Water, climate risks are a growing threat to U.S. corn
“No doubt, groundwater resources are being strained by corn production, especially in Kansas and my home state Texas, which face extraordinary groundwater depletion challenges,” said Bridget Scanlon, a groundwater specialist who leads the Sustainable Water Resources Program at the University of Texas. “The U.S. corn sector needs to greatly reduce its dependence on the High Plains aquifer. Failing to do so will have long-term negative consequences, including reduced agricultural productivity and less water for other uses.”
Climate Change Risks
Despite a bumper U.S. harvest in 2013 and lower corn prices in 2014, many of the drivers of high corn prices, price volatility and overall risk are likely to worsen, in large part due to climate change. Severe droughts, floods and heat waves at key moments in the corn-growing season are becoming increasingly common, causing dramatic year-to-year supply shocks. Among the recent examples: record high corn prices in the wake of extreme flooding in spring 2011 and the prolonged drought in 2012.
According to the latest National Climate Assessment released in May, the negative effects of climate change on agricultural production in the Midwest and Great Plains will outweigh any positive effects. Corn plants are particularly sensitive to high temperatures (which can reduce pollination and grain count) as well as to drought. Higher temperatures and increased water stress mean that increased irrigation for corn will be required. Given limited water availability in many parts of the High Plains, a northward shift in corn acreage is predicted. More frequent and intense precipitation events in the Midwest are also expected to negatively affect farmers’ ability to plant and increase run-off and erosion.
Fertilizer Use and Nutrient Pollution
Corn is fertilizer-intensive and every year millions of tons of nitrogen and phosphate fertilizer leach into groundwater and run off cornfields into waterways. Corn fertilizer run-off is the single largest source of nitrogen pollution to the Gulf of Mexico’s hypoxic “dead zone,” an area the size of Connecticut that is devoid of aquatic life.
Mapping county-level USDA corn production data and data on nitrogen loading from the USGS, the report finds:
- Inefficient fertilizer use in 2013 cost growers $420 million from run-off into the Mississippi River, and eventually the Gulf of Mexico. (Nitrate pollution due to fertilizer use by agriculture also costs water utilities $1.7 billion a year according to the USDA.)
- 60 corn ethanol refineries with $8.8 billion in annual production capacity are sourcing corn from watersheds with high local nitrogen pollution from agriculture.
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