Sustainable development must satisfy the needs of present generations without compromising the ability of future generations to meet theirs. Although it looks at the economic, environmental and social aspects of sustainability, this article focuses specifically on an analysis of the concept in conjunction with the use and protection of natural resources. It shows how taking account of environmental goods, including the finite nature of certain natural resources, can change the way economists deal with the issues of growth, development and equity between generations. In this context, after a brief historical perspective on the concept of development, the paper shows how the potential for substitutability between natural and manufactured capital, for example in production technologies, lead to two paradigms, that of weak sustainability and that of strong sustainability. These two approaches are presented in an effort to explain how their merits can be mutually reinforcing.

The adoption of a common central Bank has modified the strategic relationships between fiscal and monetary authorities and raised in a new context the issue of debt stabilization. To study this problem, Van Aarle et al (1997) have proposed a two-country model with a common central bank. In a sense they obtained a neutrality result: the adoption of a common central bank does not modify the evolution of debt if the authorities can commit. This note reexamines this neutrality result by departing from the previous authors on three points: i) externalities are introduced between countries to account for the elasticity of the world interest rate to macro-economic policies, ii) the model features n countries, some of them remaining outside the monetary Union, iii) analytical results are given (many results of Van Aarle et al (1997) were numeric). In this extended context the neutrality result collapses: i) the institutional change introduces an asymmetry between countries, ii) countries inside the monetary union improve their long run welfare, iii) but the outside countries can win or lose under the new institutional setting. JEL Classification: C73, D92, L16.

Faut-il s’inquiéter de l’érosion de la biodiversité ? Que peut-on y faire ? Un ensemble de travaux menés au sein de l’UMR LAMETA présentent la biodiversité comme une notion singulièrement complexe, dont la valeur ne se révèle correctement sur aucun marché. Les estimations partielles qu’on peut en faire par d’autres moyens montrent néanmoins son importance, mais sa protection n’est pas chose aisée. Parce que la biodiversité concerne largement des domaines privés, et aussi des Etats souverains pour lesquels la protection de la nature n’est pas (encore) une priorité, les approches règlementaires sont d’un secours limité. Il faut s’efforcer de mieux comprendre les forces sociales qui compromettent la biodiversité, et utiliser ces mêmes forces pour la préserver.

Should we worry about the erosion of biodiversity? What can be done? Several studies carried out within the joint research unit LAMETA present biodiversity as a rather complex notion, the value of which does not accurately appear on any market. However, the partial assessments that can be made through other means show its importance, but its preservation is no easy thing. Since biodiversity greatly concerns private properties and also sovereign States for which the protection of the nature is not (yet) a priority, the statutory approaches are of limited help. We must try to gain a better understanding of the social forces that compromise biodiversity and use these same forces to preserve it.