A thoughtful reader points out, in regard to last night's post about climate variability in the Colorado River basin, that I didn't make what I will call the Pielke Jr. point: "the problem is not the climate change but the societal changes!" (That's quoting my thoughtful reader (TR), not Pielke.)

TR is of course right. It's not climate variability per se that is the problem here. The problem is twofold. First, it's a problem that the folks who set up the system for allocation of Colorado River water didn't understand the extremes of variability that could affect the river's supplies. The second is that population and associated human systems have grown up around the Colorado River's water with no clear understanding of the variability in water availability that is inevitable in the long run. We are, as a result, extremely vulnerable to the sort of severe, sustained drought that tree ring records suggest has happend in the not-so-distant past. We're not vulnerable in the same way as the Anasazi. We son't starve. But there could be significant societal dislocations.

One thing worth doing in this context is is to examine the difference between the hunter-gatherers who inhabited the Four Corners region before the puebloans, as compared to the Anasazi. Hunter-gatherers survived droughts worse than the ones that coincide with the end of the Anasazi culture. The short answer for why is that the hunter-gatherers had apparently read Pielke, and therefore did not max out the resources, leaving them the flexibility to respond to drought when it happened. In other words, they reduced their societal vulnerability to climate variability.

The Anasazi did not read Pielke, and died.