Although it was recognized in Darwin’s day that humans could affect the natural world, and that human populations were undergoing unprecedented growth, for the most part early ecologists believed they were studying pristine systems largely untouched by human activities. Today most ecologists have a much greater awareness of ways in which humans shape the natural world, be it in the form of global climate change, the introduction of novel species to new locations, or the logging of Earth’s tropical forests. Because of the dominant role that humans play in almost every ecological system on Earth, a “use-inspired” motivation often shapes ecologists’ research and teaching. They understand that scientific knowledge of ecology greatly improves our ability to grow food for ourselves reliably and sustainably, to manage pests and diseases safely and effectively, and to deal with natural disasters such as floods and fires. The greater our understanding of ecological connections, the more likely it is that we can accomplish these things without causing a cascade of unanticipated consequences for ourselves and the other life on Earth.