The Heat Is Online

US Crop Yields Vulnerable to Moderate Warming


Higher temperatures will harm many crops, report says

The Miami Herald, Nov. 4, 2009


Global warming would be bad news for all those amber waves of grain, and for the corn and soybeans that are plentiful throughout the Midwest.


"The grain-filling period" - the time when the seed grows and matures - "of wheat and other small grains shortens dramatically with rising temperatures. Analysis of crop responses suggests that even moderate increases in temperature will decrease yields of corn, wheat, sorghum, bean, rice, cotton and peanut crops," according to "Global Climate Change Impacts in the United States," a report based on a comprehensive review of scientific literature and government data by a team of American scientists.


Other details from the study:


-Plant winter hardiness zones - each of which represents a 10-degree Fahrenheit change in minimum temperature - in the Midwest are likely to shift by a half- to a full zone about every 30 years. By the end of the century, plants now associated with the Southeast are likely to become established throughout the Midwest.


-"Higher temperatures will mean a longer growing season for crops that do well in the heat, such as melon, okra and sweet potato, but a shorter growing season for crops more suited to cooler conditions, such as potato, lettuce, broccoli and spinach."



-Fruits that require long winter chilling periods, such as apples, will experience declines.



-"Higher temperatures also cause plants to use more water to keep cool. ... But fruits, vegetables and grains can suffer even under well-watered conditions if temperatures exceed the maximum level for pollen viability in a particular plant; if temperatures exceed the threshold for that plant, it won't produce seed and so it won't reproduce."


-Climate change is expected to result in less frequent but more intense rainfall. One consequence is expected to be delayed spring planting. In the Midwest, heavy downpours are now twice as frequent as they were a century ago.

In the Great Plains, most water comes from the High Plains aquifer. Water withdrawals outpace natural recharge. Increasing temperatures, faster evaporation rates and more sustained droughts will stress the water resource further.

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