For several years there has been a growing interest in understanding the dynamics of parasites in ecosystems, as well as the diversity of ways in which they influence ecosystem functioning through their effects on host populations and communities. Ecologists, epidemiologists, evolutionary biologists, and other scientists are increasingly coming to realise that parasites must be taken into account when studying ecosystems. Parasitism and Ecosystems summarizes current knowledge on this topic, providing a comprehensive overview for researchers and students. It represents the first synthesis of both the roles and the consequences of pathogens in ecosystems, utilizing well-documented case-studies to illustrate the main issues as well as identifying prospects for future research.