London, Paris, Rome, New York. If civilization needed an icon, “the city” would be it. Half of humanity now lives in urban areas, a figure heading for 75 percent in coming decades.

Or maybe not. The sprawling North American city in particular is a product of the cheap energy and profligate consumption of a materially exuberant age that is rapidly coming to an end. Cities may well confront a triple specter of climate change, scarcity of energy and resources, and broken supply lines. Even the generally conservative U.S. National Intelligence Council (NIC) recently predicted that global demand for energy, food and water could easily outstrip supplies over the next decade or so, triggering trade-disrupting international conflicts.

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