Sources are transformed into resources
Sources of minerals or water were altered by technology. Often technological change has caused these sources to be redefined as "resources," depending on the need of the tools being employed and the level of consumption required by the technology.
Resources, raw materials, or naturally formed and scattered materials that people use, transform or make into finished products are actually sources derived from the ecological systems found throughout the earth, oceans, or air.
Sources of biological wealth are inherent properties of ecosystems.
In this sense, Land, Air and Water form a potentially productive matrix [LAW ~ land + air + water ] from which subsistence, agricultural, industrial or advanced societies draw upon for their necessities.
Seen in this light the ecological core in the model is a reservoir of potential water -- energy -- air -- & land for use and preservation depending on these factors:
Impact equals Population • Affluence • Technology
Reserves and sinks are both important as repositories for times of shortage and as disposal (air and water sources) sites for unwanted, undervalued, or unappreciated materials.
Pacey, Meaning in Technology.
Pursell, White Heat.
Ann & Paul Ehrlich, The Dominant Animal.
Fritjof Capra, The Web of Life.