This paper outlines the concept of environmental sustainability (ES), shows why it is important to make it a top-priority goal, and why that will be difficult to attain but essential. The ES equation of impact = population x affluence x technology, is outlined. When the world approaches stability in both population size and the throughput of energy and materials per unit of production, we may indeed be approaching sustainability. As the world's population is apt to double every 40 years, and as only a few countries (e.g. Japan and Sweden) have managed so far to reduce the energy intensity or production, we are hurtling away from sustainability rather than even approaching it, Environmental sustainability can be approached by implementing four priorities: first, by using sound microeconomic means; second, by using sound macroeconomics to differentiate between use and liquidation of natural capital by means of environmental accounting; third, by using environmental assessment to incorporate environmental costs into project appraisal; and fourth - until the first three become fully achieved - by following operational guidelines for sustainability. Thus: 1) Sound Microeconomic Aleans involve: (1) Getting the prices right: to reflect full social marginal opportunity cost; use the 'full cost' principle, or the 'cradle-to-grave' approach. (2) Repealing perverse fiscal incentives. (3) Strengthening the 'polluter pays' principles. (4) Including non-monetary values in project justification- (5) Adopting the transparency principle that markets can function efficiently only if relevant information is available at low cost. This involves the participation of people in decisions affecting them, and advertising who is polluting what and by how much. 2) Sound Macroeconomics by Environmental Accounting is essential to discern decapitalization and to shift to using income rather than drawing down capital assets. Environmental accounting clarifies what is liquidation of natural capital from what is income. This is essential because decapitalization is frequently confused as income. Environmental accounting warns us when liquidation of potentially renewable resources exceeds their regeneration rates, such as in many forests. 3) Environmental Assessment is part of the project selection process. The purpose of EA is to ensure that the development options under consideration are environmentally sustainable. Any environmental consequences should be addressed in project selection, planning, siting, and design. EAs identify ways of preventing, minimizing, mitigating, or compensating for, adverse impacts. 4) Sustainability Guidelines: Until the first three rules are heeded and duly acted on, the following guidelines will be necessary: 1, Output Rule: - waste emissions from a project should be within the assimilative capacity of the local environment to absorb without unacceptable degradation of its future waste-absorptive capacity; and 2, Input Guide: - harvest rates or renewable resource inputs should be within regenerative capacity of the natural system that generates them. Depletion rates of non-renewable resource inputs should not exceed the rate at which renewable substitutes are developed by human invention and investment.
