ABSTRACT
Cities are part of the natural environment and dependent on it for basic resources including food, water, and raw materials for manufacturing. Over thousands of years, the growth of cities has created complex networks of exchange that have enabled cities to obtain goods not locally available, and cities are quite dependent on these networks for their very existence. All cities are based on an agricultural economy for food, but trade networks have grown so complex that an urban consumer often has no idea from where their food comes and the social or environmental impact of their choices in other places.
The trade that supports cities is more than food: cities produce an array of goods and services that enables them to trade for basic resources from other places. This production often has such side effects such as pollution and carbon emissions. In addition, the growth of new neighborhoods in the metropolitan area often alters the local ecosystem, and the agriculture required to feed cities results in more land brought under cultivation with a loss of biodiversity in rural areas.
