November 15, 2002
Berkeley Lab Science Beat Berkeley Lab Science Beat
As climate changes, more rain and snow could increase U.S. crop damage
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Scientists have found that increased precipitation, an expected outcome of climate change, may cause losses of US corn production to double over the next 30 years — additional damage that could cost agriculture $3 billion per year.
Click here to view an MPG movie of before-and-after flood damage to crop lands.

The team who made the finding includes researchers from NASA's Goddard Institute for Space Studies (GISS), the GISS office at Columbia University, the Department of Energy's Lawrence Berkeley National Laboratory, and the nonprofit organization Environmental Defense. The researchers modified a widely used crop model called CERES-Maize to simulate crop yields under projected future climate conditions of higher precipitation. They have recently published their findings in the journal Global Environmental Change.

"The climate record shows that both extreme precipitation events and total annual precipitation in the US have increased over the last 100 years, especially the last two decades," says Evan Mills, a scientist in Berkeley Lab's Environmental Energy Technologies Division. "The further increase of precipitation expected in a changing climate regime could lead to increases in crop damage. The goal of our study was to estimate the potential magnitude of this damage."

Crop damage can persist even after flood waters go down. (Click here to view enlarged image.)

The study focused on excessive soil moisture, which leads to additional damages beyond the direct impacts of the extreme precipitation events themselves, by interfering with plants' nutrient flows, increasing the risk of plant disease and insect infestation, and delaying planting or harvesting. If the direct damages of flooding were included, total increase in damages would likely be even greater.

"The Federal Crop Insurance Corporation paid out $21 billion between 1981 and 2000," says Mills. "Increased damage to crops will probably result in an increase in payments from government insurance programs like these."

Estimating crop losses from heavy precipitation

The research team modified the CERES-Maize crop model to simulate damages to crops from excess soil moisture caused by heavy precipitation. They simulated maize growth in the US Corn Belt in nine states representing about 85 percent of total US maize production (Kansas, Nebraska, Illinois, Indiana, Iowa, North and South Dakota, Ohio and Wisconsin).

Illinois corn crops were ruined in the 1993 Mississippi River flood.  

Using data from 1951 to 1998, the team determined that, because excess precipitation events are currently relatively rare, they reduced maize yields by a relatively low amount, about 3 percent. This corresponds to losses of $600 million per year on average. Extended to other major US crops, including wheat, cotton, soybean and potato, their results suggest that the current loss caused by excess moisture is about $1.5 billion per year.

General climate model (GCM) simulations published in the most recent US National Assessment (Potential Consequences of Climate Variability and Change, Overview Report, 2001, US Global Change Research Program) project precipitation increases for the continental US of 30 percent above present levels by 2030 and 65 percent greater by 2090.

Using the CERES-Maize model, the research team projects that the probability of damage to crops from excess soil moisture could be 90 percent greater in 2030 and 150 percent greater in 2090. This implies that in the 2030s, average losses per year will be $3 billion beyond the current level.

"These are costs that would be borne by the impacted businesses, or transferred to national and private insurance companies," says Mills.

The paper, "Increased crop damage in the US from excess precipitation under climate change," by Cynthia Rosenzweig (NASA-GISS), Francesco Tubiello, Richard Goldberg (GISS at Columbia University), Evan Mills (Berkeley Lab), and Janine Bloomfield (Environmental Defense), has been published in Global Environmental Change, vol. 12, 2002.

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