This special issue is concerned with environmental Kuznets curves (EKC) - the hypothesis that there is an ‘inverted-U’ relationship between various indicators of environmental degradation and levels of per capita income. Explanations as to why environmental degradation should first increase then decline with income have focused on a number of underlying relationships, including: the effects of structural economic change on the use of the environment for resource inputs and to assimilate waste; the link between the demand for environmental quality and income; types of environmental degradation and ecological processes.