Ah, that first messy bite of local sweet corn, fresh from the farm stand, farmers’ market or your own backyard. Boiled, steamed or roasted on the grill—it’s a cherished ritual signifying the final flourish of summer.   

“Maize” is the correct name for this remarkable species of grass, although “corn,” an 18th-century English word that was used generically to describe any staple grain or cereal food crop—including oats or wheat—persists in the English-speaking world. 

Maize has been cultivated by humans for more than 9,000 years, starting in the highlands of central Mexico. It was one of the noted food contributions of the New World to the old, along with potatoes, tomatoes, chili peppers and sweet potatoes. In the Native American tradition, maize was planted with beans and squash in a polyculture called the Three Sisters, which maximized resources and helped replenish the soil. 

Nowadays, maize provides a staple food source around the world, and more is grown worldwide than wheat or rice. In 2020, the U.S. produced almost a third of the global crop, followed by China, Brazil, Argentina and Ukraine. Maize is transformed into a wide variety of foodstuffs, from cornstarch, corn syrup and corn oil to bourbon whiskey. Field corn and silage are important animal feeds. Ethanol fuels are a more controversial corn product, accounting for about 40 percent of the U.S. crop.

Corn has become an environmental and nutritional battlefield, mainly because of the ways we have messed with it over the centuries, from conventional growing methods to genetic engineering. In the 1970s, Secretary of Agriculture Earl Butz famously reversed New Deal-era subsidies for corn, which had encouraged farmers to limit corn production in order to prevent gluts and price collapse. Butz’s maximalist corn policy led to the decline of small family farms and the industrialization of the U.S. food system. In turn, industrialized farming methods have accelerated global warming, and corn is right in the middle of the problem, with environmental impacts that include high GHG emissions, groundwater depletion, overuse of fertilizers and runoff that causes “dead zones” in rivers and oceans, pesticide and herbicide use, degraded air quality and soil erosion due to intensive monoculture. 

In 2019, researchers from the universities of Minnesota, New Mexico, Washington and California, as well as the University of Oxford, published a study that used county-level data on agricultural practices and production to develop a comprehensive life-cycle-emissions inventory for maize. It was the first major study to quantify the damaging effects of particular methods of food production on air quality and the associated health risks. In particular, the study examined pollution from atmospheric particulate matter with a diameter of less than 2.5 micrometers (PM2.5), which has been linked to respiratory illnesses, cardiovascular disease, diabetes and some birth defects. Correlating emissions data with census and public health data county by county, the researchers concluded that corn production accounts for 4,300 premature deaths related to air pollution every year in the United States, and even pinpointed the Corn Belt counties that bear the brunt. Air pollution associated with corn production is largely due to the intensive use of nitrogen fertilizers that release ammonia into the atmosphere, where it reacts with nitrogen and sulfur oxides to produce PM2.5.  The researchers estimated that the resulting health damages cost the U.S. $39 billion a year. Their recommendations include changing the fertilizer type and methods of application, and reallocating the geographic distribution of maize production to reduce the intensity of industrialized monoculture.

Climate change may speed that geographic reallocation. In 2022, researchers at Penn State published a study of the future impacts of global climate change (global warming) on both irrigated and rain-fed corn yields from the 2020s to the 2090s. The study focused on the Corn Belt states of the Midwest, but its conclusions have repercussions for the northeastern U.S. and for the rest of the world, because corn and its various products are so integrated into the world food supply and economy.  

The team analyzed potential U.S. corn crop decline based upon 18 different climate-warming scenarios, and found that yields for rainfed corn crops were likely to drop by as much as 21.5 percent, depending on the specific concentrations of GHG emissions and subsequent warming projected under the different scenarios. Declines for irrigated corn crops were slightly lower but still significant, ranging as high as 15.6 percent over the study timeframe. 

Depleted and degraded water supplies in the traditional corn-producing states, combined with the ongoing increase in air temperature, warmer overnight temperatures and atmospheric moisture demand, could cause a significant shift in corn production to the eastern U.S., including Pennsylvania. The study urged policy-makers to prepare for that eventuality. 

Will we have the wisdom and forethought to avoid the problems that intensive monoculture, groundwater depletion and the air pollution associated with industrialized farming have created in the Midwest?