Increasing frequency of drought and decreasing yields for soybeans

Soybeans are one of the major food crops globally–along with corn, rice, and wheat.  The midwestern United States (particularly Iowa, Illinois, Minnesota, Nebraska, and Indiana) may be the primary production area for soybeans on the planet.

Rising carbon dioxide (CO2) concentrations in the atmosphere have many negative climate change impacts.  However, a long-held view (from research since at least 1997) has been that elevated CO2 may actually enhance production/yields in plants like soybeans–from the CO2 fertilization effect (CFE).  In fact, research had indicated that the CFE was expected in many cases “to mitigate the effect of drought on crop productivity”, and offset crop losses due to drought and heat stress.”  This finding had led some to conclude that climate change is not so bad for agriculture.

However, more recent research does not support this view–including research involving wheat and grasses as well as soybeans.  The yield stimulation effect of CO2 “may be far less than expected under future growing conditions that are characterized by concurrent increases in CO2 and drought intensity.”

Research by Jin, et al. (2018) found that multiple climate models project that the frequency of drought in the U.S. Midwest will increase to once every other year by 2050 (from once every 5 years at present).  “The increased frequency of drought conditions poses a formidable challenge to maintaining soybean yield progress, in part by diminishing the potential benefits of elevated CO2.”  And, the U.S. Midwest is a much more favorable environment for growing crops compared to drier regions like parts of Australia and Sub-Saharan Africa.  There, any anticipated benefits of increased CO2 are likely even less and climate change disruption to crop yields will likely be even more.

While genetic engineering of soybeans and a major shift to irrigation could help “stabilize soybean yield,” the challenges are formidable and diverse.

Will society accept more genetically-modified crops?  And, as droughts become more frequent and more intense, where would the extra water come from for greatly-expended irrigation?  What choices will we make between water for people and water for crops?  And, what about heat stress?  The research projects “a sharp decline” in soybean yields in the period 2071-2090 as a result of greater heat stress alone.

Greater heat, more frequent and intense droughts, rising CO2 levels happening all at the same time–all these factors point to plateaus and declines in major food crop yields globally within the lifetimes of us and our children.

(Kevin Engel, December 1, 2018)

For more information about the impacts of climate change on agriculture, search the Science Primary Literature Database and the Headline Science Database.

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