Ecosystems emerging: 2. Dissipation

This third paper in the series on Ecosystems Emerging deals with properties resulting from the second law of thermodynamics.. Dissipation of energy an d matter, which is degradation from more to less organized states, causes c ycling of matter and origination of networks. The second law is presented i n two forms: the classical one and by means of exergy which measures useful energy. Energy and matter dissipation condition the formation of structure s, growth, development and evolution, In contrast to the ecological cliche that energy does not cycle in ecosystems, it becomes evident that energy mu st cycle like matter because the two are coupled. Matter cycling is necessa ry for the continued existence of ecosystems on earth because the closed pl anet has only a finite supply of material resources. Biological dissipation takes a variety of forms: respiration, excretion, egestion, natural and pr edatory mortality and others. Relations of dissipation by organisms to size and temperature are causes of similar relations for a number of life proce sses and also for certain ecological characteristics of organisms, This und erlies the theory of ecosystem size and structure. Recognition of matter di ssipation leads to substantial changes in ecological paradigms. For example , dissipation of nutrients can have positive effects on ecosystem productio n. Grazing mortality can speed primary production. Therefore, ecological st udies must focus more on fluxes than standing biomasses. Detrital and micro bial food paths play a significant role in ecosystems. The classical ideas of trophic pyramids and ecological efficiencies are changed completely by s tudies of dissipation. Dissipation of information relates to decreasing bio diversity and the present crisis of environment can be explained as a dissi pation-driven entropy crisis. (C) 1999 Elsevier Science B.V. All rights res erved.