ABSTRACT
Sustainability does mean something both important and new. 1 It speaks of the greatest change in human thought and behaviour for 3000 years. It is fundamentally about the global environment. It is also about cities. A simple metaphor may be useful. Think of having a good soak in the bath. Before getting out and grabbing a towel, lie there a moment longer and pull out the plug. The water level immediately begins to drop. A colder perimeter creeps round your body. A little whirlpool or vortex forms above the plug hole. Now think of the bathwater as the environment. The city is the vortex created by swallowing up the environment - it is the energy, the water and the materials consumed by city dwellers. There are two ways of keeping water in the bath. Put the plug back in, or run the taps at the same rate as the water going down the waste pipe - or do some combination of the two: stem the flow, run the water. Maintaining the water level and keeping the water at a comfortable temperature is what 'sustainability' means in the world of this little metaphor.
