The end of January may not be the best time to whine about the unusually cool summers we’ve been experiencing in these parts (“Seventy degrees in August? I’m freezing!”). But at the annual meeting of the American Meteorological Society earlier this week, two fascinating studies linked cooler, wetter summers to our massive conversion of Midwestern real estate to row crops like corn.
As was reported on the Science News website today, one analysis done by Northern Illinois University found that from 1970 through 2009, average high temperatures at study sites in Iowa and Illinois during July and August were between .5 and 1 degrees Fahrenheit cooler than they were between 1930 t0 1969. And average rainfall for July and August from the 1970s through 2009 was around .33 inches higher each month when compared to the period covering the 1930s through the 1960s.
There’s a link between the cooler temperatures and the wetter summers: it turns out humid air warms more slowly. There also may be a link to that wetter air and the agronomic transformation of the Midwest. Around 57 percent of farmland in the region was planted to row crops in the 1930s; today that figure is more like 97 percent. Corn and soybeans pump tremendous amounts of water from the soil into the air, making for more humid summers, and thus a whole lot of air that heats up slowly.
Interestingly, the trend of placing row crop seeds in more dense planting patterns may also be increasing farmland’s ability to moisturize the atmosphere. In fact, the Northern Illinois researchers say this technique has increased the numbers of water-pumping plants per acre by around 60 percent over the years.
If that wasn’t enough, all that increased irrigation taking place in the Great Plains in recent decades is pumping even more water into the air, according to a Rutgers University study that was presented at the American Meteorological Society meeting. A lot of that unfettered groundwater is used by crops, evaporates into the air and then moves downwind to the Midwest and beyond to form rain clouds.
“The result has been an approximate doubling of the surface water available for evapotranspiration, most of which evaporates rather than runs off or returns to groundwater. Using gridded precipitation observations covering 1900-2003 over North America, we show that this enhanced evapotranspiration has increased precipitation by 25-50% downwind of the Ogallala Aquifer during July,” concluded the Rutgers scientists.
So what? That just means lower air conditioning bills and an economic stimulus package in the form of higher umbrella sales, right? Well, as with any natural cycle, we short-circuit this one at our own risk. Unforeseen consequences start popping up real quick.
For example, I recall a visit I had with southeastern North Dakota grain farmer David Podoll a few years back. He was finding that it was getting increasingly difficult to raise small grains such as wheat and rye because of the rise in moisture-related diseases he was seeing in his fields. (He was also finding that doing field work was an increasingly unpleasant task, as all those wet spots were producing hatches of mosquitoes he’d never seen before.)
Many of Podoll’s neighbors saw it as a temporary wet phase, one that would pass as quickly as a summer thunderstorm. It hasn’t. And somehow Podoll, an obsessive observer and record keeper of the land’s comings and goings, knew it wasn’t.
That’s why several years ago he and some other like-minded farmers began working with plant scientists in North Dakota and Minnesota to breed some “natural resistance” back into small grains like rye, oats and wheat so that they can better weather this new climate situation.
Will Podoll and company develop grains that consistently produce during cool, wet summers? Who knows. But I feel a little better knowing that at least one farmer noticed before the sceintific “experts” that things were out of whack with the natural scheme of things.