At the start of the new millennium we live in a world of unprecedented human numbers. There are currently about 6.3 billion people, and this figure is expected to increase to some nine billion by 2050. About half of the world’s population live in cities, a figure which is likely to grow to two thirds by 2030. Most cities are being built on farmland, a factor that will certainly reduce the world’s food production capacity unless city people produce significant proportions of their own food. So some important questions need to be answered: can the global environment cope with this ‘age of the city’? Will there be any untouched natural systems left? How can the world’s growing numbers of city people be fed?
A very useful methodology in this context is to measure the ‘ecological footprint’ of cities, drawing on the work of Canadian ecologist William Rees and his Swiss colleague Mathis Wackernagel. As they see it, we need to quantify the land areas required to supply cities with essential resource services – the footprints of cities. These consists of three main components – the surface areas required:
1. to feed cities;
2. to supply them with forest products; and
3. to reabsorb their waste, and particularly their carbon dioxide output.
Using this method, I have tried to assess the ecological footprint of the city where I live, London, which has a population of just over seven million.
I found that it extends to around 125 times its own surface area of 160 000 ha, a total of 20 million ha. This breaks down as follows: London requires about 1.2 hectares of farmland per person, a total of 8.4 million hectares, or around 40 times its surface area. The forest area needed to supply it timber and paper is about 768 000 ha. The area that would be required to sequester its annual output of about 60 million tonnes of CO2 is by far the largest – about ten million ha, or half the total footprint.
A key issue here is how worldwide urbanisation and growth in affluence will increase human demands for land surfaces. It has been estimated that if developing countries copy our Western urban lifestyles – in terms of demands for food, forest products and energy – we will need three planets, rather than the one that we actually have. It is of crucial importance, therefore, for cities in developed countries to become much more efficient in the way they use resources, and that certainly includes their food supply. Urban agriculture can make a crucial contribution here.
But here we are primarily concerned with the land area required to feed large cities such as London, and the fact that food now tends to come from further and further afield.
London, of course, was the world’s pioneering mega-city. It grew from just under a million people in 1800 to about 8.5 million in 1939, a city of an unprecedented size. At first London drew on a largely local food supply. But new transport technologies made it possible to bring its food in from further and further away. Steam ships supplied grain from Canada and the USA, lamb from New Zealand, wine from France and Italy, oranges from Spain and Brazil, bananas from the West Indies and South America. Today food is brought to us from just about anywhere – no longer just in freighters and trucks, but also in aeroplanes flying in from half way across the world.