In 2005 over 40 % of the Earth’s land was given over to agriculture. This is an area of roughly 4.6 billion hectares, about the size of South America. A further 3.2 to 3.6 billion hectares is being used to raise livestock. By 2050 up to 80% of the earth’s population will live in urban centres. If food is to be produced and consumed in the same inefficient way as is today, we will need further arable farm land the size of Brazil to support this population.