The Cobra Effect - a particularly extreme form of unintended consequences - isn't limited to India and Vietnam. In China, the technically successful Four Pests eradication campaign led to tremendous ecological disaster, as the mass murder of sparrows led to a plague of ravenous locusts. In part two of this week's two part episode, Ben, Noel and Max explore what went wrong, how it affected later generations, and what the Cobra Effect can teach us about unforeseen consequences.