Growing pains

FARMING is more efficient than ever. But the search for high yields has also made it more concentrated. From the wheat in steaming noodles to the maize of fresh tortillas, just 30 crops now sate almost all of humanity’s nutritional needs.But monoculture carries great risks. A single disease or pest can wipe out swathes of the world’s food production, an alarming prospect given that its growing and wealthier population will eat 70% more by 2050 (see ). The risks are magnified by the changing climate. As the planet warms and monsoon rains intensify, farmlands in Asia will flood. North America will suffer more intense droughts, and crop diseases will spread to new latitudes. Pests are on the move, too. Since the 1960s, unwanted beasties, spared harsh winter frosts, have moved polewards at an average of around 3km (2 miles) a year.