Systems ecology is not a hypermathematical, abstract study for specialists only. It does not require precise, well-quantified observations any more than any other scientific pursuit. In fact, systems ecology does quite well with qualitative data alone. One of the aims of systems ecology is to incorporate in a logical structure, as much of a scientist´s intuition and ´feel´ for an ecosystem as possible. Systems ecology is an attempt to merge the mathematical rigor and predictive power of general systems theory, and its associated tools from operations research and engineering, with the knowledge base of natural history and ecology.
General systems theory is a science that studies the abstract properties of systems. It attempts to find the commonality in things as diverse as atomic particles, ecosystems, and political parties. The basic ideas were proposed in the 1940´s and 50´s by Ashby (1961), von Bertalanffy (1969), and others. They felt that the same techniques of interdisciplinary teamwork and mathematical analysis that had worked so well during World War II to produce weapons of destruction, could help solve problems of health, starvation and social unrest as well (Miser 1980). Their idea was that whenever objects interact, they must do so in certain well-defined ways. Study of new systems of objects should involve a determining which pattern of interaction the new system uses. It was hoped that patterns of interaction would be fairly limited so that they could be cataloged and studied as such. Except in certain narrowly defined fields (for example, queuing theory), this has not come to pass, although attempts have been made to produce such catalogs (Miller 1978). General Systems Theory, while not yet succeeding in its ultimate goal, does offer a great deal to ecologists and natural resource managers:
- a structured world-view;
- a structured approach to problem solving;
- a theory of conceivable system behaviors; and
- a set of powerful techniques for analyzing system behaviors.
Ecology is only a little older than General Systems Theory, starting at the end of the nineteenth century. Tansley (1935) introduced the term ´ecosystem,´ but the concept is much older. Möbius (1877) wrote about an oyster reef as a ´biocoenosis,´ and Forbes (1887) wrote about a lake as a ´microcosm.´ Ecology is the science of the interactions between organisms and their environment (Odum 1971, Miller 1979).
Despite over half a century of trying, it has not developed much beyond the stage of description. Many of the ´principles´ laid down by Odum and others in the early fifties are now being questioned. The strength of ecology still comes from its roots in Natural History, which goes back much further than 100 years. Ecology offers:
- a wealth of descriptive natural history data,
- extremely complex interactions,
- a conceptual framework (ecosystem – community – population – individual).
The synthesis of these two sciences is called systems ecology. A systems ecologist is interested in interactions, and in whole system behavior. Mathematics often is involved, but the approach and attitude are more important than the tools. Science, including ecology, has tended to concentrate on small well-defined problems. Reductionism has been the rule. But General Systems Theory and systems ecology attempt to study systems as such, for example, organisms within their environment. Systems ecology involves:
- constructing conceptual models of ecosystems;
- statistical manipulation of data;
- building dynamic models of ecosystems;
- computer simulation;
- applying systems analysis techniques to ecosystem models;
- using all of the above to formulate new hypotheses and tests for hypotheses in the field.
1.1 Sects in Systems Ecology
A large number of approaches have already developed within ´systems ecology.´ Unfortunately, these various schools or sects are often on unfriendly terms, or at best seldom communicate with one another. The development of these sects was probably inevitable due to the diverse backgrounds of the scientists in the field, and due to the lack of firm laws in ecology. However, it should become apparent that all of these approaches have good points, and one should not scorn any of them. Ecosystems are too diverse, and ecologists are too small in number and too ignorant for any one group to have videos pornos gratis all the truth.
1.1.1 Population-evolution approach
This sect uses Lotka-Volterra equations applied to communities. Important concepts include K- and r-selection, island biogeography, and competition or predation as organizing features of biological communities. Key practitioners include Robert MacArthur, Richard Levins, G. Evelyn Hutchinson, Eric Pianka, etc. (Cody and Diamond 1975, Hutchinson 1978). Most likely to be published in American Naturalist.
1.1.2 Theoretical/Biomathematical Approach
This group uses simple equations to get mathematically tractable results and intuitive insights. Often optimization or optimal control is involved. Practitioners include John Maynard-Smith and Robert May. Mathematical Biosciences and American Naturalist are typical journals.
1.1.3 Big Biology – Simulation Approach
Make big, complicated differential (or difference) equation models of big, complicated systems. The model forms the focal point of a large interdisciplinary team of researchers. The International Biological Program (IBP) spawned a number of these efforts, some of which are continuing today. Practitioners include Scott Overton, George VanDyne, George Innis and the Oak Ridge group.
1.1.4 Statistical-Manipulation-of-Data Approach
Take big data sets, such as those generated by the IBP, and apply factor analysis, principal components analysis, multivariate regression, etc. to gain insight into ecosystems, or to answer specific questions. Practitioners include K. E. F. Watt, and T. F. H. Allen.
1.1.5 Systems Dynamics Approach
Based on modeling work of Forrester and Meadows of MIT. This group produced the first world model (Meadows et al. 1972), developed the DYNAMO computer simulation language, and a unique method of diagramming conceptual models (Forrester diagrams). They publish books through the Wright-Allen Press (Forrester 1961, 1969, 1971), and publish in engineering journals primarily. Key practitioners in the ecology arena are Dennis Meadows (now at Dartmouth), and ? Fey (at Georgia Tech).
1.1.6 Linear Modeling and Systems Analysis
Attempt to use the mathematical power of linear systems theory and systems analysis techniques to model the major processes of ecosystems. Major practitioners include B. C. Patten, the Oak Ridge group, Patten´s students (including me), and R. Mulholland. Publish in Ecological Modelling.
1.1.7 Energy Flow Analysis
This is a group of ecologists who believe that energy is the common currency of all systems. By analyzing energy flow in both natural and man-made systems, they hope to discern much of the behavior of these systems (Odum 1983). H. T. Odum and his students are the principal members of this group.
1.1.8 Management Modelers
This is a diverse group of people who use whatever technique they can to solve a problem presented to them in management of wildlife populations, parks, conservation preserves, etc. The driving principles here are to produce results that will improve management decisions. Practicioners include Mangel, Clark, Starfield, Bleloch, and others.
1.2 What is a Model?
Models come in many different forms, many of which we do not usually think of as models. Language itself is a model, allowing us to associate abstract concepts with labels (words), a set of rules for stringing words together (grammar), and allowing us to build models of reality. Some languages lack the tools necessary to express certain realities that we might want to express. Some languages allow complex expression of the status quo, but do not provide for dynamics. Because of the range of models, it is difficult to come up with a definition that fits them all. However, the following definition will suffice: A model is a simplification of reality that retains enough aspects of the original system to make it useful to the modeler.Models may take many forms.