Starting from a definition of risk governance, the paper examines a number of environmental contingencies and crises where traditional risk assessments based on expert calculations and computer models proved inadequate. While the growing inclusion of uncertainty in scientific descriptions and forecasts is recognized, the tendency to express it in probabilistic terms is criticized because it fails to account for the complexity of natural phenomena and their interactions with human actions. The paper argues that contributions from different disciplines and other types of knowledge need to be integrated for improving disaster prevention and response. This implies a redefinition of the role of science in society as well as a general change of attitude, revisiting Descartes’ idea of humans as “masters and possessors of nature”.