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Climate Change May Increase U.S. Crop Damage From Higher Precipitation

A team of scientists, including EETD's Evan Mills, have found that increased precipitation, an expected outcome of climate change, may cause a doubling in losses of U.S. crop production over the next 30 years. This damage could cost agriculture $1.4 billion per year.

The team, including researchers from Environmental Defense and NASA-Goddard Institute for Space Studies (GISS) at Columbia University modified a widely used crop model called CERES-Maize to simulate crop yields with projected future higher precipitation. They have just published their findings in the journal Global Environmental Change.

"The climate record shows that both extreme precipitation events and total annual precipitation in the U.S. have increased over the last 100 years, especially the last two decades," says Mills. "The further increased 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 and corresponding policy implications."

Unmodified crop model and observed response to precipitation during the growing season.

Figure 1. Unmodified crop model and observed response to precipitation during the growing season. Simulations were performed using the CERES-Maize model without excess soil moisture effects on crop growth and yield. Input data were taken from the U.S. National Assessment study showing simulated versus county-level yields of corn for the period 1951-1998 at Des Moines IA.

The study focused on excessive soil moisture, which leads to damage beyond the direct impacts of the extreme precipitation events themselves because excessive moisture interferes with plants' nutrient flows, increasing the risk of plant disease and insect infestation and delaying planting or harvesting (Figure 1). If the direct damage of flooding, drought, and other anticipated impacts of climate change was included, the increase in damage would 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

They simulated maize growth in the U.S. Corn Belt in nine states, which represent about 85% of total U.S. maize production. Using data from a study period of 1951 to 1998, the team determined that because excess precipitation events are currently relatively rare, they have reduced maize yields by a relatively small amount, about 3%. This corresponds to losses of $600 million per year on average. Extended to other major U.S. crops, including wheat, cotton, soybeans, and potatoes, their results suggest that the current loss caused by excess moisture is about $1.5 billion per year.

Projections of rainfall changes from a NASA global climate model for the 2080s.

Figure 2. This image shows projections of rainfall changes from a NASA global climate model for the 2080s. This more aggressive scenario includes influences from higher population and related greenhouse gas emissions growth rate. Credit: NASA/Goddard Space Flight Center Scientific Visualization Studio.

General climate model (GCM) simulations published in the most recent U.S. National Assessment predict precipitation increases for the continental U.S. of 30% above present levels by 2030 and 65% by 2090 (Figure 2). Using the CERES-Maize model, the research team projects that the probability of damage to crops from excess soil moisture could be 90% greater in 2030 and 150% greater in 2090. This implies an average in the 2030s of $1.4 billion in losses per year beyond the current level.

The results are also significant in illustrating the importance of properly accounting for the time-differentiated patterns of events resulting from climate change. If the anticipated increases in precipitation were assumed to be distributed evenly over the year, an increase in corn yields would result, as opposed to the sharp decline in yields that would result from the tendency for the increases to occur in the form of torrential precipitation events. Some prior studies have overlooked this factor.

The paper "Increased crop damage in the U.S. from excess precipitation under climate change" by Cynthia Rosenzweig (NASA-GISS), Francesco Tubiello and Richard Goldberg (GISS at Columbia University), Evan Mills (Berkeley Lab), and Janine Bloomfield (Environmental Defense), was published in Global Environmental Change (vol. 12 pp. 197-202).

— Allan Chen

For more information, contact:

  • Evan Mills
  • (510) 486-6784; fax (510) 486-6996

This research was supported by Environmental Defense and the U.S. Environmental Protection Agency.

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