sharp fall in prospective growth rates compared with those for the last decades of this century. The projections that I shall refer to are the medium projections, not the high or the low. Two recent projections of the world population for 2020 are 7.67 billion by the United Nations and 7.742 billion by the World Bank. These represent percent increases relative to 1990 of 45.6 and 47.0 respectively. These compare with the actual growth of world population of 77% from 1960 to It is not implied that the 30 million tons annually has gone to importers; some part of it remained in the exporting countries. The only point is that the decline in grain production in the former U.S.S.R. has not imposed a reduction in grain utilization in the rest of the world. TThese are rough estimates of the income elasticity of demand, with 0.25 being for the developing countries. An annual growth of real per capita income of 2% would result in annual increases in the per capita consumption of grain of 0.5%. Because of the uncertainties concern- ing developments in grain production and incomes in the former Soviet Union it is much more difficult to estimate the income elasticity of demand for grain in the developed countries. Pinstrup- Andersen et al. (8) projected a very small increase in world per capita demand for grain from 1993 to 2020 less than 2% for the entire period, but with a significant increase in the per capita consumption of grain in the developing countries.

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5918 Colloquium Paper: Johnson 1990.ll According to the World Bank estimates (4), the growth rate of population is projected to decline by 38%, from an annual rate of growth of 1.9% for 1960-1990 to 1.3% for 1990-2020. In 1994, the three major international orga- nizations with concerns for agriculture, the Food and Agri- cultural Organization (FAO), the International Food Policy Research Institute (IFPRI), and the World Bank (WB), completed studies of the prospective food demand and supply to 2010. There was remarkable unanimity of results, both with respect to the growth of demand and to supply. The consensus of the three studies was that for the two decades ending in 2010, world per capita consumption of grain would remain approximately constant, but would increase in both developing and developed countries by small percentages (9~. According to these studies, the world consumption of grain is and will be moved almost entirely by population growth. At the time the studies were being prepared, the projection of the annual rate of world population growth for 1990-2010 was 1.5 To. Their consensus estimate was that world consumption of grain would grow at approximately 1.5-1.7~o annually, which was consistent with their conclusion that the weighted average of world per capita consumption would increase very little. Extending the consensus projection of the three studies for 1990-2010 to the year 2020, I project that the production of grain will increase by 17% in the developing countries in 2020 and by 9% in the developed countries. This would increase per capita production to 250 kilograms in developing countries and to 750 kilograms in the developed countries. In 2020, it is projected that the developing countries will have 82.2% of the world's population, up from 77~o in 1990. World per capita production in 2020 would be 339 kilograms t(0.178 x 750) + (0.822 x 250) = 3393.~* This is an increase of To from the 1990 world per capita production. In terms of annual growth, the projected growth in world utilization of grain would be very slightly more than 1.3% annually the projected rate of growth of population plus a 4% increase in per capita use. Enough Food to Eliminate Malnutrition? There are many people in the world who are chronically undernourished. As of 1988-1990, 781 million were estimated to be chronically undernourished. The indicated projection of demand assumes that the number will decline to 637 million in 2010 and to about 575 million in 2020. The primary factor responsible for mal- nutrition is low income levels rather than an inadequate supply of food. Low levels of caloric intake are not the sole cause of malnutrition and perhaps not even the major cause. Deficien The medium projections may well be on the high side for years some distance in the future. The reason is that in the two projections noted in the text, the demographers who make the projections must decide what to assume for the countries that now have fertility rates below replacement level. They resolved this issue by assuming that fertility will actually increase to the replacement level in the not too distant future. For example, Germany is assumed to increase its fertility level to 2.1 (actually 2.076) by 2035 compared with its recent level of 1.3 (4~. China is thought to have a fertility rate of 1.9 in 1995-2000 and this is projected to increase to 2.127 in 2025-2030. I report this aspect of the two projections to make it clear that the projected levels of population do not assume that countries that have fertility below replacement levels will continue to follow the path of recent trends. Quite the contrary, it is assumed that in these countries fertility will increase over the next three decades or so and in some cases by significant percentages. So far as I know, there is no foundation for this assumption but some assumption had to be made to complete the projections. * *Per capita utilization of grain would differ somewhat from per capita production because of projected imports of grain by the developing countries. In 1990, developing countries imported 21.5 kilograms of grain per capita and they are projected to import 28-36 kilograms in 2010. If developing country imports continue to grow between 2010 and 2020 at approximately the same rate as from 1990 to 2010 then per capita consumption might be 285-290 kilograms. Given the shift in population weights, the increase in world per capita utili- zation would be a little less than Who. Proc. Natl. Acad. Sci. USA 96 (1999J cies in the availability of micronutrients such as vitamins A and D, iron, iodine, and calcium, plus the heavy incidence of dysentery in many low income areas of the world, contribute to the problem. The Food and Agricultural Organization (10) has estimated that to increase the dietary energy supply to 2,300 kcal (1 kcal = 4.18 J) per day in 2010 of the countries that had a supply of less than 1,850 kcal/day in 1990 would require 46 million tons of grain. This assumes that grain supplies 60% of the energy supply and would do so in 2010. The addition to the supply of grain for the developing countries that in 1990 had per capita daily energy supplies of less than 1,850 kcal/day would be 8.5% of the projected supply in 2010, but only 2.4% of projected world grain production. It would require a rather modest increase in the price of grain (almost certainly no more than 10%) to achieve such an increase in world grain production. But even if all of the increase in calories had to come from grain, the required increase in grain would be about 75 million tons, or less than 4% of current world grain production, and approximately 2.5% of projected world production in 2020. Recent Price Trends. Table 1 gives data on the real prices of wheat, rice, and corn for the period since 1950. These are based on U.S. export prices for wheat and corn and Thailand's export prices for rice, and the deflator is the U.S. wholesale price index. During the 1990s, the international prices of grain have been nearly the lowest that they have been in the 20th century. This is in spite of the temporary run-up in prices in the mid-199Os. The price increases in 1995 and 1996 have now been largely erased, and the real export prices in 1997 had almost returned to the low levels of 1990-1994. This year, China introduced a price support program to raise the low market prices of grain that farmers were receiving. China is not now a significant importer of grain, in spite of wild and unsupported projections that it would be. China did import significant amounts of grain nearly 20 million tons in 1995 but this was done in error; China had a bumper grain crop in 1995 as it did in 1996 and had no need for imports. China now faces the problem of large stocks and low domestic prices of grain. It exported an average of 5 million tons of grain in 1992, 1993, and 1994 (11), in contrast to its position as a net importer of 13 million tons a decade earlier (1980-1983) (12~. President Clinton visited China, and not long after return- ing, he also announced that the price of wheat was too low. He authorized the purchase by the U.S government of 80 million bushels of wheat, which will be used for food aid and thus (largely) removed from the domestic and world market. It is estimated that this action will increase the market price of wheat by 10 to 13 cents per bushel. It is quite remarkable that politicians in the world's two largest grain-producing countries should simultaneously decide that so much grain had been produced that it was necessary to take action to increase grain prices. True, a factor in the current low prices of grain is the economic slowdown in several Asian countries combined with a delayed output response by farmers to the relatively high real prices of 1995 and 1996. However, the current international market prices of grain are not significantly below those that prevailed in 1990-1994. Not all of the implications of the current low grain prices are positive. The low prices do not encourage governments to take tTI have used the U.S. wholesale price index rather than the World Bank's index of the prices of manufactured products exported by the industrial countries to the developing countries. Over time that index increases much more than the U.S. wholesale price index and if it is used as a deflator, the declines in the real prices of grains are much greater than what is reflected in Table 1. For example, if the World Bank's index is used, the real international price of corn declined by 48~o between 1950 and 1990. In Table 1, the decline is Who. The U.S. wholesale price index has a much broader commodity coverage than the World Bank index. The U.S. index includes oil and coal, for example.

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Colloquium Paper: Johnson the long-term view with respect to investment in agricultural research or changing policies that adversely affect farm output. It is possible that if these low prices continue for another year or two, as they might well do, world grain production will stop expanding and grain stocks will decline, resulting in another price spike such as occurred in 1995 and 1996. This will not presage a significant decline in the long run growth of grain output, but price instability imposes costs on both farmers and consumers. Will Cropland Area Increase? It may be noted that in the studies of future food supplies that I have used, there is an implicit assumption that the area devoted to grain will increase little, if at all, in the years ahead. True, there has been little increase in recent years. In fact, the grain area harvested in 1996 was the same as in 1970 (7~. But why should there have been an increase in harvested area? It was cheaper to find substitutes for land than it was to increase the area of land devoted to grain. With the rapid rate of decline of the real price of grain, there was little incentive to pay the substantial cost of increasing the cropland area even though there is widespread agreement, even including the Club of Rome, that the amount of arable land in the world could be increased by 50~o (13~. I think it is unlikely that over the next two decades there will be any significant increase in the cropland area, but there could be if agricultural prices increased significantly. But higher real prices for farm products are highly unlikely, so it is unlikely that we will see the development of much new cropland. A failure to increase cropland will be a signal that yield increases on existing cropland have been sufficient to meet the slow growth in demand that will occur. Two Possible Threats to Future Food Supply. The increase in irrigated area since 1950 has been an important factor in the higher yields of grain and other agricultural products. It is argued that it is unlikely that there will be a significant increase in irrigated area in the near future and that it is possible that the irrigated area could decline because of depletion of existing supplies of stored water, of larger withdrawals from aquifers than the rate of replacement, or of increased use of limited water supplies by nonagricultural activities. These outcomes cannot be ruled out. No country in the world properly manages its water supply. Almost everywhere, water is a common-property resource and no value is attached to the water at the source, whether from an aquifer or from a storage facility such as a lake or a reservoir (14~. At most, farmers are charged for the cost of delivering the water to the field. Several countries actually subsidize the delivery of water to urban consumers and for irrigation. A large percentage of the existing irrigated water is wasted, and there is a substantial potential for saving water with little effect on output; the way water is generally priced, the individual farmer has little incentive to economize in its use. A common practice is to provide a farmer with a particular volume of water at a fixed price. The farmer gains nothing by using less than the fixed volume of water. Or if water is being pumped from an aquifer, there is seldom a limit to the amount of water that can be withdrawn, and there is no charge for the value of the water in the aquifer. Often, as is true in India, the electricity used to pump the water is heavily subsidized: in the Punjab, the electricity used in pumping water for irrigation is free. Until governments recognize that water is a valuable resource and price it properly, there is reason to be concerned that the savings in irrigation water will not come soon enough to prevent some irrigated areas from being abandoned because they have exhausted their available supply of water or they have been forced to give up their water for a higher value use. Irrigated areas may also be lost to salinization and waterlog- ging, but at a cost these can be corrected. Another common property resource that is important to the world's food supply is that of ocean fisheries. Here the misuse of the world's resource is similar to that for irrigation water. Proc. Natl. Acad. Sci. USA 96 (1999) 5919 Outside the 200-mile limit, there is no significant effort to limit the amount of fish taken access to the commons is not limited. The amount now being taken exceeds current annual growth, and the breeding stocks of several important fish species are in serious danger of depletion. One important reason for the depletion of ocean fisheries has been the technological changes in the methods of catching fish that have occurred in the past three or four decades. Another reason is that many governments subsidize their fishing industry. Water and ocean fishing are two areas where major prob- lems affecting the world's food supply either exist or poten- tially may do so. In both cases it takes action by governments to find appropriate solutions. Although markets could be part or all of the solution, markets for common-property resources cannot exist without governments creating the necessary framework by assigning property rights or by using markets to privatize the rights. In one way or another, governments must find ways of restricting access to common-property resources. In the case of water, each government is largely in control of its own destiny, although there are numerous examples of where a common water source is shared among two or more countries. In the case of ocean fisheries, agreement is required among many governments if the world's fisheries are not to be seriously depleted. If governments are either unable or un- willing to find solutions for the common property problem that falls entirely in their own jurisdiction, it may be unrealistic to assume that they can find solutions for a common property problem that requires agreement among scores of govern- ments until the catch from ocean fisheries is substantially lower than the current level and fish prices are much higher than they are now. Unfortunately, fish farming has offset the loss of catch from the oceans and thus permits governments to delay seriously tackling the issue. I say it is unfortunate because there is no feed cost to fish taken from the ocean; the only cost is catching them. But most farm-raised fish require feed and in significant amounts. By not solving the ocean fishing problem, a source of food that directly competes with neither humans nor domestic animals is lost. Has the World's Cropland Been Seriously Degraded? It is alleged that the quality of the world's land resource has been degraded through erosion, loss of organic matter, and other forms of loss of potential productive power. There are claims that enormous quantities of topsoil are lost each year to water and wind erosion. Does the world enter the next millennium with soil that is badly degraded and of lower productive capacity than it was when we entered the 20th century or in 1950 when the recent surge in agricultural productivity started? There are many allegations that this is the case. Such allegations emanate from the Worldwatch Institute and the World Resources Institute, for example. Some aspects of these claims were endorsed by the presidents of the Chinese and the United States academies of sciences in a statement issued in Beijing on January 16, 1997. They agreed that "The need for improvement is urgent, since all resource indicators- changes in the atmosphere, loss of topsoil, loss of forests, the extinction of organisms have moved sharply and continu- ously downward during the second half of the 20th century, while both world population and levels of consumption con- tinue to rise. Globally, these trends are not sustainable over the long run." Among the impending disasters, I shall consider only the loss of topsoil from agricultural lands. ttErosion occurred long before man was a factor in affecting the world's environment. And not all erosion has adverse effects on the productivity of the land. An example is the southwestern part of the state of my birth, Iowa. This part of Iowa has some of the deepest topsoil in the world, and much of it was created by erosion; it was transported by wind from Texas and Oklahoma. The soil is much more productive where it now is than if the erosion had not occurred.

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5920 Colloquium Paper: Johnson I agree with Peter H. Lindert (15, 16) of the University of California at Davis that the claims that there have been serious loss of topsoil from agricultural lands or other forms of widespread deterioration of the productive capacity of farm land are without foundation, i.e., not based on evidence of change over time. Lindert (16) states the following: "Lacking an actual quantitative history of soil conditions beyond exper- imental plots, scholars have fixed on the useful but risky task summarized by the title of this section. The literature has three main shortcomings: (1) using crude indicators that prove little about human impacts on the soils, (2) using trends in cultivated land area as clues about land quality, and (3) using single-snapshot predictions as if they were time-series data.''1TlT Lindert used long-run data from two large developing countries, China and Indonesia, in an effort to measure changes in the quality of the land resource. The data he used were soil surveys, dating from the 1930s to the relatively recent past, the 1980s in China and 1990 in Indonesia. This is not the place to provide a detailed summary of his results, but his following brief summary will provide a sharply different perspective than those that are commonly given (16~. "The broadest outlines of the interaction of soil and agri- culture are now somewhat clearer for two developing coun- tries. We have some idea which dimensions of soil quality have improved and which have not. Soil organic matter and nitrogen appear to have declined on cultivated lands in both China and Indonesia. Total phosphorous and potassium have generally risen. Alkalinity and acidity have fluctuated, with no over overall worsening. The topsoil layer has not gotten thinner. "Some of the mixed trends revealed here have more effects on yields than others. China's patterns show that the decline in soil organic matter and nitrogen makes little difference, pre- sumably because fertilizers can substitute for the soil endow- ment. More relevant are the pH and total potassium, for which the trends are better." Based on comparisons of soil surveys over a period of 50 years, Lindert (16) reaches the remarkable conclusion for China and Indonesia: "The topsoil layer has not gotten thin- ner." This conclusion is wholly inconsistent with the state- ments from the presidents of the two academies of science and from most other commentators on the subject. This is not to deny that erosion exists in China, after all, the Yellow River didn't get its name by accident. But to note that there are obvious signs of erosion does not tell us from whence it came or why it occurred. The data assembled by Lindert indicates that it has not come to any considerable extent from farmland. I find it hard to believe that farmers are as careless with a resource that is very important to them as is implied by much of the opinion expressed concerning the alleged enor- mous loss of topsoil. I have long held that farmers are at least as smart as the rest of us and I believe that they know how to act in their own interest. It is not in the interest of farmers to The title of the section was "Judging Soil Quality Trends Without Measuring Them?" tLindert (14) adds the following: "Most importantly, the proffered data on soil quality trends are neither data nor trends. Rather they are experts' predictions from a single snapshot, derived by combin- ing data on slope, climate, and land use with what happens to such soils under experimental conditions. Sometimes it is refined into "expert opinion," as in the GLASOD map, but it is still not based on any observation before the mid-1980s. That it is not a real history does matter, since the complexity of human soil interventions over a large countryside can defy simula- tion on experimental plots. Farm populations react to the soil itself with complex mixtures of crop rotations, amendments, fertilizer application, investments in water control, and sometimes neglect and mismanagement. To know the soil impact of recent human inter- ventions, we need data on actual practice over long time spans and large areas." Proc. Natl. Acad. Sci. USA 96 (1999) prevent all erosion because there are likely to be costs involved. But in the range where the benefits and costs of preventing erosion are approximately equal or the benefits exceed the costs, it seems reasonable to assume that farmers are acting in their own interest, at least until there is solid evidence to the contrary. Lindert's analysis of historical data for two important countries indicate that there may not be evidence to the contrary. Soil surveys do exist in other countries. It is perhaps time that more use is made of this neglected source of information about the state of the world's land resource and less reliance is placed on information that lacks a time dimen- s~on. Concluding Comments. The people of the world are better fed than ever before. And more people will have more adequate nutrition 20 years from now if the governments of the world carry out their responsibilities with the same care and intelligence as farmers display in their production activities. In my opinion, an important danger to the future of the adequacy of the world's food supply are low international prices, given the responses governments of both developed and developing countries are likely to make. In the face of current low international prices for grain, will governments maintain their investment in agricultural research? The declining real support for agricultural research in the past decade or so has been to some degree a response to low prices. If there are to be continuing improvements in the adequacy of food supplies in developing countries, the support of agricultural research must not be reduced and probably should be increased. A second danger is that there are still developing countries that are following policies that discriminate against agriculture and farm people. As long as these policies persist, the growth of food production will lag and people will unnecessarily suffer from malnutrition. A large percentage of the malnourished people in the developing countries live in rural areas and depend on agriculture for all or most of their incomes. For these people there is a close link between farm prices, food output growth, incomes, and their nutritional status. Financial assistance from the William ImMasche Foundation is gratefully acknowledged. 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