The conservation ethic is an ethic of resource use, allocation, exploitation, and protection. Its primary focus is upon maintaining the health of the natural world: its forests, fisheries, habitats, and biological diversity. Secondary focus is on materials conservation and energy conservation, which are seen as important to protect the natural world. To conserve habitat in terrestrial ecoregions and stop deforestation is a goal widely shared by many groups with a wide variety of motivations. The consumer conservation ethic is sometimes expressed by the four R's: " Reduce, Recycle, Reuse, Rethink." This social ethic primarily relates to local purchasing, moral purchasing, the sustained and efficient use of renewable resources, the moderation of destructive use of finite resources, and the prevention of harm to common resources such as air and water quality, the natural functions of a living earth, and cultural values in a built environment.