In 1800 3% of humans lived in cities. By 2050 over 2/3 of us will. We're becoming an urban species, and this trend is going to dramatically change our political, economic and, um, environmental environments.

We learned that from 19.20.21, a new multi-year research project that's exploring the phenomenon of the "supercity." Specifically, it will examine 19 cities with 20 million people in the 21st century.

Reader Kate Andrews tipped us off to this.