Population et environnement : des liaisons incertaines

Population and environment: uncertain connections

Économiste, CIRED, Jardin tropical, 45 bis avenue de la Belle Gabrielle, 94736 Nogent-sur-Marne, France

Résumé

Un traitement théorique cohérent du lien entre dynamique démographique et changement environnemental montre que cette relation demeure incertaine. Bien que l'on ait souvent mis l'accent sur la relation négative et significative entre ces deux variables depuis la fin des années 1970, plusieurs difficultés économétriques suggèrent qu'il puisse s'agir d'un artefact statistique. Les difficultés d'une validation empirique incontestable de la relation entre croissance démographique et croissance économique créent ainsi une situation de controverse, où il est difficile de quantifier les liens entre les déterminants du changement environnemental, et donc de trancher en toute rigueur sur le choix d'un modèle théorique plutôt que sur un autre.

Abstract

A consistent theoretical assessment of the links between demographic and environmental dynamics shows that these links remain uncertain. Two opposite paradigms can put forward in this debate. A first paradigm considers that technical change is exogenous to the economic system. Due to decreasing outputs, the capital dilution effect and negative externalities on the environment, rapid demographic growth has a negative effect on both economic growth and the environment. On the other hand, the second paradigm assumes that, in the long term, economic growth is stimulated by population growth, thus inducing an improvement in environmentally friendly technologies, in conformity with the growth models based on endogenous technical change. Although, emphasis has often been put since the late 1970s on the negative and significant link between these two variables, several econometric difficulties suggest that this may prove to be a statistical artifact. The difficulties of an irrefutable empirical validation of the link between demographic and economic growths create a situation of controversy which make it difficult to quantify the relation between the determinants of environmental change and therefore to rigorously select one out of several theoretical models.