The need to protect our environment is urgent, and psychology can contribute to accomplishing this goal. Combating climate change, resource exhaustion, species extinction, and other problems is an admirable goal, but such efforts will fail in the long run if the population growth that creates or exacerbates the other problems is not addressed. The large and growing human population inevitably demands more and more resources. In this comment on Clayton et al. (2016), the author proposes that psychology can identify reasons why the underlying population issue is not adequately addressed and can suggest ways to improve the situation.