The science of ecology entails an examination of nature in all its interconnected complexity. Human ecology, on the other hand, has a strong anthropocentric emphasis and is concerned more directly with man’s interaction with the natural system. It is an integrative approach for looking at the world’s economic system and the natural environment upon which it depends in the context of sustainability. Human ecology holds that one cannot understand either the economy or the environment without assessing the impact of each upon the other. A problem for analyses that link resource-based economic, environmental, and ecological considerations is the absence of a common numeraire. However, a procedure called natural capital accounting (NCA) has been used to model an economy using an embodied energy numeraire.
