This article was written by Alex Steffen in January 2008. We're republishing it here as part of our month-long editorial retrospective.

I've been thinking about the fate of declining suburbs, bombed out shrinking old industrial cities and the drying up ghost towns of the high plains, when I came across a journal note mentioning something Bruce Sterling said to me this fall in San Francisco:

"The ruins of the unsustainable are the 21st century's frontier."

Discuss. Or just mull.

The Ruins of the Unsustainable is part of our month long retrospective leading up to our anniversary on October 1. For the next four weeks, we'll celebrate five years of solutions-based, forward-thinking and innovative journalism by publishing the best of the Worldchanging archives.