In July 2012 three of India's regional electric grids failed, triggering the largest blackout on earth. More than 620 million people—9 percent of the world's population—were left powerless. The cause: the strain of food production from a lack of water. Because of major drought, farmers plugged in more and more electric pumps to draw water from deeper and deeper belowground for irrigation. Those pumps, working furiously under the hot sun, increased the demand on power plants. At the same time, low water levels meant hydroelectric dams were generating less electricity than normal.