Abstract
The purpose of this article is to examine the consequences of using the environmental variable (in its manifold appearances) to describe the dynamics of economic systems. The focus is on the ability of economic growth to guarantee sustainable use of environmental resources. A dynamic optimization technique is used as the standard theory of optimal control. Everybody knows that economists have used, and often still use, the terms economic growth and economic development in the same way. The analysis of the models proposed here is based, firstly, on the following distinction as a basic convention between two concepts: economic growth and economic development. This convention gives us a better view of the different weight that the environment takes on with respect to the economic dynamic and how this in turn influences the architecture of models. Both hypotheses and the results depend on the specific perspective from which authors have analyzed the problem. In a first case the focus is on a concept of economic progress in which collective wellbeing is directly linked to increases in income, that is to the quantity of goods (for consumption and investment) available to agents (consumers and enterprises) following growth in productivity: a case of sustainable economic growth, it means the possibility that wealth (and hence consumption) is able to increase steadily over time. Sustainable development, on the other hand, means the whole range of structural, economic, social and institutional changes accompanying growth. A case of economic progress it could be seen as a synonymous for a better quality of life, that is not only as growth in GNP: it does involve growth in income, but what is more important are often non-economic variables like the environment governance which generate services and functions contributing directly and indirectly to individual and collective wellbeing, as well as supplying the factors necessary to support productivity. In this way sustainability becomes synonymous of an economic process which does not change the basic functions of ecosystems. Sustainable development means an increase over time of a better quality of life. The environment, in all aspects, must (and can) ‘support’ this notion of the economic system, enabling it to live and grow. The conventional distinction between growth and development leads to different approaches of which we analyse some details. To conclude, the debate on sustainability allows one to compare different ethical principles. Eco-economists claim that the emphasis must be placed on the system's needs, rather than individual ones. This implies an ethical judgment on the role and rights of individuals living today as regards survival of the system and future generations' welfare. Moreover, given that individual behaviour is driven by egoistic motivations, supporters of sustainability examine how such behaviour can be modified and how such modifications can be achieved. Generally speaking quality and wealth should not trade off but an ‘open approach’ is required also adopting self-sustainability cathegory.