This is a book by people who have had to make decisions which affect the environment in which we all live, decisions which sometimes affect the quality of life of millions. It is not an academic disquisition on how to approach decision-making. Most of the chapters are written by scientists who have had to take action or make recommendations on environmental matters in situations where the data are incomplete or choices hedged by factors beyond scientific resolution; the result is that they have had to resolve dilemmas about the proper way forward in the matter. My brief to the authors was to...