Systems and Ecosystems 5
• Tactical models, which are more empirical and are applied mainly in
specific instances, aiming at forecasting. They usually have a practical
purpose, are based on a large number of detailed hypotheses, have a
relatively narrow scope of application, and lead to quantitative conclusions, mainly of practical value.
• Strategic models, which are more abstract and general, which further
the investigation of basic mechanisms and causal relationships governing the functioning of the system, and whose main purpose is to
explain. They are usually theoretical in nature, contain fundamental
concepts, are based on a few simple hypotheses, are relatively broad
in scope, and lead more to qualitative conclusions.
These two categories of models constitute the two extremes of what is
essentially a continuous spectrum. Most of the models used in theoretical and practical research belong to some point on the spectrum—that is,
they show a mix of features of both categories, depending on the object of
study and the opportunities to approach the subject. Models always have
the following three properties:
• Generality, or applicability of the model to various situations
• Realism, or a degree of correspondence between the model’s logical
structure and the reality it is supposed to represent
• Precision, or the model’s ability to quantitatively reproduce the reality
through its results
A perfect model is a utopia. It is not possible to have a simultaneous
maximisation of generality, realism, and precision. Maximisation of these
three properties in the right combination determines the optimum use of
models, depending on the type and objective of the approach. To use the
example of ecological models, as a rule those usually used by biologists or
other laboratory scientists sacrifice generality for the sake of precision and
realism, whereas those proposed by scientists with a background in mathematics tend to sacrifice realism for the sake of generality and precision.
What is more, many theoretical ecologists believe that the models creating
the theoretical basis of ecology should not overstress precision but lay the
emphasis on generality and realism.
1.3 SyStEM StatE and Stability
System state is a fundamental concept. If we consider that the system is represented (that is, a complete image of it is formed) by n variables in a space
of n dimensions, then the total values of n variables at a certain moment in
time define the state of the system. The n variables change values over the
• Tactical models, which are more empirical and are applied mainly in
specific instances, aiming at forecasting. They usually have a practical
purpose, are based on a large number of detailed hypotheses, have a
relatively narrow scope of application, and lead to quantitative conclusions, mainly of practical value.
• Strategic models, which are more abstract and general, which further
the investigation of basic mechanisms and causal relationships governing the functioning of the system, and whose main purpose is to
explain. They are usually theoretical in nature, contain fundamental
concepts, are based on a few simple hypotheses, are relatively broad
in scope, and lead more to qualitative conclusions.
These two categories of models constitute the two extremes of what is
essentially a continuous spectrum. Most of the models used in theoretical and practical research belong to some point on the spectrum—that is,
they show a mix of features of both categories, depending on the object of
study and the opportunities to approach the subject. Models always have
the following three properties:
• Generality, or applicability of the model to various situations
• Realism, or a degree of correspondence between the model’s logical
structure and the reality it is supposed to represent
• Precision, or the model’s ability to quantitatively reproduce the reality
through its results
A perfect model is a utopia. It is not possible to have a simultaneous
maximisation of generality, realism, and precision. Maximisation of these
three properties in the right combination determines the optimum use of
models, depending on the type and objective of the approach. To use the
example of ecological models, as a rule those usually used by biologists or
other laboratory scientists sacrifice generality for the sake of precision and
realism, whereas those proposed by scientists with a background in mathematics tend to sacrifice realism for the sake of generality and precision.
What is more, many theoretical ecologists believe that the models creating
the theoretical basis of ecology should not overstress precision but lay the
emphasis on generality and realism.
1.3 SyStEM StatE and Stability
System state is a fundamental concept. If we consider that the system is represented (that is, a complete image of it is formed) by n variables in a space
of n dimensions, then the total values of n variables at a certain moment in
time define the state of the system. The n variables change values over the