Statistical measures of unsustainability

Statistical measures are needed to reveal at a glance how far (or near) various countries are to meeting the conditions of long-run sustainability, and how conditions are changing on a year-to-year basis (i.e., whether sustainability is being approached or not). The scheme proposed in this paper presents numerical comparisons of energy and materials use in the real world vis a vis an ideal case where all of the identifiable criteria for sustainability are satisfied. Apart from population stabilization, five general but quantifiable criteria for sustainability are suggested, including (1) stabilization of greenhouse gas concentrations in the atmosphere, (2) stabilization of acidity (pH) in rainfall, (3) reduction of dissipative uses, and wastes, of heavy metals to natural mobilization rates, or lower, (4) elimination of agriculture based on pumping ''fossil'' water from non-renewable aquifers and (5) elimination of loss of arable land because of salination or erosion. Other criteria, such as preservation of biodiversity and socio-economic equity between countries and generations might be added to the list. They introduce more difficult measurement problems, however, which are not considered further in the paper. Having fixed the list of criteria, the next step is to identify measures that either go to zero or unity, as the system approaches more and more closely to sustainability, at least in the limited sense defined above. Various types of measures of sustainability/unsustainability can be developed, viz. (i) measures of relative dependence of the economy on non-renewable sources of energy and materials, (ii) measures of the productivity of energy and materials consumed by the economic system and (iii) measures of dissipative loss, especially of toxic and hazardous substances. Specific examples of each type are discussed.