In the 1970s, the oil crisis unleashed many things, including a visionary idea of cities becoming solar-powered, neighborhood-centric, green-roofed oases (instead of polluted, congested, soul-deadening wastelands as they were sometimes depicted).

Activist and writer Brian Tovar sees a re-emergence of the Green Cities ideal now due to the growing urgency of global warming.

Tovar thinks today's movement lacks the visionary passion of the urban...