Some threats to the environment, like acid rain and stratospheric ozone depletion, emerged fairly rapidly, and abrupt threats like an oil or toxic chemical spill demand an immediate response. But most environmental problems have the opposite character: they involve “slow threats,” where small, hardly noticeable changes add up over time to produce large impacts. Nearly all of the most serious environmental problems we face involve slow threats. This Comment explores insights from several different fields—evolutionary psychology and neuroscience, behavioral economics and decision theory, social psychology, journalism, and political science—to gain a better understanding of why it is so difficult to galvanize attention to slow environmental threats and sustain efforts to deal with them.