WASHINGTON, DC, October 31, 2002 (ENS) - Increased flooding, an expected outcome of climate change, may cause a doubling in losses of agricultural production over the next 30 years, a new report warns. An increased frequency of extreme precipitation events has been observed over the last 100 years in the United States. Global climate models project that similar trends may continue and even strengthen over the coming decades, due to climate change.
Now, a study using computer climate and crop model simulations predicts that U.S. agricultural production losses due to excess rainfall may double in the next three decades, resulting in an estimated $3 billion per year in damages.
Cynthia Rosenzweig and Francesco Tubiello, researchers at the Goddard Institute for Space Studies and Columbia University, New York, and the other authors of this study, found that current assessments of the impacts of climate change on agriculture have not accounted for the negative impacts on crops from increased precipitation and floods.
This aerial view of the Iowa River shows areas left inundated with water after a 1993 flood. The excess water drowns crops, increases the risk of plant diseases and insect infestation, and can delay planting and harvesting. (Photo courtesy U.S. Geological Survey) To close this information gap, the researchers modified an existing crop computer model to simulate the extent to which excess soil moisture from heavy rain might damage crop plants. "The impacts of excess soil moisture due to increased precipitation need to be taken into account because of associated crop losses and potential financial damages," Rosenzweig said.
The researchers argue that while droughts receive the most attention when it comes to assessing the impacts of climate change on agriculture, excess precipitation should also be a major concern. The 1993 U.S. Midwest floods, for example, caused about $6 to 8 billion in damages to farmers, accounting for about half of the total overall losses from the flood, according to the Federal Emergency Management Agency (FEMA).
"The Federal Crop Insurance Corporation paid out $21 billion between 1981 and 2000," said Evan Mills, a scientist in Berkeley Lab's Environmental Energy Technologies Division, and a coauthor of the paper. "Unless greenhouse gas pollution is brought under control, damage to crops from flooding will probably escalate, raising payments from government insurance programs and lowering the reliability of the U.S. crop supply. Action taken to slow global warming will protect U.S. farmers and agriculture, as well as taxpayers."
The study modifies a standard crop model called CERES-Maize to simulate yields under projected future climate conditions of heavier rainfall and shows that damage due to excessive soil moisture alone will increase crop production losses compared to present levels.
Heavy downpours increase the risk of plant disease and insect infestation and cause delays in planting and harvesting. Additional negative effects, such as direct physical damage to crop plants from heavy rains and hail, were not estimated in this study.
"Extreme precipitation events and total annual precipitation in the U.S. have increased over the last 100 years, especially the last two decades," said Janine Bloomfield, an Environmental Defense senior scientist and coauthor of the report. "Aggressive action to slow climate change must be taken now to lessen the risk of increased flooding over agricultural areas in the United States and the significant increases in crop damage and economic losses that could result."
The study appears in the current issue of the journal "Global Environmental Change.":
