Climate Change and Midwest Agriculture

This year, farmers will collect a record harvest of corn and soybeans in the United States, according to the USDA. This is good news for a world increasingly concerned about both a growing population and the agricultural challenges produced by advancing climate change. Predictions by the United Nations put global population at around nine billion by 2050, with the possibility of this being the eventual stable resting point of human population due to decreasing fertility rates around the world. Global food production needs to increase substantially—around 70% according to the FAO— by 2050 in order to feed more mouths and increasingly affluent populations seeking more animal products. As a major breadbasket of the world, the Midwestern U.S. will play a significant role in meeting these demands.

As the capstone to the Workshop on Climate Change and Agriculture in the Midwest hosted by the International Center for Advanced Renewable Energy and Sustainability at Washington University, Professor David Lobell of Stanford University presented on his research into the impacts of climate change on agricultural production in the Midwest. 

Dr. Lobell had two themes: First, respect the problem. Although rising CO₂ levels may improve photosynthetic efficiency to a degree, the global increase in temperature is a net drawback to productivity. Second, we can address the problem rationally. Knowing how crops will likely respond to these stresses can help scientists identify the traits that can help meet production requirements.

The most dramatic impact of temperature increases will be reduced relative humidity. As the air warms, it can hold more water. Yet without an increase in water vapor, the relative humidity will decrease significantly. For us humans, that will hopefully offset the effects of hotter summers; we curse humidity in the Midwestern August. However, plants are exceptionally susceptible to humidity, especially when flowering.

In a tie-in to my own research, pollen, which comes to a sort of equilibrium with its environment, is easily damaged if the air is too dry when the flower opens. As it happens now, corn typically flowers during the hottest weeks of the summer, leaving its pollen susceptible to decreasing humidity. Less water vapor in the air also means the plant will transpire much more, increasing the amount of water needed in the soil to keep the crop happy and productive.

How do we combat this inherent weakness? Perhaps plant biologists can identify traits, or contribute new genes, that make crops use water more efficiently and protect pollen from excessive desiccation. Intensive research is being done in these areas already.

One idea that Dr. Lobell put forward was new to me, but apparently not to some farmers in the Southern United States: double cropping. With the right climate, fields can be planted with wheat in the fall to harvest in the spring, with just enough time left over to harvest soybeans in the fall. Under these conditions, flowering occurs outside the hottest months, and yield can be protected from the extreme heat to an extent. In fact, as the climate warms, Midwestern states will acquire longer growing seasons that make this option available to more farmers. Although this strategy does not necessarily out-produce the incredibly abundant maize crop, it is an example of alternatives immediately available to farmers even without significant improvements in crop germplasm.

Other strategies for helping crops cope with increasing temperatures will likely involve infrastructure, such as how to provide plants with enough water without losing as much to the soil and evaporation. Smarter irrigation systems may help in this goal.

The bottom line from Dr. Lobell’s talk is that adapting already-productive areas like the United States Midwest to climate change will require multiple strategies, because the effects of a warming world are multiple. This will require the sustained efforts of plant scientists, engineers, and innovative farmers. I, for one, am hopeful about the future of agriculture. Us humans seem to do a decent job of getting ourselves out of a mess, even if it is at the last moment. Let’s hope that’s the case here.