The state of ecosystems, biological communities and species are continuously changing as a result of both natural processes and the activities of humans. In order to detect and understand these changes, effective ecological monitoring programmes are required. This book offers an introduction to the topic and provides both a rationale for monitoring and a practical guide to the techniques available. Written in a nontechnical style, the book covers the relevance and growth of ecological monitoring, the organizations and programmes involved, the science of ecological monitoring and an assessment of methods in practice, including many examples from monitoring programmes around the world.