The site of Heathrow airport used to be London’s market garden. Its sandy soil is very suitable for vegetable growing. Today, even though it is largely concreted over, Heathrow is still London’s major food supplier, but in a rather different way: food is flown in from across the globe. Such a global har­vest offers us great culinary variety, but it requires the availability of vast quantities of fossil fuels. By the time food that has been air freighted for thou­sands of miles reaches a London dining room table, it will have used hundreds of times as much energy as the calories it actually contains. But it is not only air freighted food that is tremendously energy inten­sive. Frozen fish from the Atlantic contain some 100 times more energy than their calorific value, meat from UK farms 50 times more. These are astonish­ing figures. It seems unlikely that we can sustain such a high-energy food urban system for long.

But it is not only the energy input into our food system that should concern us, but also its impact on global land use. Increased demand for meat, in particular, has become a primary cause of defor­estation in virgin forests in the Amazon, Thailand, Malaysia and Indonesia. Animal feeds such as soy­beans and manioc produced in these places have been used extensively in Europe and Japan for many years. Now, economic and urban growth in large developing countries such as China is caus­ing a rapid increase in meat consumption there, and so increasing demand for soybeans from rain­forest and savannah regions elsewhere. In Brazil, this process started in Mato Grosso on the southern edge of the Amazon. Massive new road building programmes are now under way in the Amazon itself, which will result in the conversion of ever-larger areas of virgin forest into soybean fields to supply the growing demand for soybean from China’s cities.

Over the last 50 years, agriculture in developed countries across the world has been transformed into an ever more capital intensive, machine depend­ent system. In the UK, only one and a half per cent of the population is still producing food. Rural land­scapes here no longer exists in their own right but for the sole purpose of supplying urban demands.


Another important issue to be addressed is that, worldwide, we are seeing uni-directional food and therefore nutrient flows, from the country to the city, never to be returned to the land. This unsustainable system was pioneered in Rome 2000 years ago with the construction of the ‘cloaca maxima’through which much of the city’s sewage was flushed into the Mediterranean. More recently, in the 1850s, London, faced with major outbreaks of typhoid and cholera due to sewage pollution of the Thames, decided to separate its people from their sewage output. After much deliberation, London’s authori­ties took the decision not to recycle the sewage, but to dump it in the sea instead. From 1858 – the year of the ‘great stink’ – onwards a huge investment in a sewage disposal system was made. But because most of the sewage was now flushed away rather than used as fertiliser, it became necessary to keep the farmland feeding London productive by artificial means. The age of artificial fertilisers and chemical farming had begun.

A few years ago, flying from Rio de Janeiro to Sao Paulo I observed Rio’s vast, brown sewage ‘plume’ oozing out into the sea. Similar images can be seen at coastal cities all over the world. This one­way traffic of nutrients – from farmland, via cities into the sea – is causing havoc to coastal waters across the planet. These plumes contain the nitro­gen, potash and phosphate that should be used for growing the crops we eat. In addition, a substantial proportion of the artificial fertilisers now used on the world’s farms also ends up polluting rivers and coastal waters. If we are to create sustainable cities, we need to look at the nutrient flows between cities and the countryside, and at the ‘metabolism’ of our cities.