Agriculture: land use, food systems and biodiversity.

Agriculture has been extremely positive for humankind, but the environment has not necessarily fared so well. Dramatic changes in land use, water systems and, in more modern times, the large-scale use of artificial fertilizers and pesticides do not always have a positive impact on the natural world and its ecosystems: agriculture contributes to greenhouse gas emissions, water stress, soil degradation and biodiversity loss. This chapter first reviews the scale of land conversion and land use change over the course of history. It then examines the impact of agriculture on water resources, of livestock on greenhouse gas emission, of land use on biodiversity and on ecosystem services (e.g. forest cover), and of monoculture (a situation where a single, often human-adapted crop, is grown over a large area) on dietary diversity.