If you had time to read only one scholarly paper on drought, I'd suggest this one (published in 2007) by Cook et al. It's a comprehensive, multi-disciplinary overview that amply supports this assertion made in the first sentence of the abstract:
Severe drought is the greatest recurring natural disaster to strike North America.
The Cook et al paper reads like a forensic reconstruction of the past 1000 years, revealing
the occurrence of past "megadroughts" of unprecedented severity and duration, ones that have never been experienced by modern societies in North America. There is strong archaeological evidence for the destabilizing influence of these past droughts on advanced agricultural societies, examples that should resonate today given the increasing vulnerability of modern water-based systems to relatively short-term droughts.
Speaking of those short-term droughts, they happen to be much in the news right now. The top story in today's print edition of the New York Times starts off:
Scorching heat and the worst drought in nearly a half-century are threatening to send food prices up, spooking consumers and leading to worries about global food costs.
Many other recent stories have referenced NOAA's state of the climate report from last month (June), which included this sobering tidbit:
In 2012, about 56 percent of the contiguous U.S. was in moderate to extreme drought at the end of June. The last time drought was this extensive was in December 1956 when about 58 percent was in moderate to extreme drought.
At the same time, NOAA also reports:
While extensive, drought in 2012 has not been as severe or widespread, westwide, as it was in 2002-2005.
That brought back memories for me, when I was working on this archaeological story in the mid-2000s. It took me to a remote and magnificent part of Utah that I would periodically return to for the rest of the decade, reporting on additional facets of a controversy that grew out of the initial piece. (Here's a reflective post that includes most of the links to those stories). So for that first article, I'm interviewing two of the principal archaeologists--Kevin Jones and Duncan Metcalfe-- at the main site in Utah's Range Creek Canyon, when the conversation turns to drought. The context is Utah prehistory but the discussion also touches on the recent drought that had gripped parts of the Southwest, including Utah. At one point, Jones injects some perspective:
The drought that nearly brought this country to its knees in the 1930s wasn't all that long.
The two archaeologists then remind me of the mega-droughts I referenced above. (Incidentally, the prehistoric Plains got nailed, too.) With that context in mind, Metcalfe wonders about modern day Utah and the United States. "Could we survive a thirty year drought?" he asks rhetorically. "Absolutely not. We don't have that buffering capability in place." [This is a reference to reservoirs and other means of water storage.] Jones then muses:
Collectively, humans are very, very bad at planning for the future. We like to coast and think things are going to be the same as they are. It makes sense in terms of your own personal decision making to not always be preparing for disaster. But collectively we're just as bad at it as we are as individuals.
Now before we go any further, let me add another wrinkle to this longer-term perspective on drought. For that, we go a 2009 paper by Woodhouse et al and this section:
Although these "warm" medieval droughts may be considered conservative analogues for future droughts, it is important to recognize that there are many reasons that the mid-12th century drought cannot be considered an exact analogue for future worst-case droughts. Besides anthropogenic warming, there have been a multitude of changes in land cover throughout the Southwest due to human activities since the late 19th century. Conversion of desert and grassland to cropland, grazing, fire suppression, introduction of invasive species, disturbances leading to soil erosion and blowing dust, and the development of urban areas have all likely had impacts on regional climate. No systematic studies on these land cover changes and their impacts on climate or drought have been undertaken, but these changes are another important reason that droughts of the past are unlikely to be an exact analogue for current and future droughts. In addition, from an impacts standpoint, droughts have a much broader range of impacts on human activities today than in the past because of today's greater demands on limited water resources.
Fast forward to a post I wrote at the beginning of 2012 for the Yale Forum on Climate Change & the Media, in which I contend that
we have yet to appreciate what science has already learned about climate change in the distant past, specifically (tree ring) evidence of devastating, prolonged droughts.
This history and the contemporary land use changes and settlement patterns that Woodhouse et al describe gives us much to chew on in the context of today's drought. Here's something else from that paper we might want to keep in mind:
As far as we know, there is no reason why droughts of the duration, severity, and spatial extent experienced in the medieval period could not occur in the future. Even without the anticipated increased warming in the 21st century, droughts of the magnitude of the medieval droughts would present enormous challenges to water management agencies. Worst-case droughts of the 20th century, unlike those of the paleo record, do not contain episodes of many consecutive decades without high [water] flows, so critical for refilling of reservoirs.
Could we survive a 30-year drought? Maybe it's a question that should be part of today's anxious conversation on drought.
