Most natural populations intermittently experience extremely stressful conditions. This book discusses how such conditions can cause periods of intense selection, increasing both phenotypic and genetic variation, and allowing organisms with novel characteristics to be first generated and then established in the population. The authors argue that stressful conditions can have a major impact on the environment, backing up their arguments with evidence from the fossil record. They suggest further that, as a consequence, periods of stress must be taken into consideration when long term conservation strategies are planned, particularly as stressful conditions are becoming increasingly prevalent as a result of human activities. This broad overview will be of great interest to students and researchers in the field of evolutionary biology, genetics, ecology, palaeontology and conservation biology.