National Geographic : 2000 Oct
The Human Footprint The promise of year round golf draws thou sands of retirees to planned Sonoran com munities like Arizona's Rancho Vistoso (right). Houses here straddle natural washes and are packed together to preserve open space, but new construction projects keep claiming desert land. Relics of a more modest boom huddle on a butte over looking the now dry Gila River on the Tohono O'odham Indian Reser vation (above) near Gila Bend, Arizona. Canals and irrigated fields sustained the Hohokam people 700 years ago.