Does size matter?

In the political discourse and scientific literature on urban sustainability, particular attention is being paid to megacities. ¹ World Bank President Robert Zoellick, for example, stated in a speech delivered to the fourth climate summit of the C40 (the Large Cities Climate Leadership Group) that megacities are responsible for about 80 percent of greenhouse gas emissions. Similarly, the United Nations Human Settlements Programme (UN-Habitat, 2011: 92, 71) underscores that ‘because of their sheer size,’ megacities are critical sites of current and future greenhouse gas emissions, with Asian megacities in particular ‘driving the increase in coastal flood risk globally.’ Accordingly, Heinrichs et al. (2012: 5, 8) discern a ‘risk habitat megacity’ because, due to ‘the concentration of people and values […] the extent of a potential risk event is estimated to exceed the capacity of a megacity to react, with the consequence of particularly high losses.’ All in all, therefore, it is ‘no exaggeration to suggest that megacities will play a central role in the future of human civilization, and that meeting the challenges they present is a key to global environmental and social sustainability’ (Sorensen and Okata, 2011: 1).