This course deals with ecological principles of the conservation and use of biodiversity (plants and animals), at various spatial and temporal levels. The course introduces basic patterns of ecology and discusses the history of plant conservation, human use of biodiversity and the link between conservation and use. A specific focus is put on vegetation history, the history of domestication of food plants and the origins of agriculture. It discusses previous and current threats to plant diversity in a wider landscape context, giving examples of traditional cultural landscapes in Europe. In addition, examples are given of highly diverse agro-ecological systems worldwide, possibilities to increase levels of biodiversity and to diversify agricultural systems.