Clearing land for pasture and feed crops has led to widespread deforestation and biodiversity loss and overgrazing leads to erosion and compaction. Furthermore, livestock production accounts for large amounts of water use and constitutes a source of water pollution from hormone use and other chemicals, as well as from the inadequate handling of manure. A limited number of genetically modified animals, animal substances, tissues and micro-organisms have been introduced in the production of livestock and fish to date.