This introductory chapter sets the scene for the discussion in the edited volume on how new agricultural affects tropical forests. It critically reviews four hypotheses that have been central in the claim that better technologies help protect forests: the Borlaug, the subsistence, the economic development and the land degradation-deforestation hypotheses. Each of them appears to be valid only under certain restrictive conditions. The chapter then gives the aims and scope of the book, the key conclusions, as well as a summary of each of the chapters. A key objective of the book is to identify which technologies under which conditions lead to a win-win situation or trade-off between forest conservation and increasing farm productivity.