Chapters 2-7 present the fundamental properties that explain typical ecosystem processes under "normal" growth and development and their responses to disturbance. These are:
(1) Ecosystems are open systems—open to energy, mass, and information. Openness is an absolute necessity because the maintenance of ecosystems far from thermody-namic equilibrium requires an input of energy. This core property is presented in Chapter 2.
(2) Ecosystems are ontically inaccessible—meaning that due to their enormous complexity it is impossible to accurately predict in all detail ecosystem behavior. It means that it is more appropriate to discuss the propensity of ecosystems to show a certain pattern or to discuss the direction of responses. This property is presented in Chapter 3.
(3) Ecosystems have directed development—meaning they change progressively to increase, in particular, feedback and autocatalysis. It is the observed direction of responses mentioned under point 2. This property is discussed in detail in Chapter 4.
(4) Ecosystems have network connectivity—which gives them new and emergent properties. The networks have synergistic properties, which are able to explain the cooperative integration of ecosystem components, which can at least sometimes yield unexpected system relations. This core property is covered in Chapter 5.
(5) Ecosystems are organized hierarchically—in the sense that we can understand one level only by understanding interactions with the levels below and above the scale of focus. Often major changes in one level are leveled out in the higher levels, where only minor hierarchical organization changes are observed. The properties associated with the are discussed in great detail by Allen and Starr (1982) in their book Hierarchy, Perspectives for Ecological Complexity and in the book A Hierarchical Concept of Ecosystems by O'Neill et al. (1986). The scaling theory and the allomet-ric principles are rooted in quantification of openness and are, therefore, presented in Chapter 2. The basic general elements of hierarchy theory are also presented in this chapter. Further examples of the application of hierarchy theory are presented in Chapters 3 and 7.
(6) Ecosystems grow and develop—they gain biomass and structure, enlarge their networks, and increase their information content. We can follow this growth and development using holistic metrics such as power, eco-exergy, and ascendency, respectively. For example, incoming solar radiation is first used to cover maintenance of the ecosystem far from thermodynamic equilibrium and afterwards used to move the system further from equilibrium, which increases the power, stored eco-exergy, and ascendency. This growth property is presented in Chapter 6. It is a core property because it explains how ecosystems develop and even evolve. Many ecosystem processes are rooted in the competition for the resources that are needed for growth and can be explained in this light.
(7) Ecosystems have complex response to disturbance—but when we understand properties of ecosystems such as adaptation, biodiversity, resistance, and connectedness, to mention a few of the most important properties covered in the book, we can explain and sometimes predict the responses of ecosystems to disturbances. This part of the ecosystem dynamics is presented in Chapter 7.
Chapters 2-7 are directed to answer first question above. The second question is answered throughout these chapters and summarized in Chapter 10, where the presented ecosystem theory is formulated by use of the seven properties and by formulation of ten propositions. The two formulations are completely consistent as discussed in this last chapter of the book.
The last question regarding the applicability of the presented theory to explain ecological observations and to be applied in environmental management is addressed in Chapters 8 and 9. The application of the theory in environmental management has been mostly limited to use of ecological indicators for ecosystem health assessment as described in Chapter 9. The theory has much wider applicability, but the use of ecological indicators has a direct link to ecosystem theory that facilitates testing the theory. Tests of the theory according to its applicability in practical environmental management and to explain ecological observations is crucial for the general acceptance of the ecosystem theory of course; but it does not exclude that it cannot be improved significantly. On the contrary, it is expected that the theory will be considerably improved by persistent and ongoing application because the weaknesses in the present theory will inevitably be uncovered as the number of case studies increases. Discovery of theoretical weaknesses will inspire improvements. Therefore. it is less important that the theory has flaws and lacks important elements than it is that it is sufficiently developed to be directly applied. We. the authors. are of the opinion that we do have an ecosystem theory today that is ready to be applied but which also inevitably will be developed significantly during the next one to two decades due to (hopefully) its wider application.
An ecosystem theory as the one presented in this book may be compared with geographical maps. We had already 2000 years ago geographical maps that could be applied to get an overview of where you would find towns. mountains. forests. etc. These maps were considerably improved and the geographical maps used in the 17th and 18th century were much more accurate and detailed. although they are of course not comparable with the satellite-based maps of today. Our ecosystem theory as presented today may be comparable with the geographical maps of the 18th century. They are. as the more than 200 years old geographical maps. very useful. but they can be improved considerably when new methods. additional information. and additional observations are available. It may take 20 or maybe 50 years before we have the quality of an ecosystem theory comparable with today's geographical maps. but the present level of our ecosystem theory is nevertheless suitable for immediate application. Only through this application we will discover new methods and demand for improvements. both theoretical and practical for science and management. ultimately leading to a more complete and accurate ecosystem theory.
The most fundamental parts of the presented ecosystem theory. particularly the more mathematical aspects. are placed in boxes. It makes it on one hand easy to find the theoretical elements of the entire ecosystem theory but it also facilitates reading for those preferring a less mathematical formulation of an ecosystem theory.
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