Why do urbanized societies need stretches of uninhabited and undeveloped land?

Large stretches of undeveloped land outside cities provide natural resources needed to support urban populations. This includes providing city dwellers with timber, food, and other resources. Areas of natural land of all sizes close and far from urban centers provide ecosystem services, including purification of water and air, nutrient cycling, and waste treatment. Natural lands provide escape from the stresses of urban life. They provide open space, greenery, scenic beauty, and places for recreation. They also provide habitat for wildlife, which serves to satisfy biophilia, our natural affinity for contact with other organisms. In addition to the utilitarian reasons cited above, many people feel an ethical obligation to preserve wild landscapes and biodiversity for the sake of nonhuman organisms and/or the integrity of ecological systems.