Ted, in our part of northern New Mexico the Native American populations reached a high point after about AD1350, declining rapidly after Spanish colonialization. While there is evidence of population decline from periodic drought and environmental degradation, the land was obviously productive (locally some pueblos seem to have subsisted on corn and other crops, hunting and gathering, and raised turkeys for feathers and food) for those who had the knowledge and skill to utilize a diversity of resources. Certainly, as throughout North America, there were intricate and effective trading networks that brought in resources from at least as far away as the Pacific coast and Central America.
Our major environmental problem now is the declining water table. Ancient pueblo sites are located on land which once had an abundance of springs and seeps. Cisterns were also fastioned to collect snow melt and seasonal rains. Now wells are having to be dug hundreds of feet deeper than even in the 1950s or later. We are considering plans to re-create meanders on one of our local rivers (to offset the Corps of Engineers terrible concrete straightening of the river channel) in order to encourage riparian growth and recharge some of the ground water that existed prior to mining and heavy livestock concentrations.
