Scientists have much to learn about predicting future climate conditions, particularly when calculating change for certain regions on the earth's globe, says Elwynn Taylor, Iowa State University Extension climatologist. Yet, he also warns that both long- and short-term warming and cooling cycles signal potential troubles ahead for Corn Belt crop production.
“Long term, we've had a natural warming that's been going on for about 20,000 years, since the last glaciers melted from on top of Des Moines,” says Taylor.
“More recently, our climate has been going through 90-year, short-term warming and cooling cycles,” he says.
If history repeats itself, Taylor says the next 90-year warming cycle would likely peak in 2025. “We haven't had any year as bad as 1936 since 1936 — when the last 90-year warming cycle peaked,” he explains. “However, the effect that people are now having on our climate might speed up the cycle a bit.”
More intense summer heat for the region — either man-made or natural — would be detrimental to corn production, warns Jerry Hatfield, a supervisory plant physiologist at the National Soil Tilth Research Laboratory, Ames, IA. He notes that the corn plant is more vulnerable to extreme heat than other row crops, such as soybeans.
“In the Corn Belt, if this (global warming) trend continues, we could see significantly reduced corn yields in the next 30-50 years,” says Hatfield. “As global warming increases, the Corn Belt would likely encounter much higher temperatures during the pollination phase of corn plant development than in (more temperate) years. We would likely see the daytime high temperatures above 95° F, which is lethal to corn pollination. We would also have higher nighttime temperatures and respiration rates, which would result in smaller grain size and less grain fill.”
RISING TEMPERATURES and CO2 levels in the traditional Corn/Soybean Belt would likely boost — rather than deflate — soybean yields compared to corn if rainfall remains ample, adds Hatfield. “Soybeans respond well to high CO2 levels by increasing photosynthesis and production,” he explains. “Temperatures aren't lethal to pollination in soybeans until they reach 104° F.”
Yet, adequate precipitation will still be the “biggest wild card” for crop production if global warming continues, he says. Hatfield cites the drought-suffering Southeastern U.S. as an example of what increased global warming might have in store for southern portions of the current Corn/Soybean Belt.
“In the Southeastern U.S., as temperatures have increased in recent years, precipitation has decreased,” he says. “So, in the Corn Belt, it may be another 10-20 years before we see a consistent negative impact of global warming on crop production, whereas in the Southeast it might occur sooner or already be occurring.”
To adapt to warmer summertime conditions, enterprising farmers could continue to expand the current Corn Belt to the north and possibly further west, says Hatfield. “However, if such an expansion were to occur, the key to good production would be getting reliable rainfall for that northwestern Corn Belt,” he emphasizes.
AN INCREASED SHIFT in soybean production to the north and west may soon transpire, concurs Mark Seeley, University of Minnesota Extension climatologist. “(With more global warming), we're estimating that soybean yields will continue to increase in the Corn Belt and decrease in the Southeast,” he says. “So, there may be a shift in crop production, where the Southeast will grow fewer soybeans and northwestern states grow more soybeans.”
Still, global warming has yet to hurt Corn Belt crop production, points out Seeley. “Over the last several years, most areas in the Corn Belt have been reporting longer frost-free growing seasons and an upward trend in growing degree days,” he says. “Generally, we've been getting region-wide boosts in corn production as a result. However, this (longer growing season) hasn't been established in the region long enough to know if that trend will hold.”
More extreme weather patterns are likely to develop if global warming continues, emphasizes Seeley. “From a precipitation standpoint, we've already seen amplified variability in the Great Lakes region in recent years — more episodes of extreme dry and extreme wet, with very abrupt transitions between the two,” he says. “According to the Intergovernmental Panel on Climate Change (IPCC), this extreme precipitation variability is now becoming characteristic of many different landscapes besides the Great Lakes region.”
If temperatures continue to climb, weather volatility will likely escalate, agrees Hatfield. “One thing we do know is that with higher global temperatures, precipitation will increase in variability,” he says. “More heat will usher in an extremely variable precipitation regime, which will wreak havoc on crop production in the traditional corn and soybean growing areas. So, the hardest thing to manage in the future, if global warming continues, will be the extreme variability in precipitation.”
CONSECUTIVE COLD, WET SPRINGS UNLIKELY
After enduring an unusually chilly, soggy spring this year, many Midwestern farmers might wonder if they should expect similar conditions in 2009. Not likely, say regional climatologists.
The last time Iowa experienced two consecutive wet, cold springs was 1992 and 1993, says Elwynn Taylor, Iowa State University Extension climatologist. “It just doesn't happen very often,” he says. “Only about one out of six springs are either too wet or too cool to be ideal.”
Few years exhibit spring weather similar to what occurred in 2008, says Mark Seeley, University of Minnesota Extension climatologist. To experience similar back-to-back years is even rarer, he adds.
“The aberration that we had this spring with cool, persistent wetness was a fairly close match to 1996 - so it's been 12 years since we've seen this,” says Seeley. “Historically, there are just very few years when you might see back-to-back wet, cool springs.”
On the other hand, Taylor points out that if next spring starts out unusually cool, then the odds increase that it will also be wet. “There is some connection between hot-and-dry and cool-and-wet weather - especially in Iowa,” he says. “So, it's more likely to have a cold, wet spring than a cold, dry one.”