For many of us in affluent regions, our bathroom scales indicate that we get more than enough to eat, which may lead some to believe that it is easy, perhaps too easy, for farmers to grow our food. On the contrary, modern agriculture requires vast areas of land, along with regular infusions of water, energy and chemicals. Noting these resource demands, the 2005 United Nations–sponsored Millennium Ecosystem Assessment suggested that agriculture may be the “largest threat to biodiversity and ecosystem function of any single human activity.”