Welcome to environmental economics, the study of why and how we befoul our environment and how, with some practical interventions, we can do better by it and by ourselves. Popular awareness of the importance of the subject grows by the day, as scarcely a day goes by without some report of a new or old environmental problem or a new or old idea for a policy appearing in some corner of the press.

Since the subject is a branch of economics, and economic theory forms the basis for this approach to the study of how we humans interact with our environment, I kick off the text with a refresher on some economic basics—models that will be used throughout the chapters of the text. Some of the exposition is expressed in equations that I have kept in the text as parts of sentences to emphasize that they can be read just like sentences—because they are sentences. I explain the equations in detail, but writing only in words what the equations can convey much more compactly in symbols can get more tedious for readers than the equations may seem, even for readers initially uncomfortable with the mathematical format.