This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book describes global approach and integrates as many scientific fields as necessary to better understand how biodiversity is organised in space and time and how it is influenced by climatic and environmental variability, as well as global change. It explores the potential effects of global change including anthropogenic climate change and ocean acidification, on marine biodiversity. The book also explores the relationships between biodiversity and ecosystem functioning at all spatial and temporal scales, including the geological timescale. It examines the debate on the role of biodiversity for ecosystem functioning. The book also examines the effects of hydro-climatic and environmental changes on marine biodiversity. It highlights that people urgently need to adopt a macroscopic approach, based on joint global monitoring programmes to better understand the effects of global change on marine biodiversity.