Urban sustainability - ecological footprints

With over 50% of the world's population living in cities, creating or making cities sustainable is crucial to the whole sustainability agenda- making human activities tolerable, fair and viable, while reducing our contribution to climate change. An ecological footprint is a way of conceptualizing the processes that contribute to sustainability as shown in the context of the city below, an ecological footprint in a city is the result of inputs, outputs and internal actions. I purposely missed out some actions and outputs, can you think of any more that could be added to this diagram?

                                                            Figure 1. Making cities more sustainable

A recent investigation of London revealed that each resident required 6.63 global hectares (equivalent to 8 football pitches) to provide for their current levels of consumption and to absorb their waste. If one compares this to what the global sustainable footprint should be, 2.18 global hectares, Londoners consume more than three times their fair share of the Earth's resources. Would you like to know your own ecological footprint? There are several questionnaires on-line such as http://www.ecologicalfootprint.com, that you can use, my ecological footprint (global hectares) is 4.6, so I definitely can do more to improve it. Next time I will be looking at case studies of Milton Keynes and Chattannooga.