With over half the global population already living in urban environments and an additional 1.3 million rural migrants joining them every week, we are seeing a fundamental shift in the core relationship of human society: that between city and country. Cities have always relied on the countryside for their sustenance, but in the past so few people lived in them (just three percent in 1800) that their ecological impact was limited. Today, the opposite is true. And if the future is truly urban, we urgently need to redefine what that means.

Of all the resources needed to sustain a city, none is more vital than food. Before industrialisation this was more obvious: the physical difficulty of producing and transporting food made its supply the dominant priority of every urban authority. No city was ever built without first considering where its food was to come from, and perishable foods, such as fruit and vegetables, were grown as locally as possible, most often in the city fringes. Fresh foods, including meat and fish, had to be consumed seasonally, with the excess preserved for winter by salting, drying or pickling. No food was ever wasted: leftover scraps were fed to pigs and chickens, and human and animal waste was collected and spread as fertiliser. The sights and smells of food - from unripe to ripe, raw to cooked, fresh to rotten - were omnipresent.

In the post-industrial era, however, things are very different. Today few of us witness the effort it takes to feed us, because industrialisation has hidden it from view. Railways in the 19th century emancipated cities from geography, making it possible to build them any size, any shape, any place. As cities sprawled, food systems industrialised in order to feed them, and, for the first time in history, the two grew apart. While architects and planners dreamed of building cities free from mess and smell, nascent agribusinesses strove for ever-greater 'efficiencies' in the food chain in order to maximise the vast profits to be made from supplying them with food. As a result, food production was increasingly located, not in or close to cities, but thousands of miles away, in places where natural resources and cheap labour could be most readily exploited.