توسعه اقتصادی و کیفیت محیط زیست: ارزیابی مجدد با توجه به ظرفیت خود بازسازی طبیعت

We study the relationship between economic development and consumption of natural resources using a vintage capital model. Consumption of natural resources is assumed to generate pollution, part of which will be absorbed by nature's self-regeneration capacity. We find that during the transition dynamics, the shape of the pollution output relationship will depend on the parameter determining nature's self-regeneration capacity. Using footprint and biological capacity data, we show empirically in a repeated cross-section of countries that the shape of the pollution–output relationship indeed depends on countries' capacity to regenerate part of the resources they consume from nature.

In October 2006 several newspapers announced that the earth had reached its ecological debt day/overshoot day. 1 This concept, which was first suggested by the Global Footprint Network (www.footprintnetwork.org) refers to the day in a year when humanity has consumed what nature can renew. In other words, if more wood is consumed than trees grow back, or fishery resources are depleted faster than spawn, then humanity has to dip into its stocks of natural capital. It is arguably then the tradeoff between the depletion of resources and the ability to regenerate these that is at the heart of the sustainability of countries' consumption habits. In other words, countries should be assessed not only in terms of the extent of pollution of the environment, but also with regard to their contribution in terms of rebuilding natural capital. This could then, for instance, be used to more accurately separate net debtors to the environment from net creditors, and hence allocate polluting rights accordingly. 2 Unfortunately academic studies generally have tended to disregard nature's regenerating ability when it comes to taking account of a country's contribution to polluting the environment, in part due to data availability. This is obvious, for instance, in the numerous studies that have tried to relate economic development to environmental pollution in what has come to be known as the Environmental Kuznets Curve (EKC), where pollution is often proxied by emissions of a particular pollutant, such as carbon dioxide or sulfur. In contrast, the recent footprint approach,3 has not only taken important steps to synthesizing many measures of environmental degradation into a single proxy, but also managed to net out a country's ability to regenerate nature (which is usually referred to as biological capacity or biocapacity).

In this study, we have theoretically derived an Environmental Kuznets Curve (EKC) using a vintage capital model, and explicitly taking account of the fact that environmental quality is not just an inverse measure of pollution. Our model contributes in several ways to the existing literature. First, we show that a bell-shaped relationship between environmental degradation and income per capita may appear once the optimal scrapping age has been reached. Furthermore, we show that neglecting nature's regeneration capacity has substantial implications on the shape of the relationship during the transition dynamics. In particular, before reaching the optimal scrapping age, the convergence speed will be higher and thus, the potential maximum of the EKC will be reached for lower values of income per capita.