Prior to performing a regional sustainability assessment study, one should define what sustainability or sustainable development means. One definition for sustainable development given by World Commission on Environment and Development (WCED) in 1987 is “development that meets the needs of the present without compromising the ability of future generations to meet their own needs” (WCED, 1987). This definition is vague in terms of foreseeing what the needs of future generations will be and how the current needs will be met without compromising an unknown future (Marshall & Toffel, 2005). The vagueness in this definition of sustainability is also due to lack of unanimity in defining what is regarded as sustainable. To Costanza and Patten (1995), sustainability is not a “definition”, but a “prediction” problem. One can only determine a system as sustainable after seeing the results for certain. In that regard, to better objectify the sustainability concept, the “time and space scales” should be specified regarding what is considered as sustainable and unsustainable (Costanza & Patten, 1995). In nature, systems are interconnected within a hierarchical order through energy and material exchanges (Odum, 1996).