Corn Harvesting (image) Stanford University Caption A combine harvester reaps, threshes and winnows its way through a field of corn at harvest time. Yields in the US, Canada and northern Mexico have yet to feel the impact of global warming. Credit UDSA Usage Restrictions None Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.