In 1540 Francisco Vasquez de Coronado introduced the first domestic livestock to the American Southwest. Over the subsequent four centuries, cattle, horses, and sheep have created a massive ecological experiment on these arid grasslands, changing them in ways we can never know with certainty. The Appleton-Whittell Research Ranch in the high desert of southeastern Arizona is an 8,000-acre sanctuary where grazing has been banned since 1968. In this spirited account of thirty years of research at the ranch, Carl and Jane Bock summarize the results of their fieldwork, which was aimed at...