Des Moines Register: The world already counts on Iowa to meet food production needs. A warmer world will count on Iowa even more. If the Earth heats up as climate forecasts suggest, agricultural production is likely to fall in many parts of the world, especially in poor countries near the equator and in Australia, a key producer of grain. But parts of the United States, including Texas and states in the Southeast, also could see smaller harvests because of declines in rainfall. One study estimates …