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1 Consumption as a Problem for Environmental Science Paul C. Stern, Thomas Dietz, Vernon W. Ruttan Robert H. Socolow, and fames L. Sweeney For over two decades, the same frustrating exchange has been re- peated countless times in international policy circles. A government offi- cial or scientist from a wealthy country would make the following argu- ment: The world is threatened with environmental disaster because of the de- pletion of natural resources (or climate change, or the loss of biodiver- sity), and it cannot continue for long to support its rapidly growing human population. To preserve the environment for future generations, we need to move quickly to control global population growth, and we must concentrate the effort on the world's poorer countries, where the vast majority of the population growth is occurring. Government officials and scientists from low-income countries would typically respond this way: If the world is facing environmental disaster, it is not the fault of the poor, who use few resources. The fault must lie with the world's wealthy countries, where people consume the great bulk of the world's natural resources and energy and cause the great bulk of its environ- mental degradation. We need to curtail overconsumption in the rich countries, which use far more than their fair share, both in order to preserve the environment and to allow the poorest people on earth to achieve an acceptable standard of living. Both parties to this stylized debate agree about the importance of acting to reverse environmental degradation in the world and of finding 1

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2 ENVIRONMENTALLY SIGNIFICANT CONSUMPTION development paths that preserve environmental quality. They also agree that knowing what action to take requires an understanding of the causes of environmental degradation. They disagree, of course, on what is the correct understanding. The disagreement is noteworthy in two respects: the "either-or" fram- ing of the problem (either environmental threats result from overpopula- tion by the poor or overconsumption by the rich), and the limited role played in the discussions by scientific analysis of human-environment interactions. In contrast to the major international efforts that have been mounted to understand the biogeochemical processes that account for global climate change, acid deposition, ozone depletion, loss of biodiversity, and other environmental threats, relatively little scientific attention has been given to understanding the economic, social, cultural, and institutional processes that set such anthropogenic environmental changes in motion. It is well known, for instance, that world population growth is concentrated in the poorer countries and that consumption of key resources such as oil is concentrated in the richer countries. Too often, however, analysis of the environmental impacts of human activity has not gone much farther than this, and the policy debate has suffered as a result. Governments and citizens around the world need far more detailed knowledge to effectively anticipate and cope with environmental threats. Specifically, they need empirical analysis in two areas: the par- ticular human choices and actions most responsible for adverse changes in the biophysical environment and the potential for addressing the threats by affecting those choices and actions. This is not to say that knowledge alone is sufficient for effective coping. Knowledge is neces- sary, but it is also necessary to reconcile interpretations of knowledge, to forge agreements on how to act in spite of uncertainty and conflicting values and interests, to command resources, and so forth. Scientists have long recognized that the magnitude of anthropogenic environmental changes depends on both human population size and on what this population does. This relationship was conceptualized in the early 1970s as follows: I = P x A x T. in which I represents environmental impact, P represents population, A the economic output per capita is usually interpreted as a measure of affluence, and T the environmental impact per unit of economic out- put is sometimes interpreted as a characteristic of technology (Ehrlich and Holdren, 1971; Commoner, 1972; Holdren and Ehrlich, 1974~. As stated, this equation is a tautology: environmental impact equals population times (economic output per unit population) times (environ

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CONSUMPTION AS A PROBLEM FOR ENVIRONMENTAL SCIENCE 3 mental impact per unit economic output). However, the equation does suggest that one should consider at least three factors in analyzing an- thropogenic environmental changes: the population, some measure of activity per person, and some measure of the average impact of each unit of activity on the environment. This so-called IPAT identity has been used as a basis for analysis, but it must be treated with care. While it must hold mathematically, one cannot simply use the equation for prediction because these three factors do not develop independently of one another. For example, as per capita economic output increases in a society, that society may strive to reduce environmental impacts and succeed in de- creasing the environmental impact per unit of economic activity. Simi- larly, increasing population may alter the economic output per capita. The interdependencies of P. A, and T can seriously limit the usefulness of the equation, especially for analyses over long time periods. The IPAT formulation has also been controversial because of the way its terms have been interpreted. For instance, the interpretation of T as "technology" has been criticized for drawing attention away from the roles of social and economic institutions in environmental degradation. For a recent discus- sion of these issues, see Dietz and Rosa, 1994. With these caveats in mind, treating environmentally relevant human activity as a mathematical product is intuitively appealing because it re- duces the analytic problem to two factors: numbers of people (popula- tion), and the impact of the average person on the environment (some- times referred to as the impact of consumption). Population is by far the easier of the two concepts to study. Its units of measurement are obvious and there is an established scientific discipline, demography, that studies human population dynamics. Consumption, by contrast, has neither well- defined and accepted units of measurement nor a scientific community devoted to studying its dynamics. As noted in Chapter 2, it even lacks a shared definition that is useful for studying environmental effects. This book results from a workshop that brought together specialists from a variety of fields to discuss research on environmentally significant "consumption" and its causes, with special focus on the United States and other wealthy countries. Participants discussed research that aimed to improve knowledge of consumption phenomena and thus to strengthen the knowledge basis for policy planning. This volume, like the workshop, attempts only a small step toward useful knowledge. It does not attempt to offer practical conclusions about how to alter consumption patterns or to definitively map the intellectual domain. In fact, as noted below, there are several active and relevant areas of research that are not discussed here. The volume does, however, demonstrate that environmentally sig- nificant consumption requires careful scientific analysis, and it tries to convey to the reader some of the excitement of taking a scientific ap

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4 ENVIRONMENTALLY SIGNIFICANT CONSUMPTION proach to the issue by noting the potential of some relatively untraveled but promising paths to new understanding. It points out some ways to pursue these research directions, and we hope it will stimulate action by researchers and research sponsors. FOUR CLASSES OF EMPIRICAL QUESTIONS The broad topic, "what each person does to the environment," di- vides fairly readily into four major classes of empirical questions, each of them researchable and each critical for understanding and controlling the environmental impacts of consumption. 1. Which human activities are the significant environmental disrupters? How environmentally significant is each activity, and in what ways is it destruc- tive? What have been the trends of these activities over time, and how may technological change and other forces affect those trends in the future? Some human activities are well known to be environmentally disrup- tive. Fossil energy consumption, the most obvious example, is a major contributor to global climate change, urban air pollution, and acid depo- sition. Mining and processing of metals, especially toxic heavy metals, pollutes water and threatens human health and ecological systems. Agri- cultural practices such as fertilization, irrigation, and the use of pesticides pollute water and alter the nitrogen and fresh water cycles. Many other human activities also have environmental significance. The first ques- tions about the environmental impacts of human activities concern which of these activities are important enough in terms of their environmental consequences to deserve serious and immediate attention and what kinds of impact each has. These questions have great practical importance. If the concern is to limit certain destructive environmental impacts of what people do, deci- sion makers need to know enough to set priorities among possible target activities, to understand the tradeoffs involved in targeting one set of activities rather than another, and to consider the potential environmen- tal impacts of the activities that might replace those the policy makers seek to control. These decision makers need to know which human ac- tivities are significantly disturbing environmental systems and which ac- tivities are likely to do so in the future. To respond to such conditions and possibilities, they need more detailed knowledge. For example, decision makers who want to protect an aquatic ecosystem need to know whether it would be more effective to reduce fertilization so that less nitrogen leaches off nearby farmland or to promote better soil conservation prac- tices to control the amount and timing of runoff. Those who want to

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CONSUMPTION AS A PROBLEM FOR ENVIRONMENTAL SCIENCE 5 reduce the environmental impact of the automobile industry need to con- sider the tradeoffs involved in building vehicles of less steel and more plastic. Lighter cars use less fuel and require less mining and smelting, but the life cycle of plastics has its own, possibly offsetting, environmen- tal effects. Decision makers also need to consider the secondary effects of possible policies. A decision to make all new cars lighter might induce some consumers to purchase light trucks instead of cars, thus undermin- ing the intended result. Addressing these questions requires, among other kinds of understanding, knowledge of the environmental effects of each kind of human activity that policy may affect. There are considerable bodies of relevant research on the environmental consequences of par- ticular human activities, on natural resource accounting, and on the incor- poration of environmental factors into national income accounts. These issues are not, however, the focus of this volume. 2. Who are the key actors responsible for the environmentally disruptive activities? Which of their actions are the important ones? To limit the environmental impact of any human activity, it is essen- tial to understand which types of individuals or organizations account for most of the activity and how the activity of interest fits into their overall purposes. A single environmental problem may result from different actors do- ing different kinds of things. For example, urban air pollution consists partly of ozone, much of which is a by-product of emissions from motor vehicles operated by individuals. But air pollution also consists partly of sulfur oxides, for which individual action bears little responsibility. Sul- fur oxides come largely from coal combustion, which in the United States is mainly an activity of large industrial organizations, especially electric utility companies. Thus, controlling air pollution may require the imple- mentation of very different policies, each suited to a particular class of actor and kind of activity. It is also important to know which of the things an actor does are environmentally important. For instance, if one wants to consider op- tions for reducing water consumption among residences in a municipal- ity, it is useful to know how much of that use is for watering lawns, filling pools, washing cars, bathing, washing, cooking, and other purposes, be- cause households may treat some of these uses as more essential than others or find some of them relatively easier to postpone. If a large pro- portion of water is used to do things that can be easily postponed, a time restriction may be an effective intervention; if a large proportion is for uses considered nonessential, a price incentive may be highly effective.

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6 ENVIRONMENTALLY SIGNIFICANT CONSUMPTION 3. What forces cause or explain environmentally disruptive actions ? Human activities that alter the environment respond to a mixture of social, economic, technological, political, and psychological forces. The example of energy use in residences illustrates the general situation. En- ergy use depends on multiple factors within households, including the number of people in the household and on whether any of them spend their days at home, which affect the demand for heating, cooling, and the services that appliances provide. It depends on household income, which affects the size of a dwelling and therefore its energy demand, and also affects the household's ability to invest in energy-efficient home technol- ogy, which can have a countervailing effect. The use of energy also de- pends on the age and sex of the occupants, which affect the desired ambi- ent temperature. And it depends on household members' desires for appliances; their attitudes, beliefs, and values concerning energy use, fru- gality, and various other matters; and even their cultural backgrounds. In addition, energy use depends on household technology and its relation to the physical environment: the appliances being used and their designs, the home's construction, its exposure to wind and weather, and its sur- rounding micro- and macroclimates. Household energy use is influenced by many additional factors as well, which create the context for key choices and actions in the house- hold. An obvious one is the price of energy, which is affected, in turn, by public policies of energy taxation and utility regulation, the competitive- ness of energy industries, advances in the technology of energy produc- tion and distribution, and perhaps the history of national energy produc- tion in the United States a long history of energy self-sufficiency may help explain the strength of the political forces that have for two decades stymied efforts to raise oil prices to help meet environmental objectives. Energy use is also affected in indirect but important ways by the standard practices of the home construction and appliance manufacturing indus- tries, by local building codes, and by the practices of home mortgage lenders, which may or may not offer financial benefits to the buyers of energy-efficient homes that cost less to maintain. Consumption is af- fected by tax incentives for home ownership because incentives make larger homes more affordable, and these homes use more energy. And energy use may also be affected by policies intended to influence it di- rectly, such as regulations governing appliance manufacture and the in- formation and financial incentives that governments and energy suppli- ers have sometimes offered to households to induce them to invest in energy efficiency. This long but incomplete list suggests several things: that an environ- mentally significant consumption activity like household energy use is

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CONSUMPTION AS A PROBLEM FOR ENVIRONMENTAL SCIENCE multiply determined; that the influences are of many kinds, both direct and indirect; that the many influences are interdependent, acting in combinations rather than additively; that it will take many disciplines working together to understand how they drive the phenomenon; and that the influences act on different time scales, with some, like the de- mand for heating and cooling, capable of changing in minutes, hours, and days, while others, like those affecting building construction, have effects that last for decades. In these respects, energy use is much like other environmentally relevant human activities and choices (National Research Council, 1992: Chapter 3~. Each of these choices and activities responds to multiple influences, yet for each, the causes are amenable to scientific study. 4. How can environmentally disruptive human activities be changed ? From a policy perspective, this question provides a sufficient motive for asking all the previous ones: if decision makers must contemplate changing environmentally disruptive activities, they need to understand the nature and causes of those activities. Knowing how to change envi- ronmentally significant activity, however, requires more than an under- standing of the causes. Those who would be influence agents need enough knowledge about how these activities might be changed to select effective options. Some knowledge already exists about the effects of particular kinds of intervention from studies of the diffusion of techno- logical innovation (for reviews of this literature see, e.g., Rogers, 1995; Ruttan, 1996~; the effects of environmental regulation, monetary induce- ments and penalties, and other incentive-based interventions (e.g., Baumol and Oates, 1988; Cropper and Oates, 1992; Geller et al., 1982; Nichols, 1984; Tietenberg, 1985~; the effectiveness of information in promoting proenvironmental behavior change (e.g., Katzev and Johnson, 1987; Gardner and Stern, 1996~; the role of social movements in environmental change (e.g., Brulle, 1996; Dunlap and Mertig, 1992~; and institutional strategies for environmental management (e.g., Ostrom, 1990; North, 1994~. Much more work needs to be done, however, to develop these insights further, to compare the effectiveness of different types of inter- ventions against each other, and to understand the potential synergisms that may arise from combining different types within a single, coordi- nated intervention (e.g., Gardner and Stern, 1996:Chapter 7~. PURPOSES AND STRUCTURE OF THE BOOK This book, though inspired by policy makers' concerns about how to reduce "the environmental impacts of U.S. consumption," focuses on

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8 ENVIRONMENTALLY SIGNIFICANT CONSUMPTION building basic knowledge rather than directly on policy questions. Our concern is with understanding which human activities are of major envi- ronmental significance, what forces shape those activities, and what their trends have been and might become in the absence of policy intervention. This sort of understanding is essential for policy makers because it can help them define the important policy issues, anticipate needs for inter- vention, and identify appropriate targets for interventions. It is a large task to build such understanding, and our modest purpose here is to encourage progress in that direction. Consequently, we do not advocate policy strategies for controlling the environmental impacts of consump- tion or discuss the extensive literature on the effectiveness or social ac- ceptability of policies that have been proposed or enacted to accomplish that end. Much work has already been done on some issues important to un- derstanding environmentally significant consumption, and we do not at- tempt to summarize it here. The relevant areas that are already well developed or currently active include work on the effects of prices and other economic signals (e.g., Baumol and Oates, 1988; Cropper and Oates, 1992; Nichols, 1984), on trends toward "dematerialization" and "decar- bonization" in the economy (e.g., Herman et al., 1989; Nakicenovic, 1996; Wernick et al., 1996), on the potential for shifting materials flows from a linear pattern to a cyclic one that uses wastes as inputs to production (e.g., Allenby and Richards, 1994; Frosch, 1996; Socolow et al., 1994), on the environmental impacts of international trade (e.g., Runge, 1995; Runge et al., 1994), and on indicators that might allow systematic comparison of the environmental impacts of different kinds of human activity (e.g., Fava, 1991; National Research Council, 1994; Lave et al., 1995; Wackernagel and Rees, 1996~. This book touches on some of these areas but focuses prima- rily on two other things: it tries to suggest the outlines of a scientific field, "environmental impacts of consumption," that may someday bring to- gether these areas of work as well as additional areas within a coherent intellectual framework; and it presents illustrations of some of the other kinds of research, not yet well developed, that may eventually make im- portant contributions to that field. The book is intended for people who want to improve understanding of the human activities that constitute environmentally significant con- sumption: scientists in fields that can build this understanding and the organizations that might support their scientific work. It shows that, in addition to the knowledge that is already being developed, there are many critical questions that have barely begun to be addressed and, ac- cordingly, that there are major opportunities to build useful knowledge. We hope it captures some of the excitement of the workshop from which it came, in which people from many separate intellectual fields began to

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CONSUMPTION AS A PROBLEM FOR ENVIRONMENTAL SCIENCE 9 see their common interests, and that it encourages the exchange of ideas necessary to build the needed understanding. Scientific endeavors normally begin by adopting a working definition of the phenomenon to be examined, but the field of consumption and the environment has not yet made this step. As Paul Stern shows in Chapter 2, consumption is an ambiguous concept. It has precise and distinct mean- ings in physics, economics, and ecology and somewhat less precise mean- ings in sociology, but none of these corresponds to the usage in the phrase "environmental impacts of consumption." Stern discusses two defini- tions of consumption that might guide research on its environmental im- pacts and offers one of them as preferable. His analysis suggests the breadth of the field by noting a variety of open research questions that require attention from the social and natural sciences. Chapters 3 and 4 present brief reports, taken from presentations at the workshop, that suggest some interesting research directions. The reports in Chapter 3 address issues of measuring and tracking flows of materials and energy that are affected by human consumption activities; those in Chapter 4 concern the driving forces of environmentally signifi- cant consumption. The reports indicate some promising directions for research; in addition, each one includes numerous citations that can direct an interested reader farther into the particular domain of study. We see these reports as suggestive. They do not present a full menu of research opportunities but only a list of hors d'oeuvres. We hope these reports whet the appetites of researchers and research sponsors. Chapter 5 discusses how to set research priorities. It proposes an importance criterion for agenda setting: that top priority go to research on aspects of consumption with major environmental effects. This crite- rion suggests the strategy of identifying the most environmentally dis- ruptive human activities and then searching to explain them and to ac- count for how they affect the environment. The chapter examines this strategy in some detail, noting how some of the reports in Chapters 3 and 4 exemplify its use. The chapter also discusses two other ways to identify important research topics. One, which focuses on possible policy inter- ventions, is more useful for policy analysis than for basic understanding of consumption. The other begins with social phenomena and works through to their environmental implications. Although this last strategy can yield useful insights that might not come from a research program that starts with environmental changes, it places a burden of proof on the researcher to demonstrate that the environmental effects are important and not just plausible or theoretical.

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10 ENVIRONMENTALLY SIGNIFICANT CONSUMPTION REFERENCES Allenby, B., and D.J. Richards, eds. 1994 The Greening of Industrial Ecosystems. National Academy of Engineering. Wash- ington, D.C.: National Academy Press. Baumol, W.J., and W.E. Oates 1988 The Theory of Environmental Policy, 2nd ed. Cambridge, England: Cambridge University Press. Brulle, R.J. 1996 Environmental discourse and social movement organizations: A historical and rhetorical perspective on the development of U.S. environmental organizations. Commoner, B. Sociological Inquiry 66:58-83. 1972 The environmental cost of economic growth. Pp. 339-363 in Population, Resources, and the Environment. Washington, D.C.: U.S. Government Printing Office. Cropper, M.I., and W.E. Oates 1992 Environmental economics: A survey. Journal of Economic Literature 30:675-704. Dietz, T., and E.A. Rosa 1994 Rethinking the environmental impacts of population, affluence, and technology. Human Ecology Review 1:277-300. Dunlap, R.E., and A.G. Mertig 1992 The U.S. Environmental Movement, 1970-1990. Washington, D.C.: Taylor and Francis. Ehrlich, P.R., and J.P. Holdren 1971 Impact of population growth. Science 171:1212-1217. Fava, J.A., R. Denison, B. Jones, M. Curran, B. Vigon, S. Selke, and J. Barnum, eds. 1991 A Technical Framework for Life-Cycle Assessments. Washington, D.C.: Society for Environmental Toxicology and Chemistry. Frosch, R.A. 1996 Toward the end of waste: Reflections on a new ecology of industry. Daedalus 125~3~:199-212. Gardner, G.T., and P.C. Stern 1996 Environmental Problems and Human Behavior. Boston: Allyn and Bacon. Geller, E.S., R.A. Winett, and P.B. Everett 1982 Preserving the Environment: New Strategies for Behavior Change. New York: Pergamon. Herman, R., S.A. Ardekani, and J.A. Ausubel 1989 Dematerialization. Pp. 50-69 in J.H. Ausubel and H.E. Sladovich, eds., Technology and Environment. Advisory Committee on Technology and Society, National Academy of Engineering. Washington D.C.: National Academy Press. Holdren, J.P., and P.R. Ehrlich 1974 Human population and the global environment. American Scientist 62:282-292. Katzev, R.D., and T.R. Johnson 1987 Promoting Energy Conservation: An Analysis of Behavioral Research. Boulder, Colo. Westview. Lave, L.B., E. Cobas-Flores, C.T. Hendrickson, and F.C. McMichael 1995 Using input-output analysis to estimate economy-wide discharges. Environmen- tal Science and Technology 29:420A426A. Nakicenovic, N. 1996 Freeing energy from carbon. Daedalus 125~3~:95-112.

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CONSUMPTION AS A PROBLEM FOR ENVIRONMENTAL SCIENCE 11 National Research Council 1992 Global Environmental Change: Understanding the Human Dimensions. P.C. Stern, O.R. Young, and D. Druckman, eds. Committee on the Human Dimensions of Global Change. Washington, D.C.: National Academy Press. 1994 Assigning Economic Value to Natural Resources. Papers presented at the Workshop on Valuing Natural Capital for Sustainable Development, July 1993. Washing- ton, D.C.: National Academy Press. Nichols, A.L. 1984 Targeting Economic Incentives for Environmental Protection. Cambridge, Mass.: MIT Press. North, D.C. 1994 Constraints on institutional innovation: Transaction costs, incentive compatibil- ity, and historical considerations. Pp. 48-70 in V.W. Ruttan, ea., Agriculture Envi- ronment and Health: Sustainable Development in the 21st Century. Minneapolis: University of Minnesota Press. Ostrom, E. 1990 Governing the Commons: The Evolution of Institutions for Collective Action. Cam- bridge, England: Cambridge University Press. Rogers, E.M. 1995 Diffusion of Innovations, 4th ed. New York: Free Press. Runge, C.F. 1995 Trade, pollution, and environmental protection. Pp. 353-375 in D.W. Bromley, ea., The Handbook of Environmental Economics. Oxford, England: Blackwell. Runge, C.F., F. Ortalo-Magne, and P. Vande Kamp 1994 Free Trade, Protected Environment: Balancing Trade Liberalization and Environmental Interests. New York: Council on Foreign Relations. Ruttan, V.W. 1996 What happened to technology adoption-diffusion research? Sociologia Ruralis 36:1-24. Socolow, R., C. Andrews, F. Berkout, and V. Thomas, eds. 1994 Industrial Ecology and Global Change. Cambridge, England: Cambridge University Press. Tietenberg, T.H. 1985 Emissions Trading: An Exercise in Reforming Pollution Policy. Washington, D.C.: Resources for the Future. Wackernagel, M., and W. Rees 1996 Our Ecological Footprint. Gabriola Island, B.C., Canada: New Society Publishers. Wernick, I.K., R. Herman, S. Govind, and J.H. Ausubel 1996 Materialization and dematerialization: Measures and trends. Daedalus 125~3~:171- 198.