Certain behaviors enacted by individuals and groups (for instance, deciding whether or not to conserve energy or recycle resources) have a profound impact on the environmental quality and healthfulness of our physical surroundings. This lecture highlights the vital role of natural capital (such as nutrient-rich soils and unpolluted waterways) in generating a variety ecosystem services such as the production of food, energy, and pharmaceuticals. Important demographic and environmental trends are discussed, including the rapid growth of the world’s human population from the 1900s onward (especially in developing countries), the depletion of the earth’s atmospheric ozone layer, the “greenhouse effect” and global warming. Alternative strategies for promoting environmentally protective behavior are considered, including the provision of financial incentives, behavioral feedback, and the activation of social norms that encourage sustainability and resource conservation. The importance of encouraging high-leverage behaviors that reduce energy consumption or improve the efficiency of its use is emphasized.