Michael Calver

Science is both highly competitive and highly cooperative, so a rigorous evaluation of an idea comes not from one's close colleagues, but from one's opponents (Hull 1988). While robust disagreement may not lead to consensus, at its best it should lead to clarification of areas of agreement and areas of dispute, as well as dialogue on the empirical tests necessary to solve the disagreements. In this context, David Theodoropoulos' new book on invasion biology attempts a rigorous, sceptical critique of the belief that invasive species are a significant threat to biodiversity.