National Geographic: By 2040, the worlds population is predicted to rise to nine billion. That means two billion more mouths to feed. Even now, the earth groans under the weight of those numbers. More than 800 million people are malnourished. Another two billion are short of essential micronutrients, which affect health. A billion more consume too many calories and are obese. What can be done? In his new book, The End of Plenty: The Race To Feed A Crowded World, Joel K. Bourne Jr., a former senior editor for National...