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.

This is unfamiliar ground. Since World War II, politicians and planners have shaped cities with no regard for resource use or ecological concerns. Today’s land-grabbing, auto-dominated, fuel-inefficient metropolises have evolved into parasitic black holes, sucking in excessive megatons of energy and materials from all over the globe and spewing out volumes of (often toxic) waste. In North America, buildings and urban infrastructure account for 40 percent of material consumption and a third of energy use. High-income cities have an ecological footprint—the dispersed area of land and water required to supply their needs and assimilate their wastes—that is several hundred times larger than their political areas.

All this must change. Climate science indicates that to have even a chance of avoiding a catastrophic increase in mean global temperature, the worldwide economy must be largely de­carbonized by 2050. The NIC argues that the U.S. should actually complete its transition by 2025. Such goals pose an unprecedented challenge to urban authorities at all levels.

To begin to meet that challenge, state and municipal governments must create the land-use legislation and zoning bylaws that urban planners need to consolidate metropolitan areas and smartly raise their density. Compact cities can boost their inherent urban efficiencies to unprecedented heights by exploiting the following characteristics:

  • A high proportion of multiple-family housing, which reduces per capita consumption of land, infrastructure and just about everything else.
  • Multiple options for recycling, reuse and remanufacturing of materials, along with skilled people for those activities.
  • Car-free mobility, through investments that make walking, cycling and public transit viable.
  • Co-generation of electricity and use of industrial waste heat to reduce per capita energy consumption.
  • Improved livability with cleaner air, easy access to amenities, and a greater proximity of shopping and employment.

Efficiency gains are not enough, however. Sustainability and security demand that cities become more self-reliant. Urban designers must rethink cities as complete ecosystems. The most resilient option might be a bioregional city-state in which a densely built-up core is surrounded by supportive systems. Without becoming isolationist, such bioregions would produce much of their own food, fiber and water and recycle their waste. By being less reliant on imports, they would be partially insulated from climate vagaries, global resource shortages and distant military conflicts. And because inhabitants would depend on local ecosystems, they would have a powerful incentive (currently absent) to manage their resources more sustainably. The aggregate effect would be global sustainability.

Seem over the top? Perhaps. But our rethinking of cities must match the challenge. Scientists are deeply worried; you should be, too. If we can’t save our cities, we won’t save ourselves.

Note: This article was originally printed with the title, "More Sustainable Cities".