Ecological models purpose

If ecological modeling is to become a standard tool for risk assessments of pesticides, all stakeholders involved need to understand what models are and how they are developed. It is important to realize that models by definition ignore many, if not most, aspects of real systems in order to identify key factors of the system s internal organization. Models are based on assumptions that are implemented, tested, and revised. Model development is iterative and ends when certain acceptance criteria are fulfilled. To assess or evaluate a model, we need to know its purpose. 

The building of reaction models is directed towards two goals (i) to simulate chemical processes of practical interest (industrial, ecological, biological, etc.) (ii) to analyze rate data in order to elucidate reaction mechanisms and to determine fundamental kinetic parameters. Of course, the results of fundamental studies can in turn be used for simulation purposes. 

These research programmes involve the housefly, Musca domestica, and the tobacco whitefly, Bemisia tabaci. Both are based in the laboratory in the firm belief that for these and many other pests, much of the data needed for such descriptive modelling can be collected more quickly and with greater precision under laboratory conditions than in the field. There is, however, a very important proviso to this statement, since for laboratory experiments to be of direct practical relevance they must simulate closely both the ecology and control of insects under field conditions (.7). The purpose of this paper is to outline the philosophy and objectives of these two programmes and to highlight some achievements to date. 

For ecological applications like pesticide risk assessment, we have to find ways to avoid ad hoc choices of model types and ad hoc design of the models themselves. As for the choice of model type, it is important that managers understand the strength and weaknesses of different model types so that they formulate the purpose of the model as precisely and detailed as possible. Part of the specification of the model s purpose is also a detailed specification of the acceptance criteria of the model (Bart 1995) What kind of evidence is required to show that a model has been verified and validated ... 

We focus on a version of the CTRW model adapted for the description of plant invasions. Further modifications of the model for applications to animal invasions or more complex situations are straightforward. Although these models are rather complex at first sight, the results and expressions in most cases are simple and have a clear ecological meaning. This makes the models attractive tools for management purposes. One of our main results consists of a threshold condition to predict if a species will show invasive behavior or not in terms of their specific life cycle. This... 

Estimation of ecological efficiency of national transport system requires formal model of this system to represent its complexity and its features significant for the purpose of research (Jacyna 2012). 

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