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COMPUTER
MODEL SUGGESTS FUTURE CROP LOSS DUE TO POTENTIAL INCREASE IN EXTREME RAIN EVENTS
OVER NEXT CENTURY
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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 30 years, resulting in an estimated $3 billion per year in damages.
Cynthia
Rosenzweig and Francesco Tubiello, researchers at the NASA 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. In an effort 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 roughly half of the
total overall losses from the flood, according to the Federal Emergency Management
Agency. Overall precipitation and extreme rain events are projected to increase
in the future because of stronger water cycle dynamics associated with global
warming.
Global
climate model simulations used in the study project increases in total precipitation
and in the number of extreme precipitation events in the Corn Belt and on average
for the continental United States. Over the Corn Belt states, the average number
of extreme precipitation events was 30 percent above present levels in the 2030s,
and 65 percent higher in the 2090s. The same climate projections were used for
a 2001 U.S. national assessment report on potential consequences of climate change.
The
researchers also modified an existing crop model, called CERES-Maize, in order
to simulate the effects of excess soil moisture from heavy precipitation on corn
crops. The model calculates plant development, growth and final yield based on
weather, crop genetic traits and management practices. The researchers modified
CERES-Maize by adding in a function that limited the simulated plant's ability
to grow roots after three consecutive days of soil saturation. The model simulated
corn growth in nine U.S. Corn Belt states, including Kansas, Nebraska, Illinois,
Indiana, Iowa, North and South Dakota, Ohio and Wisconsin, which represent 85
percent of total U.S. corn production.
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Click
here to see climate model images based on more aggressive population and greenhouse
gas emissions growth rates. The
modified model showed that the probability of crop damage due to water-logged
soils could be even greater than the projected increases in heavy precipitation
- corresponding to 90 percent more damage in the 2030s, and 150 percent more damage
by the 2090s, compared to present conditions. To
relate the climate and crop model results to economic losses, Rosenzweig and her
colleagues used USDA economic data to estimate that damages to U.S. corn production
due to excess soil moisture currently amount to about $600 million per year. The
researchers then estimated that potential future damages to major U.S. crops due
to excess soil moisture could lead to total losses of up to $3 billion per year
by the 2030s, on average. The
study appears in the current issue of Global Environmental Change. The research
was conducted at the Climate Impacts Group of the NASA Goddard Institute for Space
Studies at the Earth Institute at Columbia University and was supported by Environmental
Defense and the Environmental Protection Agency.
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