Why aren’t more people engaged in actions that would help mitigate climate change? The psychological “dragons of inaction” that impede green behaviors fall into seven “genera,” each with multiple “species” of barriers to pro-environmental behavior. Collectively, they represent a formidable challenge to policy makers, not only because there are so many of these dragons, but also because policy makers will need to learn much more about which dragons impede which sorts of people in order to target policies cost-effectively. Some people, dubbed “mules,” carry heavy loads of responsibility as they take major steps to mitigate climate change. Others are “honeybees” who help the environment, but without intending to do so. Too few people fall into either of these categories to make a real difference for the climate, the author writes, but he identifies five behavioral-science strategies that might help overcome the psychological barriers to climate action.