Policy Analysis Getting Serious about Sustainability THOMAS E. GRAEDEL* AND ROBERT J. KLEE Center for Industrial Ecology, School of Forestry and Environmental Studies, Yale University, 205 Prospect Street, New Haven, Connecticut 06511
Sustainability and sustainable development are catchwords that dominate today’s environmental science and policy discourse. It is easy to demonstrate that most of the activities of today’s industrial society are unsustainable. Unfortunately, much of the talk about sustainability lacks a basic understanding of what truly sustainable activity would be. To set sustainability as a target or goal for our industrial society, we must be able to quantify that target or goal. We propose four basic steps to begin this process for one aspect of sustainability, the rate of use of resources: (i) establish the available supply of the chosen resource; (ii) allocate the annual permissible supply according to a reasonable formula or market process; (iii) establish the “recaptureable” resource base; and (iv) derive the sustainable limiting rate of use and compare to the current rate of use. We apply these sustainability measurement methods to three common materials in industrial society: zinc, germanium, and greenhouse gases. These examples demonstrate that with some basic (although potentially controversial) assumptions, quantitative sustainable use goals can be set and current performance relative to those goals can be evaluated. The assumptions and approximates we have used are meant to stimulate thought and debate, beginning a long conversation on the measurement of sustainability.
Introduction Improved environmental performance in industry and society is a concept now a quarter-century old. Efforts in this regard have yielded much in the way of environmental improvement, but there are clear suggestions that the next generation of environmental policy needs to adopt a more holistic and systemic perspective (1). As approaches to this policy transition have been explored, there has been increasing use of the idea of sustainable development, as famously defined by the World Commission on Environment and Development: To “meet the needs of the present without compromising the ability of future generations to meet their own needs” (2). More recently, we have seen the word “sustainable” applied very broadly: in chemistry, engineering, agriculture, fishing, and comprehensive societal assessments (3-11). It is easy to demonstrate that the present use of the planet and its resources by humanity is unsustainable. Examples are provided by the World Commission on Environment and Development, the Board on Sustainable Development, and many others (2, 10). It is less clear how to demonstrate what * Corresponding author phone: (203)432-9733; fax: (203)432-5556; e-mail:
[email protected]. 10.1021/es0106016 CCC: $22.00 Published on Web 01/10/2002
2002 American Chemical Society
might be sustainable. Sustainability is a term that is readily agreed to be a desirable characteristic for humanity’s future, yet precisely what it means is open to considerable debate. As the Board on Sustainable Development notes, authors and organizations have taken quite different positions on what is to be sustained, for whom, and for how long (10). While there have been a few attempts to set perspectives for quantifying sustainability (e.g., refs 12-14), developing a logically constructed system for specifying numerical goals and targets has proven more difficult. Without numerical goals and targets, however, sustainability will remain a mere concept rather than a program capable of implementation. Numerical goals and targets must be functional across scalessfrom global to corporation to individualsif they are to be truly useful. Ultimately, we wish these metrics to indicate whether a particular product or a particular activity, in combination with all other products and activities, is within sustainability limits. Previous efforts at environmental metrics such as environmental load units (15), economics of ecosystem services (16), and composite evaluation (17) have had some success at evaluating aspects of global sustainability or corporate performance but not of cross-scale linkage. Without that linkage, sustainability cannot be more than an abstract idea for the corporate manager, the product designer, or the customer rather than a call to action. The definition of numerical goals, desirable rates of improvement, and plans to achieve those ultimate goals and rates must ultimately be the work of government and society at all levels. As a basis for these activities, however, environmental scientists, resource specialists, and industrial ecologists can set the framework by defining terms, evaluating options, and assessing possible actions. In this paper, we examine the ways in which goals and targets for several different types of resources might be addressed and what choices and challenges emerge from the exercise.
Concepts of Sustainability “Sustainability” and “sustainable development” are loaded words, arguably overused in today’s environmental discourse. These words have distinct meanings to social scientists, economists, ecologists, biologists, resource managers, and environmental scientists. The dictionary definition of “sustainable” sheds a little light, meaning “able to be kept up or prolonged”. However this strict dictionary definition of simply keeping up or prolonging our current situation is not, in our opinion, satisfactory. What we should collectively strive for is constant improvement and betterment of the human condition as well as the condition of the planet’s natural systems. The adage of “leaving the world better than you found it” should fit somewhere in the concept of sustainability, not simply maintaining an unsatisfactory status quo. “Development” is integrally linked to this notion of sustainability through betterment of the world. Development is not necessarily growth in terms of quantitative increases of size, scale, and physical dimensions; rather, development implies a qualitative improvement in structure and design, which need not be accompanied by increasing size or mass (18). As many of our examples for sustainability goals will show, getting better will be much more important than getting bigger in the coming decades. Furthermore, although not readily apparent from the World Commission on Environment and Development (2) definition, ultimate sustainability and truly equitable environmental policy will only be achieved by balancing economic, environmental, and equity concerns. VOL. 36, NO. 4, 2002 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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Many of today’s unquestionably unsustainable practices occur when one concernsthe economy, the environment, or the desire for equitysdominates the other two. In the end, what precisely are the things we wish to sustain? We posit that there are five, though people’s lists differ: (i) Holocene-style climate (thermal balance, ocean currents, etc.). (ii) Functioning planetary ecological systems (wetlands, forests, etc.). (iii) Stocks of resources. (iv) Earth’s organisms. (v) Political and economic stability with tolerable variations. The Board on Sustainable Development considers human survival and quality of life to be the only realistic way to approach sustainability and a couple of human generations to be the only realistic time scale. From that perspective, we must have planetary environmental, economic, and political systems that are basically stable (though within reasonable ranges of fluctuation) and whose driving forces (e.g., energy, resources, technological change, etc.) maintain themselves for at least half a century. An important perspective is that our extraction and use of resources must take into account the assimilative and restorative capacity of planetary systems disturbed by those activities.
Examples of Sustainability Planning How is one to approach the challenge of providing sustainability guidance in such a way that it can and will be implemented by nations, by cities, and by corporations, all with different cultural traditions and systems of governance? We explore in this section of the paper a few examples for nonrenewable resources, all potentially contentious, of how such guidance might be established and provided in such a way that the “journey toward sustainability” might begin. Most measures of planetary condition evolve over time. Our concern is not with their stability but with their value relative to a sustainability goal. Consider Figure 1a, which shows a hypothetical decrease in the abundance of an environmental resource with time. Once scientists establish the limit beyond which the system is unsustainable (admittedly not an easy task), any value not reaching that limit can be regarded as sustainable. Hence the solid line in Figure 1a is an example of a sustainable trend in the use of resources; the broken line an example of an unsustainable one. For an environmental stressor, the form of the curves is identical but inverted, as in Figure 1b. In a number of cases, it will be necessary to select a time horizon over which sustainability is to be evaluated. In accordance with the Board on Sustainable Development (10), we regard 50 yr (i.e., roughly two human generations) as a reasonable period for assessment. By most accounts, the next 50 yr will be crucial in determining long-term resource sustainability. Population will increase dramatically over the next 50 yr from 6 billion to perhaps 9 billion (19). According to the Intergovernmental Panel on Climate Change (IPCC), a discernible human-induced climate change on the order of 1-4 °C is likely to occur (20). And, commonly used industrial minerals and both oil and natural gas will become increasingly scarce over the next 50 yr (21). We further assume that resource consumption should be planned so that existing resources will last for 50 yr at current rates (but, as we discuss later, the targets should be recomputed every few years to reflect updated information). A 50-yr planning horizon allows time for substitution of other resources or the development of alternative ways of meeting the needs that are served by resource consumption. Once a resource of interest is chosen, we see four basic steps in establishing and evaluating a preliminary measure of sustainability. 524
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FIGURE 1. Conceptual forms of stable and sustainable systems. (a) The behavior of an environmental resource (for example, the supply of water) with time. The dashed line represents the limit (established by scientific study) below which the resource supply cannot go if the system is to remain sustainable. The solid curve is that for a sustainable system; the broken curve is that for an unsustainable system. (b) The behavior of an environmental stressor (for example, the atmospheric concentration of carbon dioxide) with time. The dashed line represents the limit (established by scientific study) that cannot be exceeded if the system is to remain sustainable. The solid curve is that for a sustainable system; the broken curve is that for an unsustainable system. (i) Establish the virgin material supply limit by calculating the amount of a resource that can be used per year if that resource is to last for 50 yr. To do so, one must first establish the known quantity of the resource available within the region of interest (the globe, a country, a state, etc.). For a nonrenewable resource this amount is termed the “reserve base”, defined as those resources that can be extracted at a profit plus resources that are known but are not presently economically viable (21). (ii) Allocate the virgin material supply according to a reasonable formula (such as, for example, allowing markets to perform the allocation or by dividing it equally among the global population). Throughout the following examples, we assume that the average global population over the next 50 yr will be 7.5 billion people. (iii) Establish the regional “recaptureable” resource base, which is the known quantity in stockpiles, landfills, etc. where it might reasonably be accessed. We assume that this resource can be replenished from existing stock in use at the current regional rate of recycling or reuse of the chosen material. (iv) Compare the current consumption rate to the sustainable limiting rate for that resource within the region being assessed.
CHART 1. Calculation of a Global Sustainable Limiting Rate of Zinc Consumption
Once this process is carried out, one can begin to speak intelligently and realistically about any necessary policy actions that might be needed to respond to excess consumption. Example 1: Sustainable Supplies of Zinc. To illustrate the approach, let us derive a sustainability limit for the use of zinc. Zinc, a fairly representative industrial mineral, is widely used by our modern technological society, yet known reserves suggest that it is in relatively short supply (21). About half of zinc production goes to make galvanized steel, in which a thin coating of zinc protects the underlying steel from rusting. Our industrial society also uses zinc in brass, bronze, and other alloys; die casting; and tire manufacture. Applying the four basic steps above, we determine a global sustainable limiting rate of zinc consumption in Chart 1. Is the sustainable allocation of 1.5 kg of zinc per person per year calculated in Chart 1 sufficient for an average person’s technological and social requirements? Consider this question from the perspective of the use of materials in a common appliance, the automobile. Automobiles are one of the major technological goods that contain zinc in the form of galvanized steel chassis and body parts. The zinc content of an average car is 3-4% of the total weight of the automobile (25). Assuming that an average automobile weighs about 900 kg, the average automobile contains about 900 kg × 0.035 ) 32 kg of zinc. From a “zinc perspective”, the sustainable rate of automobile purchase is thus 32/1.5 ) 21 yr. Thus, an individual’s annual sustainable zinc allotment lets her or him buy a new car every 21 yr. For comparison, as shown in Figure 2, the average American car is only about 8 years old (26). Furthermore, if during those 21 yr an American citizen wants anything else containing zinc, like a brass doorknob or some galvanized fencing, the new car purchase cycle will be lengthened. An argument against this simple calculation would be that substitutes are widely available for galvanized steel (such as aluminum or composite materials not needing corrosion protection) that would reduce the need for mined or recycled zinc. Substitution raises a few important questions beyond whether a substitute is technologically feasible, such as, is
FIGURE 2. Comparison of the average age of today’s automobiles in the United States (20) and the average age of automobiles required to achieve sustainability from a zinc perspective. the substitute economically feasible? Is the substitute sustainable? Is the substitute of equal quality? Is the substitute socially (morally, ethically, etc.) acceptable? Will the substitute be accepted by consumers (due to aesthetics, “feel,” or style)? These questions range from the scientific to the political and social. For the case of aluminum or composite materials substituting for zinc-galvanized steel in automobile manufacture, all of these questions could be satisfactorily answered and soon may have to be. Answering these and other questions (such as how zinc reuse and recycling might be increased) will help policy-makers devise the necessary corrective actions and incentives to achieve sustainable zinc use. Example 2: Sustainable Supplies of Germanium. What happens when the material in question has no readily apparent substitute? One potential example of an apparently “unsubstitutable” industrial mineral is germanium, 75% of which is used in optical fiber systems, infrared optics, solar electrical applications, and other specialty glass uses. Germanium plays a key role in giving these glasses their desired optical properties. Its most common use is as a dopant in the cylindrical core of glass fibers, slightly increasing the refractive index of the core glass as compared to the cladding. Lightwaves impinging on the core-cladding interface are trapped inside the core and can transmit the light signal for distances up to 30-60 km (27). Germanium outperforms all currently known materials in these applications. Furthermore, germanium use will likely increase in the future as fiber optic cables continue to replace traditional copper wire and as solar-electric power becomes more widely available. VOL. 36, NO. 4, 2002 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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CHART 2. Calculation of a United States Sustainable Limiting Rate of Germanium Consumption
We compute a United States sustainable limiting rate of germanium consumption in Chart 2. Is the sustainable allocation of 36 mg of germanium per person per year calculated in Chart 2 sufficient for an average person’s technological and social requirements? Consider the following exploration of fiber optic cable replacing copper for U.S. telephone wire needs (as our society demands increased bandwidth and data transmission capabilities for the new information age). The composition of an average telecommunications fiber core is 5 mol % GeO2, 0.5 mol % P2O5, and 94.5 mol % SiO2 (28), which translates to approximately 8.4 wt % GeO2. A typical single mode optical fiber (with a 10-µm core and a fused silica density of 2.2 g/cm3) has roughly 14 mg of germanium/km of optical fiber. A typical telecommunications cable would contain 36 optical fibers (a cable with six fiber bundles, each bundle having six individual fibers), translating to 504 mg of germanium/km of fiber optic cable. Assuming that an average road has at least one telephone cable along its length, then replacing the copper telephone cable with optical fiber cable along the 3 830 000 km of paved roads in the United States (29) would require approximately 2 Mg of germanium. Dividing by the 260 million people in the United States, each person would have to contribute a one-time donation of about 8 mg to rewire the country. From a “germanium perspective”, replacing copper wire with fiber optic cable for telephone service in the streets of the United States would most likely be sustainable. Obviously, most countries of the world do not currently have the demand for fiber optic cable of the United States and other OECD countries. It would be very interesting to perform a similar analysis for constructing a new telecommunications network in a developing country. Such an analysis could begin a discussion on whether wiring the streets with fiber optic cable from the beginning, instead of copper wire, would be the more sustainable choice. Example 3: Sustainable Production of Greenhouse Gases. As stated above, two of the major Earth system conditions we wish to maintain are a Holocene-style climate and functioning planetary engineering systems (forests, wetlands, etc.). The sustainability of each is closely linked to rates and magnitudes of global climate change. Perhaps one sustainability threshold for climate change would be to limit human disruption of climate below that which significantly alters ocean circulation patterns, such as the North Atlantic 526
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thermohaline circulation. According to some climate change models (30), limiting the growing concentrations of atmospheric CO2 to a doubling of pre-industrial revolution concentrations (i.e., to about 550 ppmv) would most likely not permanently alter Atlantic Ocean circulation (although it could weaken significantly and take hundreds of years to recover). It would be easy to debate that a doubling of CO2 would still have some nonzero effects on maintaining climate conditions and ensuring the viability of ecosystem function. Yet doubling of atmospheric CO2 has emerged as a political target and a focal point for scientific analysis in most climate change models. Therefore, using the basic steps described above, in Chart 3 we calculate a global sustainable level of CO2 addition to the atmosphere, making the controversial assumption that CO2 doubling will be reasonably sustainable. Is a sustainable allocation of 1 metric ton (t) of carbon per person per year calculated in Chart 3 reasonable? Consider the following data on automobile usage and CO2 production (32). Driving an automobile produces approximately 62 g of carbon (in the form of CO2) per vehicle kilometer traveled. Drivers in the United States average 20 000 km/yr, which translates to 1.24 Mg of carbon produced/yr by driving. A driver would have to reduce his/her yearly driving by nearly 4000 km in order to achieve the 1 Mg of carbon per person sustainability goal. Even so, this would leave nothing for home heating, electricity for a computer, or a personal share in the larger industrial-technological systems that support the economy. Alternative energy sources, carbon sequestration possibilities, less-carbon-intensive production systems, personal driving habits, vehicle technology, public transportation systems, or some combination thereof must all be incorporated into the public discourse on climate change. However, as is the theme of this exercise, this public discourse would be well served by having a sustainable target toward which to aim. A similar approach can be taken to explore threats to sustainability caused by the cumulative leakage of poisons from human use cycles into susceptible ecosystems. Because ecosystems are unique, analyses of this sort would need to be performed at the regional or local level. The determination of leakage rates and the establishment of appropriate sustainability limits for individual ecosystems are likely to present substantial challenges, but the general approach appears straightforward.
CHART 3. Calculation of a Global Sustainable Limiting Rate of Carbon Dioxide Production
Discussion The examples above highlight the great gulf between our current technological lifestyle (especially in the developed world) and measurably sustainable human-industrial activity. These examples are admittedly somewhat shocking. Nonetheless, were sustainability goals such as these to be agreed upon, one could then address those goals through innovation and enlightened decision-making. For instance, highlighting the gap between current consumption rates and sustainable consumption rates could encourage government and industry to invest in “factor X” eco-efficiency programs (that is, programs that encourage reduced resource consumption by a factor of say 4, 10, or 50) (33, 34). Such stepwise improvement may be justified when the gaps between our present and a sustainable future are as wide as our preliminary measurements seem to indicate. However, these examples and the assumptions made herein raise a number of contentious issues, four of which we address below. The Simplicity vs Complexity Issue. Our analysis here is necessarily simplified, and the simple metrics we have developed do not yet handle the inherent complexity of our global environmental system. We also say little about the methods of production for any of these resources, which can involve enormous energy use, serious habitat disruption, environmental degradation, etc. For instance, even something seemingly positive such as increased zinc recycling to address sustainability issues may have negative effects on energy consumption and greenhouse gas production through transportation of recyclable material. Furthermore, the major uses of zinc are for coating steel and being alloyed with copper. Iron and copper cycles and their sustainability are thus linked to that of zinc. Whether the sustainability of one resource outweighs the unsustainability of the other two is cause for serious debate, and more in-depth analysis that is beyond the scope of the simple metrics outlined herein. We admit to “compartmentalizing of resource cycles” for the sake of easier analysis. There is a point at which complexity for complexity’s sake offers only marginal benefits however. Our calculations suggest that most of our current technological systems operate at 2× or more of the sustainable rate.
On the order of magnitude scale, even the simple sustainability measurements herein provide guidance toward reasonable targets to achieve more sustainable ends. The Property Rights Issue. In calculating preliminary values for sustainable rates of use of various resources on an individual basis, we have allocated resources in the simplest possible waysan equivalent amount to each human being. A variation on this approach is to allocate a tradable permit to each individual, thereby permitting portions of the sustainable use level to be traded in financial markets. Either choice is satisfactory from a global equity standpoint (although, in reality far from current social norms) but immediately raises potential legal issues surrounding property rights. Resources are not equally distributed on a geographical basis, and they are owned by a variety of entities including nations, corporations, and individuals. To allocate resources on a global basis is to dictate at least to whom those resources must be sold and doubtless to have at least some influence on price. Several alternative approaches, all problematic to varying degrees, are as follows: (i) The global total extraction rate could be dictated, but allocation left to market forces. (ii) Regional total extraction rates could be dictated, and residents of resource-rich regions could be allocated more of the local resource than nonresidents. (iii) Regional allocations could be based on both local virgin resources and local rates of recycling. In the first approach, new opportunities for trade are likely to emerge. However, regardless of what choice is adopted, sustainability from a resource standpoint requires the establishment of an upper extraction limit followed by some method for allocating each year’s virgin material supply. This would redefine current notions of private property by imposing limits on extraction and could transfer a portion of these property rights to the disenfranchised. These are questions of policy, politics, diplomacy, ethics, and law, in which our simple calculations can greatly inform sustainability debates that rage among the developed and the developing world, the rich and the poor, the large nations and the small islands, and the North and the South. VOL. 36, NO. 4, 2002 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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The Limits to Growth or Resource Scarcity Issue. Resource availability is only one part of the larger sustainability question and is a controversial one at that. Arguments for and against resource scarcity have been with us at least since The Limits to Growth first appeared in the early 1970s (35). A more recent article on mineral resources and environmental issues by Hodges (36) noted that, contrary to most predictions, persistent shortages of industrial minerals have not yet occurred. Clearly, clean technologies and economic incentives have acted both to increase resource availability and to improve the overall efficiency of resource use. However, environmental considerations and land use issues are becoming more important than scarcity issues. As less and less of the world remains unexplored, geologists are increasingly pointing out the eventual exhaustion of inexpensive supplies of nonrenewable resources (21). In addition to absolute abundance limitations, the history of adequate resource supply has occurred within a period of essentially unlimited and inexpensive energy together with a paucity of environmental regulations on mineral extraction and processing. As we move toward a transition from growing production to shrinking production of portable energy (e.g., petroleum) (37) as ore grades continue to decrease (38) and as environmental scrutiny of industrial operations increases, energy and environmental limitations to resource supply will become increasingly constraining. Resource scarcity is not a static issue; rather, it is a dynamic one. New technologies develop, populations increase, cultures evolve, and all of these changes influence resource consumption. A sustainable rate of use is thus a moving target rather than one fixed for all time. We thus recommend recomputing the targets every few years, while retaining the 50-yr depletion horizon. The result will be 2-fold: keeping targets up to date and maintaining modest levels of resources for the use of future generations. It may turn out that resource limitations will not be a major sustainability concern, but there are many reasons why they might be, and a conservative approach to sustainability would take resource limitations into account. The Substitution Issue. Whether or not one believes that resource scarcity is an issue to be concerned about may hinge on the belief that, regardless of scarcity, our technological society will find a new way to continue to develop. A standard argument made against the possibility of resource exhaustion is that scarcity drives prices up and thereby forces substitutes to emerge. This argument is obviously valid in some casess synthetic rubber, for example, or for the development of completely new technologies (e.g., transistors for vacuum tubes). It is obviously invalid, however, in several other cases. There is no substitute for water, for example, as Chinese living near the mouth of the Yellow River have discovered in the past decade (39). Similarly, there appears to be no substitute for materials whose physical or chemical properties uniquely serve a needsgermanium in fiber optic cables or thallium in superconductors, for example. One way to get a first estimate of substitution potential is to ask which uses of a material could remain if its price were to increase by 10 times. Thallium use in superconductors would probably continue because there are no obvious suitable substitutes and the willingness-to-pay for this novel technology is still very high. Petroleum use for petrochemicals might continue because in some applications (some plastics, for instance) there are currently no better or cheaper substitutes. Arguably, petroleum use for vehicle fuel probably might not continue at 10 times the price because alternative fuels could perhaps become competitive and attractive. Thus, cost per se is not a complete descriptor of sustainability and particularly not a descriptor of sustaining our present spectrum of materials uses. It is true that if prices increase by 10 times one can expect use to decrease and the material to remain available. 528
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However, sustainability (as generally conceived) is not about maintaining resource availability by lowering living standards; it is about maintaining resource availability while maintaining living standards. A further issue is the time required for suitable substitutes or new technologies to be developed and deployed. For small consumer products that time can be short; for key industrial processes that enable materials to be available at reasonable prices, it can take several decades (40). Relying on substitution or technological replacement to solve resource shortage problems thus involves three gambles: (i) that suitable substitutes can be developed; (ii) that the substitutes themselves do not come with their own untenable baggage of supply limitations, environmental harm, and high energy costs; and (iii) that the substitutes can be developed and deployed on the time scale needed. All of these gambles may be risky. To summarize, our central theme is that the word sustainable is being widely used to mean something like “a bit more environmentally responsible”. There are two problems with this. One is simple false advertising: there is the clear implication in these uses that sustainable activities have been undertaken in order to maintain or prolong a favorable environmental situation for our planet, when in fact no assessment has been made of the truth or falsity of the statements. The second is that an opportunity is being missed because sustainability assessments can indeed be made and the results used to encourage beneficial actions (such as encouraging government and industry to markedly increase energy and resource efficiency), although doing so raises a number of issues that need to be discussed and resolved. In Our Common Journey, the Board on Sustainable Development (10) emphasizes that the pathway to sustainability cannot be charted in advance. Technological and societal change is certain to influence any quantitative sustainability goals that we derive. This fact does not mean that such goals have no value. Rather, it means that we must revisit these goals at regular intervals, expecting to adjust them in light of new information on supplies, uses, or environmental stresses. We have sought in this paper to quantify the concept of sustainability where it seemed readily capable of quantification. We recognize that there are many potentially legitimate approaches to doing so and present examples more to stimulate thinking and debate than to suggest the correctness of our choices. It is clear that important ethical and legal issues emerge from this exercise and would emerge as well from attempts to establish sustainability in economics, in the equitable distribution of environmental benefits and burdens, and in many other areas. This obvious complexity should not be an excuse for delay however. If we are indeed serious about sustainability, and many people and organizations say that they are, we can move forward only by converting that fuzzy concept to dependable, measurable metrics. With this paper, we begin the discussion.
Acknowledgments This research was funded by the U.S. National Science Foundation under Grant BES-9818788. R.J.K. thanks the Environmental Research and Education Foundation for graduate student support. We thank Daniel Esty, Robert Frosch, Kai Lee, Sandra Postel, Gus Speth, E-an Zen, and Maria Zuber for helpful comments on earlier versions of this work.
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Received for review February 1, 2001. Revised manuscript received October 26, 2001. Accepted November 2, 2001. ES0106016
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