Most future increases in global demand for food are expected to arise by 2050. By that time, demand could increase by 2.5 to 3.0 times the present level. The global agricultural system will fail to increase food production that much over the next 60 years if policies to achieve agricultural sustainability focus primarily on increasing the supplies of energy, land, water, climate, and genetic resources in the present state of knowledge. The potential supplies of these resources simply are inadequate. The only hope of sustainably meeting the future increase in demand for food is to invest in expanding the supply of knowledge about agricultural production.
Concern about the world's ability to feed itself dates at least from the time of the English economist Thomas Robert Malthus in the early nineteenth century. The concern has waxed and waned since then, but the adequacy of global agricultural capacity still figures prominently on the policy agendas of many countries and international organizations concerned about economic development. It surely will be prominent in the forthcoming deliberations of the United Nations Conference on Environment and Development.
A sustainable agricultural system is one that can indefinitely meet demands for food and fiber at socially acceptable economic and environmental costs. There is unavoidable ambiguity in the meaning of socially acceptable costs. No consensus has emerged about what standards should be used to judge acceptability. Yet concern about costs drives the current discussion about sustainability in agriculture and development generally. If we are to think fruitfully about the concept of sustainability in agriculture we cannot avoid thinking about costs.
Concern about sustainability reflects a sense of intergenerational obligation. With respect to agriculture, this means that each generation is obliged to manage its affairs so as to provide subsequent generations with the opportunity to engage in agricultural production at acceptable economic and environmental costs.
Sustainability cannot be discussed usefully without specifying the spatial scale of production units and the possibilities for movement of goods and people among units. In the absence of such possibilities, the agricultural system of a region may be unsustainable because it cannot meet the demands on it at costs the people of the region find acceptable. Where trade and emigration are possible, the relevant spatial scale is greater, a region can substitute lower-cost food and fiber for its own high-cost production, and people can move from one region to other regions where costs are lower. Thus the agricultural system for a group of regions (or countries) linked by trade and migration of people may be quite sustainable even though the systems for each separate region (or country), without the linkages, would be unsustainable. Most farmers are connected through trade to markets for their output in their immediate region and often to more distant regional, national, and international markets. Thus the spatial scale appropriate for discussions of sustainable agriculture is global.
Intergenerational obligation, spatial scale of production units and movement of goods and people among units, and scale of demands for production create a workable meaning of sustainable agriculture.
A discussion of sustainable agriculture must also specify the scale of the demands for production imposed on the system; in general, the problems of achieving sustainability become more difficult as demand for the system's output increases. The quantitative dimension of sustainability thus is crucially important.
Taken together, the above concepts create a workable meaning of sustainable agriculture. That meaning has a temporal dimension—the indefinite future; a spatial dimension—the world as a whole; a quantitative dimension—the demands placed on the system now and in the future; and a normative dimension—the need to meet those demands over time at economic and environmental costs that society deems to be acceptable. In considering the sustainability of the present agricultural system in these respects, it is useful to begin with prospective future demands on the system.
The global demand scenario
If current population projections by the United Nations are accurate, most of the future increase in global demand for food will occur by about 2050. By then global population will be close to the expected ultimate total of 10 billion to 12 billion (the present global population is 5.2 billion). In addition, if the global system as a whole proves to be sustainable, per capita income in the less developed countries (LDCs) will have risen to the point at which additional income would stimulate little additional spending on food because at that income level most people would be adequately nourished. In more developed countries (MDCs), per capita income already is at that point. Thus the critical period for the global agricultural system is roughly the next 60 years. If the system can sustainably meet the increase in demand over that period, it probably will be indefinitely sustainable.
Research at Resources for the Future (RFF) indicates that the projected increase in global population, combined with a plausible increase in per capita income in the LDCs, could increase global food demand 2.5 to 3.0 times the present level by the middle of the next century. The sustainability question is whether the global agricultural system will be able to increase food production that much over that period at acceptable costs. The answer to the question will depend on the ability of the system to mobilize the resources—the social capital—necessary to sustain the production increase.
The concept of social capital
The question of sustainability can be put in terms of the kinds and amounts of social capital that intergenerational equity requires to be passed from one generation to the next. Social capital consists of all the natural and human-made resources used to produce goods and services valued by people. For agricultural sustainability, social capital includes supplies of energy, land, irrigation water, plant genetic material, climate, and knowledge embedded in people, technology, and institutions.
Energy. Over the next several decades global energy supplies are likely to be increasingly constrained by both rising real prices and concerns about the environmental costs of fossil fuels—among them the costs of the greenhouse effect on the global climate. Experience since the run-up in energy prices in the 1970s suggests that farmers should be able to adjust reasonably well to future increases in energy costs, should they occur. There is little doubt, however, that eventually the costs of fossil fuels will rise high enough to pose a threat to sustainability, not only in agriculture but also in the economy as a whole. Avoidance of the threat will require development of renewable and other nonfossil sources of energy. When this must occur is uncertain; but that in time it must occur is not.
Land. The supply of land has both quantitative and qualitative dimensions. The United Nations Food and Agriculture Organization estimates that worldwide some 1.5 billion hectares currently are in crops of all kinds. Sketchy estimates indicate some 1.8 billion additional hectares have the soil and climate conditions suitable for crop production. However, for several reasons this estimate surely overstates the amount of land that could be converted to crop production over coming decades at acceptable economic and environmental costs. Much of the potential cropland is of inferior quality in comparison with current cropland. Moreover, most of it is in Africa and Latin America, but much of the future increase in demand for food will be in already land-scarce Asia. Asian countries will be able to draw on imports to offset some of their land constraints, but concern about food self-sufficiency probably would limit this response. Asian countries are not likely to view a hectare of potential land in Africa and Latin America as equivalent to a hectare within their own borders.
Estimates of potential cropland are also overstated because they do not take account of the opportunity costs of converting the land to agriculture. Yet these costs could be significant. Much land around urban areas in LDCs will be priced out of the agricultural market by demands to accommodate rising urban populations. And the clearing of forests in order to graze animals and raise crops already is seen by many as having high opportunity costs because of the losses of plant and animal genetic diversity that clearing is believed to entail. Governments in the tropics are under increasing pressure from governments of MDCs and the international environmental community to reduce these losses by curbing forest clearing, and the pressure likely will continue to grow.
Estimates of potential cropland overstate the amount of land that could be converted to crop production at acceptable economic and environmental costs.
As noted, the average quality of most potential cropland is less than that of land presently in crops. In addition, the quality of agricultural land can be and is degraded by soil erosion, salinity buildup in irrigated areas, compaction from overuse of heavy tractors or trampling by animals, loss of nutrient supply through overgrazing, and other kinds of damage. Global land degradation through these various processes is widely believed to be severe. However, work done at the World Bank and elsewhere indicates that the evidence of land degradation is too sparse to warrant firm conclusions about the extent of the problem. Research at RFF and at the U.S. Department of Agriculture indicates that soil erosion in the United States, widely believed to be a major threat to the sustainability of the nation's agriculture, is not in fact a serious problem. Comparable studies have not been conducted for other countries. It is worth noting, however, that global crop yields (output per hectare) continue to increase, as they have for the last 40 years, indicating that on a global scale soil erosion has not so far seriously impaired land quality.
Estimates of the potential for additional irrigation must take account of the environmental and economic costs of irrigation projects
Water. About 17 percent of the world's cropland, producing about one-third of global crop output, is irrigated. Almost 75 percent of this land is in the less developed countries, 62 percent of it in Asia—mostly in India, China, and Pakistan. Africa has a little more than 4 percent of the global total of irrigated agricultural land, and Latin America about 6 percent.
World Bank estimates indicate that, based solely on soil and climate factors, the present area of irrigated land world-wide could be increased about 50 percent. However, these estimates, like those for potential cropland, almost surely over-state the real potential for additional irrigation. The estimates give too little weight to the economic and environmental costs of additional irrigation. World Bank studies of India's experience show that the real economic costs of recent irrigation projects were substantially higher than the costs of earlier ones, in large part because the best sites were developed first. Nor do the estimates of potential irrigation take proper account of sharply rising demands for nonagricultural uses of water in urban areas and for instream flows to protect aquatic habitat.
Estimates of the potential for expanding irrigation at socially acceptable costs do not properly account for the rising demand for nonagricultural uses of water and inefficiencies in the use of irrigation water.
Much irrigation water is inefficiently used, not only because it is typically priced well below its true social value but also because much of it is managed by large, unwieldy public bureaucracies. Even if these inefficiencies were removed—a formidable undertaking—the potential for expanding global irrigation at socially acceptable economic and environmental costs surely is well below that suggested by the World Bank estimates.
Climate. Although there now is a strong scientific consensus that the global climate will change over the next 50 to 100 years because of the greenhouse effect, there is no consensus about the consequences of this for global agricultural capacity. Studies conducted for the Intergovernmental Panel on Climate Change and by the U.S. Department of Agriculture suggest that climate change might reduce global agricultural capacity by 15 to 25 percent. However, these estimates make no allowance for the ability of farmers to adjust to the changed climate or for agricultural research institutions to develop new technologies better adapted to the changed climate. Research at RFF on the impacts of climate change on agriculture in the midwestern United States indicates that these various adjustment processes could virtually eliminate the negative effects of a hotter and drier climate in the Midwest.
Steps taken to limit climate change would reduce the damage to the social capital represented by the climate. In the best of circumstances, however, the climate will contribute little if anything to meeting the prospective increase in global demand for food and fiber.
Genetic materials. Crops and animals are under continuing assault from a host of pests and diseases and from climatic vicissitudes. Maintenance of present levels of crop and animal production requires a sustained effort by plant and animal breeders to develop new varieties better able to resist this assault. Expanding agricultural production on the needed scale will require an even more intensive effort by breeders. To succeed in this, breeders must have access to a broad range of genetic material for developing more resistant and productive varieties of plants and animals. The plant and animal gene pool, therefore, is a critical resource for achievement of sustainable agriculture.
Most of the research on the supply of genetic resources for agriculture has dealt with plants. "Banks" to protect plant genetic materials have been set up by private firms and governments—most prominently, by the U.S. government—and by the Consultative Group on International Agricultural Research (CGIAR). These gene banks serve not only as repositories for plant genetic materials but also as distributors of the materials to plant breeders worldwide.
A study for the World Bank of the CGIAR system criticized some details of the system's performance but overall gave it high marks. Studies by World Bank researchers of the gene bank system as a whole pointed to some potentially serious weak spots in LDCs, particularly in Africa, but also concluded that in general the system is robust. The key question is whether the global gene bank system will continue to receive the support from national governments and international institutions that it will need to maintain that state of health. If it does, the plant genetic resource should be adequately protected. However, as the resource already is reasonably well managed, improvements in its management are unlikely to add much to its supply.
Gene banks are crucial for the development of hardier, more productive plant varieties; the question is whether the global gene bank system will receive the support needed to maintain its present health.
Knowledge. Given the present state of knowledge, the above discussion points to the conclusion that the potential supplies of energy, land, water, climate, and genetic resources would be quite inadequate to meet the prospective increase in global demand for food and fiber at acceptable economic and environmental costs. The implication is that most of the burden of sustainably meeting future demand must be carried by increasing the productivity of these combined resources. Achieving the necessary increases in productivity will require a substantial increase in the social capital represented by knowledge of agricultural production embedded in people, technology, and institutions.
Thus the critical question for agricultural sustainability is whether the global supply of knowledge can be expanded on the requisite scale. Although the answer must be uncertain, there are grounds for optimism. Compared with the other resources, the supply of knowledge about agricultural production is subject to few physical constraints. Knowledge accumulates; it is never used up and, in today's world, it is quickly and cheaply transmitted to the remotest regions of the globe. Reflecting these characteristics, agricultural knowledge has grown enormously over the last several decades and has accounted for most of the 2.5- to 3.0-fold increase in global agricultural production since the end of World War II. The international agricultural research system and the national agricultural research systems in more developed countries appear up to the future task if they continue to get adequate financial support. Private firms in those countries also are promising sources of new knowledge—for example, in biotechnology. Capacity to expand knowledge also is well developed in Asia, but is less satisfactory in Latin America, and least satisfactory in Africa. This capacity must be increased. In addition, agricultural research institutions will have to focus more on technologies and practices less dependent on irrigation and on fossil fuels, and more friendly to the environment than those now in common use.
Governments all around the world are moving toward greater use of agricultural markets, and this will strengthen farmers' incentives to use the new knowledge as it becomes available. The governments of many LDCs, however, have consistently underinvested in the education of rural people. This potentially serious obstacle to the needed expansion in knowledge must be overcome.
Expanding knowledge on the scale needed to achieve a sustainable agricultural system 2.5 to 3.0 times as large as the present one poses a formidable challenge to the global community. The historical record suggests that the challenge can be met. The potential consequences of failure provide perhaps the strongest assurance that it will be.
Pierre R. Crosson is a senior fellow in the Energy and Natural Resources Division at RFF.
A version of this article appeared in print in the January 1992 issue of Resources magazine.
A version of this article appeared in print in the January 1992 issue of Resources magazine.
