Suchergebnisse

The concepts of dynamic ecological equilibrium and optimal externality are defined. The former is frequently advanced by ecologists as an objective of environmental planning. The latter is advanced as a planning objective by economists of the cost—benefit school of thought. It is demonstrated that the two are necessarily incompatible objectives: the former precludes the latter, and vice versa. If the importance of ecological 'steady states' can be shown, however, it follows from the analysis that the ecological objective is logically prior to the economic objective. The conventional approach to planning for 'externality correction' is then misplaced.

Efforts to 'operationalize' a concept of sustainability into appraisal methods for practical decisionmaking have been few and generally unpersuasive. In this paper it is argued that this need not be the case if a set of environmentally compensating, or 'shadow', projects within an overall portfolio are used to ensure a sustainability objective of setting a constraint on the depletion and degradation of the stock of natural capital. This can be achieved through both a 'weak' and a 'strong' sustainability criterion. In both cases the resulting optimum differs from the efficient optimum of the conventional cost-benefit criterion, but the basic cost-benefit model remains intact.