Jorgensen Fundamentals of Ecological Modelling

Applications in Environmental Management and Research
4. Auflage 2011
ISBN: 978-0-444-53568-9
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, Band Volume 21, 350 Seiten

Reihe: Developments in Environmental Modelling

Fundamentals of Ecological Modelling: Applications in Environmental Management and Research, Fourth Edition, provides a comprehensive discussion of the fundamental principles of ecological modeling. The first two editions of this book (published in 1986 and 1994) focused on the roots of the discipline the four main model types that dominated the field 30-40 years ago: (1) dynamic biogeochemical models; (2) population dynamic models; (3) ecotoxicological models; and (4) steady-state biogeochemical and energy models. The third edition focused on the mathematical formulations of ecological processes that are included in ecological models. This fourth edition uses the four model types previously listed as the foundation and expands the latest model developments in spatial models, structural dynamic models, and individual-based models. As these seven types of models are very different and require different considerations in the model development phase, a separate chapter is devoted to the development of each of the model types. Throughout the text, the examples given from the literature emphasize the application of models for environmental management and research. - Presents the most commonly used model types with a step-by-step outline of the modeling procedure used for each - Shows readers through an illustrated example of how to use each model in research and management settings - New edition is revised to include only essential theory with a focus on applications - Includes case studies, illustrations, and exercises (case study of an ecological problem with full illustration on how to solve the problem)

Autoren/Hrsg.

Jorgensen, S. E.

Leseproben

1 Introduction 1.1. Physical and Mathematical Models
Humans have always used models — defined as a simplified picture of reality — as tools to solve problems. The model will never be able to contain all the features of the real system, because then it would be the real system itself, but it is important that the model contains the characteristic features essential in the context of the problem to be solved or described. The philosophy behind the use of a model is best illustrated by an example. For many years we have used physical models of ships to determine the profile that gives a ship the smallest resistance in water. Such a model has the shape and the relative main dimensions of the real ship, but does not contain all the details such as the instrumentation, the layout of the cabins, and so forth. Such details are irrelevant to the objectives of that model. Other models of the ship serve other purposes: blueprints of the electrical wiring, layout of the various cabins, drawings of pipes, and so forth. Correspondingly, the ecological model we wish to use must contain the features that will help us solve the management or scientific problem at hand. An ecosystem is a much more complex system than a ship; it is a far more complicated matter to ascertain the main features of importance for an ecological problem. However, intense research during the last three decades has made it possible to set up many workable and applicable ecological models. Ecological models may also be compared with geographical maps (which are models, too). Different types of maps serve different purposes. There are maps for airplanes, ships, cars, railways, geologists, archaeologists, and so on. They are all different because they focus on different objects. Maps are also available in different scales according to application and underlying knowledge. Furthermore, a map never contains all of the details for a considered geographical area, because it would be irrelevant and distract from the main purpose of the map. If a map contained every detail, for instance, the positions of all cars at a given moment, then it would be rapidly invalidated as the cars move to new positions. Therefore, a map contains only the knowledge relevant for the user of the map, so there are different maps for different purposes. An ecological model focuses similarly on the objects of interest for a considered well-defined problem. It would disturb the main objectives of a model to include too many irrelevant details. There are many different ecological models of the same ecosystem, as the model version is selected according to the model goals. The model might be physical, such as the ship model used for the resistance measurements, which may be called microcosm, or it might be a mathematical model, which describes the main characteristics of the ecosystem and the related problems in mathematical terms. Physical models will be touched on only briefly in this book, which will instead focus entirely on the construction of mathematical ecological models. The field of ecological modelling has developed rapidly during the last 30 years due essentially to three factors: 1. The development of computer technology, which has enabled us to handle very complex mathematical systems. 2. A general understanding of environmental problems, including that a complete elimination of pollution is not feasible (denoted zero discharge). Instead, a proper pollution control with limited economical resources requires serious consideration of the influence of pollution impacts on ecosystems. 3. Our knowledge of environmental and ecological systems has increased significantly; in particular we have gained more knowledge of the quantitative relations in the ecosystems and between the ecological properties and the environmental factors. Models may be considered a synthesis of what we know about the ecosystem with reference to the considered problem in contrast to a statistical analysis, which only reveals the relationships between the data. A model is able to include our entire knowledge about the system such as: 1. Which components interact with which other components, for instance, that zooplankton grazes on phytoplankton 2. Our knowledge about the processes often formulated as mathematical equations, which have been shown to be generally valid 3. The importance of the processes with reference to the problem This is a list of a few examples of knowledge that may often be incorporated in an ecological model. It implies that a model can offer a deeper understanding of the system than a statistical analysis. Therefore, it is a stronger research tool that can result in a better management plan for solving an environmental problem. This does not mean that statistical analytical results are not applied in the development of models. On the contrary, models are built on all available knowledge, including that gained by statistical analyses of data, physical-chemical-ecological knowledge, the laws of nature, common sense, and so on. That is the advantage of modelling. 1.2. Models as a Management Tool
The idea behind the use of ecological management models is demonstrated in Figure 1.1. Urbanization and technological development have had an increasing impact on the environment. Energy and pollutants are released into ecosystems where they can cause more rapid growth of algae or bacteria, damage species, or alter the entire ecological structure. An ecosystem is extremely complex, therefore it is an overwhelming task to predict the environmental effects that such emissions may have. It is here that the model is introduced into the picture. With sound ecological knowledge, it is possible to extract the components and processes of the ecosystem involved in a specific pollution problem to form the basis of the ecological model (see also the discussion in Chapter 2, Section 2.3). As indicated in Figure 1.1, the resulting model can be used to select the environmental technology eliminating the emission most effectively. FIGURE 1.1 The environmental problems are rooted in the emissions resulting from industrialization and urbanization. Sound ecological knowledge is used to extract the components and processes of the ecosystem that are particularly involved in a specific pollution problem to form the ecological model applied in environmental management. Figure 1.1 represents the idea behind the introduction of ecological modelling, which has been a management tool since about 1970. Now environmental management is more complex and is applied to a wider spectrum of tools. Today we have alternatives and supplements to environmental technology such as cleaner technology, ecotechnology, environmental legislation, international agreements, and sustainable management plans. Ecotechnology is mainly applied to solve the problems of nonpoint or diffuse pollution often originated from agriculture. The significance of nonpoint pollution was hardly acknowledged before 1980. Furthermore, the global environmental problems play a more important role today than 20 or 30 years ago; for instance, the reduction of the ozone layer and the climatic changes due to the greenhouse effect. The global problems cannot be solved without international agreements and plans. Figure 1.2 attempts to illustrate the current complex picture of environmental management. FIGURE 1.2 The idea behind the use of environmental models in environmental management. Environmental management today is very complex and must apply environmental technology, alternative technology, and ecological engineering or ecotechnology. In addition, the global environmental problems play an increasing role. Environmental models are used to select environmental technology, environmental legislation, and ecological engineering. 1.3. Models as a Research Tool
Models are widely used instruments in science. Scientists often use physical models to carry out experiments in situ or in the laboratory to eliminate disturbance from processes irrelevant to an investigation: Thermostatic chambers are used to measure algal growth as a function of nutrient concentrations, sediment cores are examined in the laboratory to investigate sediment-water interactions without disturbance from other ecosystems components, reaction chambers are used to find reaction rates for chemical processes, and so on. Mathematical models are widely applied in science as well. For example, Newton’s laws are just relatively simple mathematical models of the influence of gravity on bodies, but they do not account for frictional forces, influence of wind, and so forth. Ecological models do not differ essentially from other scientific models except in their complexity, as many models used in nuclear physics may be even more complex than ecological models. The application of models in ecology is almost compulsory if we want to understand the function of such a complex system as an ecosystem. It is simply not possible to survey the many components and their reactions in an ecosystem without the use of a model as holistic tool. The reactions of the system might not necessarily be the sum of all the individual reactions, which implies that the properties of the...