Ecological indicators – Schrödinger Ratio

This article is a scientific overview of the Schrödinger ratio as a basic thermodynamic indicator, proposed by Howard Odum, inspired by the concept of Schrödinger that maintenance of a low-entropy structure depends on continuous inflow of low-entropy energy (or exergy inflow) and on exportation of high entropy. This is expressed as the ratio of the entropy-generation rate of the system to the entropy embodied in the structure. The ratio was conceived as an indicator of ecosystem development. We discuss two methods of calculating this ratio for ecosystems: (1) a case study applied to a forest, based on the so called R/B ratio, that is, the ratio of entropy generation by respiration to entropy content in biomass; (2) a more accurate procedure based on the ratio of two basic thermodynamic functions, entropy production and exergy. In ecosystems, the Schrödinger ratio is therefore also known as specific dissipation or the ratio of biological entropy production to the exergy stored in the living biomass. Case studies in the literature include lake ecosystems and their plankton community. A ratio comparing entropy production and information content in chemical and biological structures is also discussed as an analog of the Schrödinger ratio.