Village depopulatiom in southwest reflects successful agriculture

Village depopulatiom in southwest reflects successful agriculture Southwestern peoples tended to move often -- locally or regionally -- when natural resources became depleted or the climate was changing -- by moving up or down in elevation or crossing over to nearby, unoccupied valleys, said Cordell.

The Greater Southwest is either desert or semi-desert and large portions of the region are at high elevations, she noted. Clever farming strategies allowed ancestral Pueblo people on the higher Colorado Plateau and adjacent highlands to overcome challenges like too little moisture and too short growing seasons for hundreds of years.

They used "ingenious devices" to conserve moisture and moderate temperature at ground level, including moving run-off water to agricultural fields, planting grid-based gardens, placing crops at the mouths of arroyos and in dunes and building check dams and terraces. They even spread gravel mulch over vast field systems that not only slowed run-off, but also moderated temperatures at ground level.

Since gravel mulch absorbs heat from the sun in the daytime and releases it slowly after sundown, they were able to extend the frost-free periods in these areas for several weeks. "Along the Chama River in New Mexico, Pueblo people even grew cotton, something not done in that location where the growing season is marginal even for corn," she said.