Friday, March 29, 2013

Historical Drought - Yikes!

The official first day of spring arrived several days ago, but only now does it seem that the grip of winter is softening. Temperatures have reached into the 60s, some early bulbs are coming up and the birds are really starting to sing.  Normally I would be giddy with excitement about putting winter in the rear view, but not this year. Indeed, this is the first year in many that I might prefer we skip spring and summer altogether. Last year's drought is still too heavy on my mind. I worry that we have not yet recharged our soil moisture, and if we have a repeat of last year, we will dry up and blow away!

Hopefully my fear is misplaced, but if we actually take a much closer look at historic droughts on the Great Plains, we'll see that our recent droughts (including the last few years and the Dust Bowl years) pale in comparison to some droughts that lasted for decades in centuries past. Check out this fascinating study from the Kansas Geological Survey: This report investigates past drought occurrences from paleoclimate records over the last 1000 years. In particular, it focuses on Palmer Drought Severity Index (PDSI) reconstructions calculated from annual tree-ring chronologies - including tree rings from Nebraska's Sandhills. 

Figure 4. Mapped spatial patterns of the 1930s and 1950s droughts using instrumental PDSI data. Figure modified
from Stahle et al. (2007).

Yikes! What a scary picture this study paints. It is very likely that we've been living in an unusually wet period over the last century and a half. Hmmm. Of course we can't predict the future but we can all bet our right arms that periodic drought will be a part of the climate here for a long-darn time to come. This reality should inform our decision making regarding trees and landscapes. I apologize for this scary and depressing blog post. The next one will be better!