Megadroughts could return to southwestern U.S.

By Jenny Howard Almost a thousand years ago, in the arid climate of the southwestern United States, the Chacoan culture flourished. Ancestors of southwest Native American tribes today, Chacoans built impressive multi-storied stone buildings with a far-reaching trade system selling colorful macaws for turquoise. But a desperate lack of water—a megadrought—caused the advanced civilization to seemingly vanish within a …