Swelling carbon dioxide in the atmosphere cuts nutrition in food. According to a physician and researcher at the Harvard School of Public Health, increasing CO2 levels in the atmosphere are reducing the amounts of iron and zinc in crops such as wheat, rice, barley, and soybeans. Deficiencies in zinc and iron in the human diet are estimated to lead to the loss of 63 million life years annually. The full article is on the Scientific American website and originally published in Nature Magazine.