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WHAT IS TO BE SUSTAINED?

Sustainability means different things to different people. In fact, some would argue that the concept’s appeal derives from its vagueness. Nevertheless, most definitions fall into one or a combination of two categories. The first emphasizes the sustainability of physical resources. Sustainability of a single renewable resource, such as a forest or fishery, requires that the rate of harvest or use not exceed the rate of natural growth or regeneration. An annual timber harvest of one million cubic meters, for example, is sustainable as long as the annual rate of forest growth is at least one million cubic meters. Sustainability also applies to sets of physical resources, such as an ecosystem containing trees, fish, wildlife, soil, and water. This genre of definitions cannot be applied sensu strictu to mineral deposits, which in terms of human life spans are non-renewable.

The second category emphasizes sustainability in a socio-economic sense—that is, sustainability of human living standards. Sustainability in this sense does not refer to a single resource, such as copper or oil, or to a set of natural resources, such as an ecosystem; rather it refers to the well being of society as a whole. Defining and measuring exactly what is to be sustained in this socio-economic sense is fraught with difficulty and disagreement. A purely economic approach requires only that the overall stock of capital, or inputs to the production of goods and services, remain at least constant from one generation to another; the capacity to generate income, in other words, remains at least the same over time. Stated more generally in the words of Nobel laureate Robert Solow, “a sustainable path is one that allows every future generation the option of being as well off as its



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MINERAL RESOURCES AND SUSTAINABILITY: CHALLENGES FOR EARTH SCIENTISTS 2 WHAT IS TO BE SUSTAINED? Sustainability means different things to different people. In fact, some would argue that the concept’s appeal derives from its vagueness. Nevertheless, most definitions fall into one or a combination of two categories. The first emphasizes the sustainability of physical resources. Sustainability of a single renewable resource, such as a forest or fishery, requires that the rate of harvest or use not exceed the rate of natural growth or regeneration. An annual timber harvest of one million cubic meters, for example, is sustainable as long as the annual rate of forest growth is at least one million cubic meters. Sustainability also applies to sets of physical resources, such as an ecosystem containing trees, fish, wildlife, soil, and water. This genre of definitions cannot be applied sensu strictu to mineral deposits, which in terms of human life spans are non-renewable. The second category emphasizes sustainability in a socio-economic sense—that is, sustainability of human living standards. Sustainability in this sense does not refer to a single resource, such as copper or oil, or to a set of natural resources, such as an ecosystem; rather it refers to the well being of society as a whole. Defining and measuring exactly what is to be sustained in this socio-economic sense is fraught with difficulty and disagreement. A purely economic approach requires only that the overall stock of capital, or inputs to the production of goods and services, remain at least constant from one generation to another; the capacity to generate income, in other words, remains at least the same over time. Stated more generally in the words of Nobel laureate Robert Solow, “a sustainable path is one that allows every future generation the option of being as well off as its

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MINERAL RESOURCES AND SUSTAINABILITY: CHALLENGES FOR EARTH SCIENTISTS predecessors” (Solow, 1993). This is essentially the same as the Brundtland definition. The economic approach permits substitution between natural and man-made capital. Natural capital includes nonrenewable resources, such as energy fuels and minerals, and renewable resources, such as air, land, water, forests, and fish. Man-made capital includes human capital, the skills embodied in people, and physical capital, such as buildings, machinery, and production equipment. Activities that deplete the stock of natural capital are permitted as long as compensating investments are made to increase the stock of physical or human capital, leaving the overall capital stock intact. In other words, activities that deplete renewable resources or exhaust nonrenewable resources are consistent with sustainability as long as an appropriate portion of the proceeds of these activities is invested in reproducible, man-made resources such as education and technology. However, investing proceeds in man-made activities cannot be substituted for adequate environmental protection measures. Other approaches to sustainability are more restrictive. Some, sensing severe limits to potential substitutability, require that both the overall capital stock and the stock of natural resources remain at least constant. The extent of allowable substitution between natural and man-made resources is more limited. Still other approaches place greater emphasis on the sociological aspects of socioeconomic sustainability. 1 Exactly how, or whether, sustainability will come to be defined is not clear. What is clear, however, is that sustainability has led to heightened concern about both depletion of nonrenewable resources and degradation of the environment, including degradation 1   For more extensive introductions to sustainability and sustainable development, see Dixon and Fallon, 1989; Darmstadter, 1992; World Bank, 1992; Pearce and Warford, 1993; and Serageldin and Steer, 1994.)

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MINERAL RESOURCES AND SUSTAINABILITY: CHALLENGES FOR EARTH SCIENTISTS caused by mining. In each of these two areas, sustainability challenges earth scientists to redirect their scientific research, to assemble data that are usable in policy analysis and decision making, and ultimately to transmit their findings more clearly to policymakers and the public. It is to these challenges that the report now turns.

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