This article offers an account of the economics of the environment. I sketch the subject's motivation and scope, and try to identify what we know and what we don't as yet know about matters of concern. This demands brazen selection, and I haven't avoided it: for the most part, the article explores the interface of rural poverty and the environmental resource-base in poor countries. A contrast is drawn between geographically localized resources and the global commons. The role of property rights, both private and collective, and their implied resource allocation mechanisms are studied. Criteria for social cost-benefit analysis of projects and policies are derived, and their link with the concept of net national product is drawn.