Many dryland regions contain archaeological remains which suggest that there must have been intensive phases of settlement in what now seem to be dry and degraded environments. Many people have speculated about what must have happened to turn past glories into present day barrenness, opinions generally dividing between climatic change and human activity as the primary culprit. Perhaps climate shifted to greater aridity, perhaps catastrophic but short-term droughts became too frequent? Or was it that people sowed the seeds of their own destruction, for example by removing trees or developing...