introduction of irrigation systems, constitute one of the principal sources of climate change and the loss of biodiversity. Many of these changes are related to the production of food for human consumption. By comparing systems that vary along a continuum from extensive to intensive patterns of land use, it is possible to elucidate the social driving forces leading to change in patterns of land use. This leads directly to a consideration of sustainability treated as the maintenance of the biogeochemical condition of soils and vegetation coupled with reliable crop production for users over the long-term.

2c: Valuing Consequences of Environmental Change. What alternative approaches are available for use in valuing consequences of environmental changes not well reflected in market prices? What institutional arrangements would we need to establish to ensure the effective use of the most promising of these approaches? Many of the large-scale consequences of anthropogenic changes in environmental systems are subject to a high degree of uncertainty, occur over long time periods (sometimes involving several human generations), and involve values that are not captured in a clear-cut way in market prices. Consequently, societies lack unambiguous indicators of the social costs and benefits of many global environmental changes. The long-term health effects of increased ultraviolet radiation illustrate the problems of measuring intertemporal distributions of benefits and costs. Biological diversity constitutes an example of nonmarketed resources under threat of serious degradation. Loss of geopolitical position resulting from unfavorable impacts of climate change on agricultural productivity exemplifies another class of nonmarket effects. Research on methods of valuing these kinds of consequences—especially methods capable of producing at least ordinal rankings—could yield high returns measured in terms of improving the quality of public discussion of appropriate ways of responding to global environmental changes. Valuation research should explicitly address the subjective nature of valuation and the phenomenon of differences in valuation, for instance, by exploring ways of soliciting valuations from different actors as part of the social decision process.

2d: Technology-Environment Relationship. What determines whether technologies developed and adopted in industry, agriculture, and other economic sectors mitigate or exacerbate global environmental change? What are the roles of factor prices, regulatory practices, systems of property rights, standards of performance, and other characteristics of the decision environment in



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