Viewed from space, our home planet resembles a small blue marble suspended in a vast inky-black void. Earth may seem enormous to us as we go about our lives on its surface, but the astronaut’s view reveals that our planet is finite and limited. With this perspective, it becomes clear that as our population, technological power, and resource consumption all increase, so does our capacity to alter our surroundings and damage the very systems that keep us alive.

Learning how to live peacefully, healthfully, and sustainably on our diverse and complex planet is our society’s prime challenge today. The field of environmental science is crucial in this endeavor. A photograph of Earth offers a revealing perspective, but it cannot convey the complexity of our environment. Our environment consists of all the living and nonliving things around us. It includes the continents, oceans, clouds, and ice caps you can see in a photo of Earth from space, as well as the animals, plants, forests, and farms of the landscapes in which we live.

In a more inclusive sense, it also encompasses the structures, urban centers, and living spaces that people have created. In its broadest sense, our environment includes the complex webs of social relationships and institutions that shape our daily lives.