"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.