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Technological Trajectories and the Human Environment. 1997. Pp. 185-198. Washington, DC: National Academy Press. Sustaining the Human Environment: The Next Two Hundred Years CHAUNCEY STARR It is surely presumptuous to look into the two-hundred-year future of this changing world. Yet the questions we pose today about sustaining the world's habitability, the environment, and the quality of life of its human population force us to stretch our thinking in time. A society takes a half century to incorporate major technological changes into basic systems such as energy and transport, perhaps a century or more to modify substantially its cultural values, and many centuries to reconcile historically embedded ethnic and religious differences. A two-century scenario may provoke useful thoughts on the likely implications of present global trajectories and apparent choices. With such ponderous response times, today's societal institutions strain to accommodate the pressures arising from diverse forces. The global population has doubled in forty years and may double again in seventy-five more. Global economic output doubles about every thirty years, inevitably with an increased demand on our natural resources and a greater impact on the environment. New technologies that significantly transform goods and services now seem to appear roughly every twenty years. More slowly, governments and cultures adjust and restructure. The visible consequences of this mismatch in the dynamics of forced change and social restructuring have been highlighted by the various environmental movements. Environmentalists emphasize both today's costs of growth and the dismal implications for the future. How habitable will Earth be? Can ecosystems endure the projected pressures? What will be the resultant quality of life for the world's human population? The popular, gloomy response to these questions discounts the continuing 185
186 CHA UNCEY STARR positive contributions of science and technology, which have created a large share of today's global resources and life-style options. Many resources currently available would not be accessible or even recognized with the technology of a century or two ago. It is reasonable to ask, therefore, what might new technology contribute to our perceptions of global habitability, sustainability, and quality of life? I will briefly comment on these three concepts; look at the likely numbers of people, their food, water, and energy; and then discuss where they may live in a scientifically and technologically dynamic setting. HABITABILITY In its conventional sense, habitability implies: (1J the availability of the means for human survival, namely, food, water, and shelter from climate ex- tremes; (2) physical security from the threats of humanity and nature; (3) social security and stability in human relationships; and (4) a foreseeable continuum of the above. The majority of the world's population has long considered these goals adequate, even though they exceed the reach of many today. A few also consider amenities that make life pleasurable a sophisticated necessity. The expansion of "habitability" to include also the preservation of ecosys- tems apart from the value they provide to people assumes an answer to the philosophical question about the equitable treatment of all living things, of which humanity is but one (see Meyer-Abich, this volume). This essay will deal only with an anthropocentric view, but even that one-sided perspective obviously requires a sustaining relationship between humanity and the rest of nature. SUSTAINABILITY Assuming humanity and nature are separable entities, the environmentalist's usual definition of sustainability is development that consumes nature's divi- dends without impairing nature's capital. This ideal cannot be realized because, without humans, nature's dividends are already fully reinvested in the mainte- nance of nature's capital. Obviously all human activity intrudes and makes de- mands on nature's resources, both its dividends and its capital. Increasing intru- sion seems inevitable with an increasing global population. Even if the use of dividends and capital could be stabilized, it would imply a zero-sum game of distributing fixed natural resources among people's regional demands for habit- ability and life-style. A dynamic, turbulent, competitive, and growing world popu- lation will likely find such a definition of sustainability too confining. Govern- ments, including democracies such as the United States, so far show no success in achieving politically accepted zero-sum stability in national planning. What would be a more viable concept of sustainability? Could it be the minimizing of progressive environmental degradation? Or the preserving of ex- isting biotic resources for future populations? A case can be made for each.
SUSTAINING THE HUMAN ENVIRONMENT 187 Specific examples of their merit for environmental well-being abound, and their proponents use them to illustrate the urgency of action to achieve their view of sustainability. Interestingly, these somewhat diverse concepts share roots whose strength is rarely examined. They all start with the finiteness of the planet. It therefore follows that the planet's natural resources must also be finite. It is said these are being consumed at an expanding rate as the world's population and economy grow. Thus, Earth's resources of minerals, water, air, and biota will be depleted by the unrestrained increase in people's activities, and if this increase is allowed to continue unmodified, catastrophes will eventually destroy any sustainable sym- biosis of people and the rest of nature. Finally, the confluence of the exponential trends of population growth and resource depletion could be globally devastating. This qualitative logic leads to the common conclusion that the present gen- eration of decisionmakers should act responsibly through their various govern- ments to mandate the constraints on people's behavior necessary to avoid the pending catastrophes. So, as this reasoning goes, unless we act quickly and strin- gently, our future generations will successively face rapid deterioration in their quality of life. And, of course, our ethical responsibility to protect our children, and their children, requires sacrifice today for this purpose. These are powerful rhetorical arguments, and their simplicity leads to a standard manifesto appli- cable to all the presumed evils. This apparently logical sequence depicting environmental threats routinely provides the preamble to the massive literature on public policy relating to the environment and its sustainability. The absence of credible, quantitative charac- terizations of Earth's resources likely to be available for coming centuries, which may be compared with the range of future global demand, makes the arguments more compelling. The evolving availability of the resources and the efficiency of their use globally are usually neglected. Also absent is the potential for restora- tion of fauna and flora on a regional basis, such as through forestry. We are thus left with a vision of a likely worldwide degradation in the quality of life, though both timing and magnitude remain uncertain. The many specific examples of degradation that we see today reinforce this vision. We do not know whether these are significant early indicators of global trends or local failures to be ex- pected in a turbulent world. Fundamentally, these arguments provide the moral stiffening for much of the political activism aimed at persuading government to mandate actions to protect nature's future. The demand for centralized decision-making to limit the role of markets in which individual self-interest might dominate often accompanies this view. Implicit is a distrust of lay judgment in the marketplace of economic, technical, and social options. This distrust arises in part from a fear that the public reacts only when threats become highly visible or advanced, and that delayed action will fail to protect the environment. Such an environmentalist mixture of assumed prescience and virtuous political autocracy has provoked much contro
88 CHA UNCEY STARR versy in scientific circles, as well as some popular and political backlash. In view of the real uncertainties in the science underlying most long-range environmental concerns and the intense competition among pressing social needs, this debate will likely persist. If one seeks compatibility with the agenda of most of the world-in which people have primacy the appropriate concept of sustainability emphasizes the efficient use of all natural resources while seeking simultaneously to minimize avoidable degradation. The globally overriding societal concern is the long-term improvement in the quality of life. Such a broad dynamic concept makes the power of the human brain the crucial renewable resource, to be applied to the management and development of natural resources necessary for human better ment. This last view of sustainability recognizes practically the revealed priorities of most societies worldwide. It implies a major role for growing technical skills in resource development, management, and use. Many current resources result directly from technical skill, for example, photovoltaic energy, deep oil, desali- nated water, and synthetic materials. QUALITY OF LIFE Quality of life for the world's people incorporates both the habitability con- cerns about fitness for life and the sustainability concerns about balancing present and future well-being. The concepts of habitability and quality of life are merged at the outset and can separate only after the habitability needs are met. The concept of a societal quality of life is highly subjective and personal, although a few criteria are generally accepted. Often cited are a low level of infant mortality and long life expectancy the beginning and the end of the human span. These aggregate the effects of many social and environmental factors, each of which deserves public attention because of the high priority of health. Another generally accepted criterion is education, which is roughly indicated by the literacy rate of population groups. This rate perhaps tells more about societal priorities, egalitarianism, and economic status. Literacy opens the door to the vast knowledge resources of the world and has been a requirement for a modern society. However, it is arrogant to presume that illiteracy necessarily leads to dissatisfaction with the quality of life, as is demonstrated by the happy members of many non-literate, isolated groups. It is their interaction with modern societies that creates the desire for literacy as an important component of their quality of life. Rarely measured, but often mentioned, are the needs of the psyche-for freedom in all its aspects, choice in life-style, the beauty of nature, the arts, and the pleasures of recreation. This complex of individual priorities matters more as the other quality-of-life needs are met. This situation describes about a fourth of the world's population, particularly its more affluent members who can more
SUSTAINING THE HUMAN ENVIRONMENT 189 easily afford a long-range view. It is the group that most visibly and vocally cares about future global trends. It is also the group that most willingly accepts the marginal sacrifices and constraints suggested for mitigation of the undesirable and uncertain outcomes that might develop in the coming centuries, in the belief that the constraints would help. THE NEXT TWO HUNDRED YEARS For decades the debate over the urgency and content of policies intended to save the world from future devastation has been framed primarily by doomsayers with the rhetorical certitudes suggested above. I believe it is important to temper such prognostications with a touch of reality. Societies react to threats with a combination of actions to reduce their probability and severity, usually very slowly. Premature or unwise actions in anticipating threats may themselves lead to catastrophes. For example, the obsolescent Maginot Line, designed to protect against German tactics and equipment of World War I, left France defenseless (yet confident) at the start of World War II. Policies and investments are rapidly outmoded, rendered ineffective by changing systems, and may actually inhibit the best responses provided by new technology. Nevertheless, early preventive actions with today's technology sometimes seem appropriate when threats be- come evident. How do we gauge our timing and strategies when all we have to go on is the current information base? This is the classic problem of decision- making under uncertainty, and it is interesting to approach it as such. Let us now consider a plausible global development for the next two hundred years on the basis of today's knowledge, hindsight, and foresight. Hindsight teaches us not to be too confident. A recent book looked at 1993 as it was foreseen in 1893 (Walter, 19921. Except for a few forecasts, such as the growth of the telephone and cities, the great minds of 1893 failed to envisage 1993. Impor- tant technological, economic, and political changes were mostly unanticipated. Perhaps we can do no better today, but we should try, using this past century's experience, to foresee the world realistically rather than as we would like it to be. Population First, consider human population. A thousand years ago the global popula- tion was in a period of rough stability at about three hundred million, one person for every twenty today. By the seventeenth century, for many reasons including the onset of productive technologies, human numbers started to grow with a doubling time of about two hundred years. A century ago, global population growth had a doubling time of one hundred years. The rate peaked around 1970 at about thirty-five years. By the middle of the next century, the United Nations projects a global population of more than ten billion. Even if a global fertility reduction program instituted today could quickly reach and maintain a doubling
90 CHA UNCEY STARR time of seventy-five years, the population would increase sixfold to thirty-six billion by the year 2200. Some social or Malthusian limits seem likely to enforce stabilization in advance of this overwhelming number, although no convincing logic exists for a particular lower number. I judge hopefully that by the year 2200 the world's population might level off at three times the present, that is, about fifteen billion. Most of the intervening growth will be in the less-developed countries, where children are needed for cheap labor. Population growth has generally slowed with economic growth, so bettering the economies of the less- may hold the global population to fifteen billion. Can we and ener~V. the basic physical needs, for such a population? developed countries provide food, water, ~ _ =, Food No technical or resource obstacle inhibits a threefold or more increase in the world's food production. In the industrial countries, only a small fraction of the population is needed to produce the food, and about 10 percent is involved in its processing and distribution. The work force required is thus not a limitation. At present, more than half the food grown in less-developed regions is lost through spoilage, so the delivered food supply could be roughly doubled by using modern refrigerated transport and preservation techniques such as canning, dehydration, freezing, and irradiation. Doubling arable land globally is not a limitation if reliable water for irrigation is available. In fact, with irrigation, the present agri- cultural lands would be sufficient to double the world's food production. The crucial issues are the availability of water and energy to support the growing, processing, and distribution systems, and perhaps unwanted side effects from intensive production (see Waggoner, this volume). Water Water is both the world's most valuable and most wasted resource. Globally abundant but unevenly distributed, everyone understands its essentiality, but few understand its comparative worth except those faced with a scarcity. When water becomes scarce, use becomes efficient. Although some countries now partially accept the concept of regional management of the water supply, international and continental management remains novel. Yet this approach must be taken if the water needs of the next two hundred years, and for a population of fifteen billion, are to be met. The time scale for effective investment requires long-term inter- generational statesmanship and commitment. The problem is not the availability of technology or water. The quantitative aspects of the water supply have been widely studied and, although complex for specific regions, can be viewed more simply on a global basis. Nature annually contributes in fresh water to the world's continents about ten times the world's water use for all purposes. On average, about 70 percent
SUSTAINING THE HUMAN ENVIRONMENT 191 flows to the sea in seasonal floods; even if some could be captured, its storage might be an insuperable problem. Of the 30 percent that is theoretically usable, only about two-thirds is reachable from inhabited areas, so our potential global resource is, therefore, 20 percent of nature's original provision. Double the present world usage, will this amount suffice when the global population increases three- fold? Obviously, in the next two centuries the efficient use of water, its manage- ment, and the technology of recycling and desalination must all take part in achieving an adequate water supply. The present use of the world's water breaks down as follows: approximately 63 percent for agriculture, 25 percent for industry, 7 percent for cities, and about 5 percent for system losses. Drinking demands a very minor share of water. In the United States the present distribution of the managed water supply works out to about 47 percent for power-plant cooling, 34 percent for irrigation, 10 percent for municipal and domestic use, 7 percent for manufacturing, and 2 percent for losses. Of these US uses, about one-fourth disappears through evaporation, tran- spiration, and product inclusion, leaving about three-fourths that is theoretically recoverable for recycling. The bulk of the cooling water in power plants already returns to rivers and lakes. So, in the United States, about 17 percent remains available for recycling from municipalities and industries. Agriculture not only uses most of the world's water, it is also the most profligate. Crops actually take up only about a third of the water used for irriga- tion; the rest is lost. Microirrigation techniques can now reduce most of these losses. In the United States this would release about 20 percent of the managed water supply for other uses. Industrial and municipal use can be significantly reduced by recycling wastewater. That is feasible, however, only if the cost of removing the pollutants is not too high. Within manufacturing processes, such internal recycling may be relatively inexpensive. Strategically and economically, agricultural and fertilizer runoff, human waste, and industrial effluent offer the best opportunity to minimize pollution. Dealing with these at the sources rather than at the points of reuse lessens costs. With careful management, investment in technological aids, and political skill, the water needs of a global population of fifteen billion could be met. Water already stresses many localities today, and action in these areas could demon- strate possible strategies. If water is valued highly enough, several conservation and supply options arise, such as more efficient water use in agriculture. Conven- tional aqueducts can bring water to people in need, or, conversely, people can migrate to water sources. Capturing and storing river runoff has a long history and certainly can be expanded, but not without some ecological cost. Construct- ing water infrastructures and changing water policies can take decades- raising again the problem of response times mentioned at the outset of this essay. The ocean offers a final abundant source, and desalination will always be a technical option for fresh water if energy is available. For numerous US seaside communities, the cost today of desalination often roughly matches that of pumped
92 CHAUNCEY STARR aqueduct water, but the electricity demand is large for both about a 25 percent increase in the average electricity load for a seaside city. All the technical options for increasing the water supply to the consumer require substantial energy inputs, mostly in the form of electricity. The next centuries will intimately link long-range water and energy strategies. Energy In their search for economic growth, today's less-developed countries (LDCs) will largely determine the future global energy use. Per capita energy growth is strongly associated with economic growth. Per capita, LDC residents now use one-fifteenth of the US level, while the global average per capita of all countries is one-fifth of the current US level. In two hundred years the global average might reach today's US level, with some countries naturally still lagging well behind the average. This growth works out to a rate of 1.4 percent per year, a modest expectation for global economic growth. Threefold population and five- fold per capita energy increases would together multiply global energy demand 15 times. Even if efficiency improvements cut in half this level of energy de- mand, a 7.5-times increase still boggles the mind. However, in the past two hundred years, annual global energy use has in- creased approximately 50 times, primarily through the use of mineral fuels. From this perspective, an increase of 7.5 times in the next two hundred years may be a modest projection and challenge. We already foresee with some confidence more than a 2.5-fold multiplication in global energy demand from the present level by the year 2060 unless global economic growth is substantially suppressed. The multiple is less significant than its implications. The notion promoted by some environmentalists that global energy demand can be stabilized indefinitely at present levels is manifestly unrealistic, unless they concomitantly condemn most of the world's people to perpetual poverty. In two hundred years all fossil fuels will still be available but more costly, as less-accessible geologic reserves are developed. Recall that global energy con- sumption fifty years ago was about one-fifth of today's consumption, and the perception of economically recoverable resources, especially for oil, was also much more limited than today's. Many experts of that era predicted a serious scarcity of low-cost fuel during the 1960-1975 period. The history of natural gas and oil predictions in the United States illustrates the fallibility of current esti- mates of reserves and resources. During World War I, the US government issued public notices that the demand for natural gas was exceeding the supply and warned that a return to expensive manufactured gas loomed. In 1920 the US Geological Survey predicted that all oil reserves would be depleted in fourteen years. By 1960, for every barrel believed available in 1920, eight had been extracted and five more had been proven to exist. In 1974 the Federal Power Commission stated categorically that the United States was reaching down to the
SUSTAINING THE HUMAN ENVIRONMENT 193 "dregs" of its natural gas resources with "drastic" and "momentous" implica- tions. This incorrect assessment formed one basis for the Carter administration's decision to restrict gas as a fuel for electricity generation, an action reversed a decade later in view of the obvious and continuing abundance of gas. In fact, gas is now often the first choice for electricity generation, economically and environ- mentally. Fuel resources are not a static quantity. The technology of resource explora- tion, development, and extraction continuously improves in response to eco- nomic incentives, thus avoiding the scarcity. The cost of oil and gas today is about the same as fifty years ago, and proven reserves have doubled in spite of massive interim production. Nevertheless, today's known oil and gas reserves appear inadequate to meet all global energy demand for the next two hundred years. Based on atmospheric oxygen as the by-product of eons of photosynthesis, Earth's fossil-fuel content, including coal, is estimated at roughly 30,000 times the world's present annual rate of consumption. Technology will make some of this additionally available in the next two centuries, by such measures as opening the resources of the deep-oceans' bottoms. Biomass fuels and hydropower, at their feasible limits, might provide as much as 20 percent of global energy demand by the year 2200 (i.e., equal to about 1.5 times today's global total energy demand) provided that they do not seriously compete for land with food and fiber production. The intermittent renewables, solar and wind, might provide another 20 percent, although they remain expen- sive, awaiting breakthroughs in the cost of energy storage. Growth in fossil-fuel and nuclear sources will supply the balance. Nuclear power (fission or fusion) may be the only source feasible for large-scale expansion because of its relative environmental cleanliness, in spite of the current public fear about its novel safety issues. Of course, in two hundred years we may discover some now-unknown source, or tap "hot rocks" from the Earth's mantle, or focus solar space mirrors on Earth collectors, or invent and build a new energy storage or global supercon- ducting grid that makes solar power more important. Such speculations titillate but cannot form the basis for responsible long-range strategies today. In the last thousand years the only new primary energy source discovered was nuclear power. We should not expect that the next two centuries will provide another such discovery for use in a future "post-fossil fuel era," although we know that we cannot foresee many of the potentials of technology. As the economic development of the world continues, the fraction of primary energy used to make electricity as an intermediate will increase (see Ausubel and Marchetti, this volume). Electricity is the lifeblood of economic growth and technologic development in modern societies. More than a third of today's global primary energy input goes to electricity generation; in the next half century it is likely to rise to more than half, even with improved energy-to-electricity conver- sion efficiencies. New technologies create new electricity demands. For example,
94 CHA UNCEY STARR information systems, computers, and televisions now consume a sizable fraction of the electricity in industrial countries. Large-scale water desalination and puri- fication, large-scale recycling and reprocessing of materials, and nonpolluting transport are already visible areas for growth in electricity demand. Electrifica- tion will dominate global energy systems in two centuries. This energy scenario emphasizes our present social responsibility to main- tain viable roles for every feasible future energy option, especially nuclear power. No single fuel will satisfy needs for the next two centuries, and promoting a single path is irresponsible and grossly deceptive to the public. For example, to go beyond the generous solar and wind estimate given above, the energy storage costs (and their inefficiencies) would drain the world's capital resources. The end of superpower confrontation has outdated a strident antinuclear posture, prima- rily a by-product of historic antipathy to nuclear weapons and secondarily a gesture against a novel and rapidly growing technology whose risks needed to be better understood. With the prospect of long-term growth in energy demand, such ideological burdens should be removed from responsible long-term strategic per- ceptions and from the real problems of implementation facing all supply options. Societies inexorably need energy, particularly electricity. The challenge in the next two centuries is to supply this while meeting the constraints of economics, politics, environment, health, and safety. Human Settlements An acceptable quality of life encompasses much more than a bowl of food and a cup of water. We also care where we dwell. Can the world make room for fifteen billion people? Land space is obviously ample if one considers the huge unoccupied areas of the world, excluding the polar ice caps. However, these areas are empty because people consider them uninhabitable, usually due to a lack of water or to climate extremes. At some cost, as discussed earlier, we can mitigate both of these limitations. Whether societies will make investments to open new lands for major settlements remains uncertain. Water converted large areas of California from semidesert to farms and cities. This sort of land expansion could surely continue to accommodate agriculture or popular climatic and scenic pref erences. The greatest shift in settlement patterns continues to be urbanization. As agriculture industrializes, the fraction of a country's population working in the fields decreases from as much as 85 percent to 3 percent or so. The resulting migration has created a strategic dilemma. Almost 50 percent of the world's people live in urban centers. About 60 percent of the North American population lives in cities of more than a million people. On the one hand, ugly, land-eating "urban sprawl" describes the resulting enlargement of many of the cities. On the other hand, the negative effects of crowding on the urban quality of life also show
SUSTAINING THE HUMAN ENVIRONMENT 195 in the high-density center cities. The dilemmas will worsen with more population growth unless new trends in city life-style and design develop. Population density, a crucial factor, varies greatly among cities. Most of the cities in the United States and Europe are of similar densities, probably because of their similar architectural concepts: New York is typical, with about eleven thousand people per square mile. Population density in Hong Kong is 21 times greater than New York; Jakarta and Bombay 11 times; Cairo 9 times; Mexico City 3.5 times; and Tokyo only 2 times, although with thirty million people (about twice the number of metropolitan New York), it is the largest city in the world. These cities are growing at annual rates of from 1 to 3 percent, mostly by expansion at the fringes. If present trends continue, about 80 percent of the world's threefold population increase during the next centuries will be concen- trated in large cities a fivefold increase of urban population. Will this raise density or"sprawl"? Two opposite strategies become evident in response to the problem. The first is technology-based centralization; the second is counterurbanization. Where land is precious, as in Japan, the first is being pursued through many super-high-rise buildings. The population of Tokyo equals that of California, but it is crowded into less than 1 percent of California's area. As another measure, Tokyo has 2.7 times the population of Los Angeles in about the same area. The Japanese seek relief by constructing super-high-rise buildings with integral urban services, so that they work as minicities. One extreme proposal is for a five-hundred-story high rise (5 times the height of the World Trade Center in New York) that could house more than one hundred thousand people. Japan already has both ski slopes and bathing beaches enclosed by huge domed structures (see Ausubel, this vol- ume). In many big cities, high-rise apartment and office buildings are replacing low-level homes and shops. They also pose potentially costly civic burdens. Because of their high population density the buildings are vulnerable to the catastrophic effects of major equipment failures, and they create complex de- mands for traffic, policing, fire, and other services for the city of which they are a part. The response to the terrorist bombing of the World Trade Center in New York exemplifies these problems. The historic motivation for continued urban- ization arises from the benefits of juxtaposing important facilities and services, such as large markets, hospitals and health services, theaters, educational institu- tions, and administrative services. The time value of travel for these services (their convenience) seems most important. More recently, technology is stimulating the second option counterurban- ization. Telecommunication, both verbal and visual, is becoming simpler and more prevalent, so that any service that does not require physical contact can be made available at any distance with no delay and at modest cost. High-speed roads, rails, and airways can shorten travel times for physical exchanges. The technology of transport is the key to counterurbanization. For example, networks
96 CHA UNCEY STARR of high-speed electric trains could spread development over regions rather than concentrate it in one city. Trains dominated in the early l900s but were overcome by the popularity of the automobile, which provided faster door-to-door travel. National resources were invested in roads rather than in rails. The technology of high-speed rail systems, and perhaps improved helicopter or vertical takeoff flight, will make these important modes of travel in the coming centuries. In the absence of fast means of penetrating the center city, the trend will grow for subcities at the periphery of large centers, often ranging into the rural areas. A better quality of life at a lower economic cost has made these increas- ingly attractive relative to urban living. As numerous subcities develop around adjacent urban centers, they overlap into a regional megalopolis of relatively low population density, as in the northeastern United States. This counterurbanization has been further stimulated by the increasing urban disamenities of social and environmental origin, which detract from the historically high productivity of urban living. Roads will never become obsolete, and they can also encourage counterurbanization. Perimeter loops around the big urban centers have had star- tling effects in the past several decades. Wherever these perimeter loops intersect a radial road from the center, new communities, businesses, and manufacturing have developed. These areas then become the centers of smaller clusters. The most recent urban road systems include both an inner loop and an outer loop, as well as intersecting radials. Apparently a road system that minimizes travel time from outlying communities to urban facilities encourages decentralization of the population. The spread provides the several amenities common to suburban liv- ing. From a national resource perspective, the requisite travel infrastructure may be a desirable investment. But it fosters a continued reliance on the personal automobile rather than on public transport. Is this pattern desirable for the next two centuries from the viewpoints of energy resources and the environment? Perhaps the electric vehicle and nuclear power can resolve the question. The influence of technologic changes in shaping human settlements is clear. Looking forward two centuries, the threefold increase in global population poses the question of which strategies and patterns should be encouraged. Both urban minicities and counterurbanization subcities will continue to have available in- creasing technologic options and capabilities. Is it wise to support them? Should we encourage a life-style predominantly under covered domes, in a high-tech environment, shielded from nature's extremes? Should this trend be accepted as inevitable? Both of the long-range regional strategies will undoubtedly be pursued. Both require large-scale planning and investment. A cynic might comment that a demo- cratic society is rarely capable of deciding between such alternatives and that both will be followed until one haphazardly becomes the choice. A practical observer would note that the urban choices of the past endure for a very long time, as evidenced by the remnants of early transport systems, and that the free
SUSTAINING THE HUMAN ENVIRONMENT 197 competition of alternative developments does not ever exist. With diverse mo- tives, governments have always intervened to support one of the prevailing con- cepts. The world's major cities show the persistent remnants of errant favors. In light of the worldwide trend for people to drift to urban centers, the forms that such centers should eventually seek warrants much consideration. In these mat- ters strategies are made, either explicitly or implicitly, by the ongoing decisions of governing bodies about budgets, regulations, zoning, and standards, as well as by the emergence of technical possibilities. OVERVIEW This attempt to foresee the major constraints on global societies in the next two hundred years and how technologies may lift them touches on only the most obvious. On a global basis, natural resources do not appear as barriers to a habitable and sustainable world. However, social, political, and economic ob- stacles abound. Some regional management will always be needed to ensure clean air and water, unpolluted food, and physical security. Technologies with which to meet these needs exist today. The shared nature of the needs clearly requires government leadership to protect the common interest. The systems providing food, water, energy, and habitat depend on a mix of choices by individuals, enterprises, and government. The final acceptance or rejection of goods and services is made by individuals. The options are limited by the outcomes of government constraints that are placed upon the development of alternatives. These long-term choices epitomize the philosophical dichotomy be- tween those who believe in the efficacy of government planning by `'command and control" and those who believe that "free markets," with minimal govern- ment constraints, will result in optimal economic and technical development. Once a government intervenes to set constraints, presumably in the public inter- est, the field for free competition is no longer level, if it ever was, and some options will be inequitably treated. However, ample history of damage to the common resources of all, such as air, water, and environment, indicates that truly unconstrained free competition tends to focus on short-term values and neglects the long term. Moreover, we know that even with the best of intentions most decisionmakers, public and private, are unable to make choices today that are likely to be adequate for a highly uncertain future. The balancing of minimal government intervention with some cautionary constraints on free economic competition is the obvious goal. Achieving that balance is a complex political process with uncertain outcomes, particularly in the democratic political systems that we all cherish. Achieving the ideal of government by an informed public is hard when the information base for choices is usually uncertain, and winners and losers are involved. I have not dealt with the substantial environmental impacts of the growing world population and economy, seen by many as major threats to both ecosys
98 CHA UNCEY STARR terns and human health. They seem to me within the capability of technology, today's and tomorrow's, to manage during the next two hundred years and there- fore matter less for our intergenerational accountability. Regarding present con- cerns that earn global rather than regional attention, I do not anticipate that issues such as climate change, ozone depletion, and loss of biodiversity will cause life-threatening crises. We should study, anticipate, and respond to them, as we do with global diseases. I expect that a succeeding global generation, with its basic survival needs met and with superior knowledge and resources to imple- ment technical options, will respond to such environmental issues by mitigation and adaptation if its own priorities at that time motivate it to do so. I have little faith in the wisdom of governments to choose correct long-term strategies, par- ticularly in light of the unforeseen stream of scientific and technical changes that usually make preventive interventions for such problems unsound and damaging. I do not believe in manipulating the options for future generations it presumes a certitude of foresight that no one has. Clearly this is a controversial view challenged by those fearful of environmental outcomes, uncertain as they may be. A scenario always represents the author's views, and this one is no excep- tion. I am an optimist about technology's ability to maintain the global availabil- ity of the resources needed to sustain a large population. I am a pessimist about the ability of elite "brain trusts," scientific or political, to plan globally much beyond the present. I am very pessimistic about the ability of world governments to formulate global plans centrally when they are deeply deficient in managing their own domestic issues. So, I urge minimal governmental interference in the management of global resources and maximum freedom for the development and use of technical options. The real threats to a habitable and sustainable world in the next two centuries arise from the continuing social turmoil associated with the relatively inflexible cultural and ethnic differences among people. The seventy-year campaign of the USSR to wipe out such differences apparently failed completely. If the past two centuries are indicative, the magic cure for self-destructive social conflict has not been found. The technologist looks for clean water and air, sanitary sewers, and security from nature's blows. All these contributions to the habitability of the planet are quickly negated by the misery of wars and social conflicts. Universal economic prosperity is often suggested as the simple cure. It would certainly help, but is it sufficient? It seems that an optimistic sociologist and an optimistic economist are necessary to bolster my technological optimism for a globally happy future. REFERENCE Walter, D., ed. 1992. Today Then: America's Best Minds Look 100 Years into the Future on the Occasion of the 1893 World's Columbian Exposition. Helena, Mont.: American & World Geographic Publishing.