When we talk about environmental issues, we are usually talking about the ways human beings interact with and impact upon natural systems. This interaction takes place through a number of technologies, such as mining, agricultural and industrial technologies. As environmentalists, we pay close attention to how these technologies are designed and deployed and we advocate ways to minimize human impacts on nature. One very important technology mediating our relationship with nature and one that is sometimes overlooked is the city or town. Human settlements are the largest, most complicated technology ever created by human beings.
Urban areas are, therefore, where environmental problems are most severe.
Because this is where most products and services are produced and consumed, this is where most industrial pollution and wastes are created. Because most cars and other vehicles are owned and used by urban dwellers, this is where a large part of the air pollutants and greenhouse gases originate. The way cities grow and function has a huge impact on local, regional and global ecosystems. Without addressing urban environmental issues, we cannot hope to achieve sustainability on a global level. No human settlement can be sustainable in the strong sense of the word, if by that one means that they are self-reliant in terms of materials, use only renewable energy sources, and use only the absorptive capacity of local ecosystems.