The build-up of Chaco Canyon extended over many centuries and seemed to reach a peak around 1000 years ago. Then, decline set in and by AD 1300 the great pueblos and the entire canyon itself was abandoned by its creators and inhabitants. Much speculation has been made on the causes of the Chaco abandonment. Factors that have been mentioned include drought and famine, disease due to malnutrition, warfare and cannibalism, environmental degradation that caused the loss of trees, soils and the downcutting of steams, and societal inbalances created by a stratified society of haves and have nots. It is known that the time of Chaco’s decline and abandonment coincided with a period of natural global warming and enhanced aridity in the Southwest. Not only might it have been generally drier, but seasonal patterns of precipitation may have changed and droughts become more prolonged. Given that the Chacoans had weathered earlier droughts, and developed the Chaco phenomenon in a generally arid environment it seems likely that the aridity of the 12th through 13th centuries may have simply been an added pressure that pushed a society already facing strains over the edge.
Evidence suggests that the Chacoans and other ancestral Pueblo peoples moved across the landscape of the Southwest to find sustainable areas of occupation. Some Chacoans went south and there is evidence that some went northward. The great cliff palaces of Mesa Verde, Colorado show ties to Chacoan influences. The great stone pueblo at Aztec, New Mexico may have served as a regional center of sorts. However, the northern areas of southern Colorado and northern New Mexico had their own climate induced problems coupled with evidence for very high human population densities and associated demands for resources. After the 14th century the climate began to cool and may have made corn farming uncertain in the northern areas and higher mesas. Some evidence exists of violence and warfare. Perhaps the cliff palaces at Mesa Verde served a defensive role. Like Chaco, the ancient Puebloans eventually abandoned the northern areas too.
However, it is wrong to stop our account of the Pueblo peoples with the abandonment of places like Chaco Canyon and Mesa Verde and consider them lost peoples. When the Spanish arrived in the Southwest and occupied it during the 16th and 17th centuries they found a vibrant pueblo culture with large settlements of farmers along rivers such as the Rio Grande and the Little Colorado. The Rio Grande tribes, the Hopi and the Zuni farming peoples all can lay claim to long history in the Southwest and the great pueblos and settlements of the past. By the time the Spanish arrived these peoples had found a sustainable means to occupy and harvest the lands. Was the abandonment of places like Chaco and Mesa Verde indications of some sort of failure or better viewed as a choice towards sustainability that has allowed these remarkable people and their cultures to persist to the present day?