ABSTRACT
Ecosystems are complex thermodynamic systems that evolve in time. Thermodynamics is the study of energy. Energy is characterized by magnitude, form, and quality. While the concept of energy magnitude (e.g. calorie, joule, watt, horsepower) and energy form (e.g. kinetic energy, potential energy, chemical energy, heat transfer, work transfer) are introduced in elementary or high school, few are familiar with the concept of energy quality, especially its quantification. Energy quality measures the capacity of energy, in its various forms, to do useful work. Interestingly, it is the quality of energy that provides an explanation for the continued existence of life on earth (Edgerton 1982; Kay 1984; Schneider and Kay 1994), and hence the existence of ecosystems. That is, the quality aspect of energy makes it possible to obtain and maintain organization in the form of life from a soup of disordered basic atomic elements. Of more immediate interest, the study of energy quality has the potential to provide a quantitative method to characterize the status, maturity, or stage of development of ecosystems, and to provide fundamental physical explanations, at least, in part, as to survival strategies and structures employed within ecosystems as they evolve.
