ocr: both environmental and social factors were involved. The climate of the region is semiarid today, and there is evidence that a long-term decline in annual rainfall brought the city to a similar condition in the latter half of the first millennium A.D. Even before then, deforestation of the surrounding hills may have begun a process of erosion that caused a decrease in the soil moisture available for crops. Although persistent drought would have presented increasingly serious problems for those who fed the city, food shortages might have been the lesser of its consequences. More ominous would h ...
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