The properties of ecosystems can only be revealed by the use of a pluralistic view. It is therefore not surprising that there are a few different ecosystem theories published in the scientific literature. It is on the other hand necessary to try to unite the theories and examine if they are tied up in contradictions or form a pattern that can be used to give a better understanding of the nature of ecosystems and to solve the global environmental problems. The goal is to give a common framework of reference for further development of a more profound and comprehensive ecosystem theory than the one we are able to present today. The pattern should serve as a "conceptual diagram'', which can be used as the basis for further discussion of how ecosystems behave.
We are still in an early stage of an ecosystem-theoretical development and it may be argued that this attempt is premature, but the experience from modelling has taught us that it is better to conclude one's thoughts in a conceptual diagram at an early stage and then be ready to make changes than to let all modelling efforts wait until all details are known, as this will never be the case due to the immense complexity of nature (J0rgensen, 2002). Moreover, recent development in ecosystem theory has made it possible to conclude that the theories presented here are indeed consistent and supplementary. This recent development will be presented in this section and Section 1.12.
The centre of the presented pattern below is the tentative fourth law of thermodynamics or ecological law of thermodynamics (ELT), but it cannot be excluded that other formulation of this law could be the core of an ecosystem theory. What can we conclude from this (tentative) law about ecosystem properties? Can we, as it is known from physics, formulate a limited number of laws and explain a very large number of observations (J0rgensen, 2002; J0rgensen and Svirezhev, 2004)? This question has been answered with a clear "yes" in this volume. The recent development in system ecology represents a paradigm shift. The paradigm that is now receding has dominated our culture for several hundred years. It views the universe as a mechanical system composed of elementary building blocks. The new paradigm is based on a holistic world view. The world is seen as an integrated whole and recognizes the fundamental interdependence of all phenomena.
The tentative ecological law of thermodynamics (ELT) gives information on which of the many possible processes will be realized as a result of a competition among more possibilities, than the flow of exergy can accomplish. Ulanowicz (1997) has introduced the expression "the propensity of ecosystems'' to stress that ecosystems and their forcing functions encompass many random components and they have an enormous complexity which makes accurate predictions impossible. Propensities are weighted or conditional probabilities that are inherent features of changing situations or occasions rather than absolute properties of relational processes and components. Ever since the quantum mechanics introduced indeterminacy, it has become increasingly easy to recognize that we do actually live in a world of propensities, with an unfolding process of realizing possibilities and creating new possibilities. It seems therefore advantageous to include this expression in the formulation of the pattern of ecosystem theories, and also in the formulation of the tentative fourth law of thermodynamics.
The tentative law asserts therefore, according to the latest formulation, that: A system that receives a through-flow of exergy (high-quality energy) will try to utilize the exergy flow to move away from thermodynamic equilibrium, and if more combinations of components and processes are offered to utilize the exergy flow, the system will select the organization that gives the system as much exergy content (storage) as possible, that is maximizes dEx/dt.
A few very competent ecologists have expressed preference for a formulation where the flow of exergy is replaced by a flow of free energy, which of course is fully acceptable and makes the formulation closer to classic thermodynamics. However, eco-exergy can hardly be replaced by free energy because it is a free energy difference between the system and the same system at thermodynamic equilibrium. The reference state is therefore different from ecosystem to ecosystem, which is considered in the definition of eco-exergy. In addition, free energy is not a state function far from thermodynamic equilibrium—just consider the immediate loss of eco-exergy when an organism dies. Before death the organism has high eco-exergy because it can utilize the enormous information that is embodied in the amino acid sequence of the enzymes, which are controlling the life processes. At death the organism looses immediately the ability to use this information, which therefore becomes worthless. The role of information in the evolution will be further discussed in Chapter 2.
The support for the validity of the tentative law in its present formulation is strong and may be summarized in the following three points:
1. It may be considered a translation of Darwin's theory to thermodynamics and is consistent with the basic, thermodynamic laws. The selected organization is the one which offers most "survival" that can be measured as exergy. The selection is in accordance with the latest formulations of Darwin's theory still taking place on the levels of species. The species are surviving, growing and fighting for the resources. All the species are, however, connected in an ecological, cooperative, synergistic network and are dependent on each other. The survival is under the prevailing conditions, which include the presence of all the components in the ecological network. All the species in the ecological network are influencing all the other species. The result is therefore that the entire ecological network gets as much survival and therefore eco-exergy as possible under the prevailing conditions.
2. The application of the hypothetical law in models gives (many) results that are consistent with ecological observations (see J0rgensen, 2002; J0rgensen and Svirezhev, 2004).
3. Many ecological observations can be explained by the presented hypothesis (see J0rgensen et al., 2000; J0rgensen, 2002; J0rgensen and Svirezhev, 2004; J0rgensen et al., 2007).
Below are presented a few case studies from J0rgensen (1997, 2002) and J0rgensen et al. (2000) supporting the presented exergy storage hypothesis, but maximum power or ascendency could also have been applied. More examples can be found in the above-given references.
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