A Times investigation revealed that in much of the United States, communities and farms are pumping out groundwater at alarming rates. Aquifers are shrinking nationwide, threatening supplies of drinking water and the country’s status as a food superpower. Christopher Flavelle, who covers climate adaptation for The Times, went to Arizona, the state at the forefront of the crisis, and looked at one especially controversial idea to address it: desalination. Guest: Christopher Flavelle covers climate adaptation for The New York Times.