Ecosystems emerging: 2. Dissipation

Abstract This third paper in the series on Ecosystems Emerging deals with properties resulting from the second law of thermodynamics. Dissipation of energy and matter, which is degradation from more to less organized states, causes cycling of matter and origination of networks. The second law is presented in two forms: the classical one and by means of exergy which measures useful energy. Energy and matter dissipation condition the formation of structures, growth, development and evolution. In contrast to the ecological cliche that energy does not cycle in ecosystems, it becomes evident that energy must cycle like matter because the two are coupled. Matter cycling is necessary for the continued existence of ecosystems on earth because the closed planet has only a finite supply of material resources. Biological dissipation takes a variety of forms: respiration, excretion, egestion, natural and predatory mortality and others. Relations of dissipation by organisms to size and temperature are causes of similar relations for a number of life processes and also for certain ecological characteristics of organisms. This underlies the theory of ecosystem size and structure. Recognition of matter dissipation leads to substantial changes in ecological paradigms. For example, dissipation of nutrients can have positive effects on ecosystem production. Grazing mortality can speed primary production. Therefore, ecological studies must focus more on fluxes than standing biomasses. Detrital and microbial food paths play a significant role in ecosystems. The classical ideas of trophic pyramids and ecological efficiencies are changed completely by studies of dissipation. Dissipation of information relates to decreasing biodiversity and the present crisis of environment can be explained as a dissipation-driven entropy crisis.