Water occurs as a liquid on the surface of Earth under normal conditions, which makes it invaluable for transportation, for recreation, and as a habitat for a myriad of plants and animals. The fact that water is readily changed to a vapour (gas) allows it to be transported through the atmosphere from the oceans to inland areas where it condenses and, as rain, nourishes plant and animal life Read more

The social-ecological model emerged from ecological systems theory (Bronfenbrenner, 1979), which explicitly sought to examine transactions between persons and their environments. The model stresses cross-level influences, in which community or organizational environments can shape individual behavior (top-down effects), but also examines how individuals form groups or take actions that may affect higher level organizational or community spheres (bottom-up effects). The Centers for Disease Control and Prevention has incorporated social-ecological models into a number of its health promotion and disease prevention efforts. The simple onion or Russian doll rendering of social-ecological relations as concentric circles is not in itself very informative. However, flowchart models based on such relationships can be useful for specifying hypothesized cross-level influences. Read more