22/\
Y Stahilny Properties 111 the Wadden Sea
The same questions will be posed in connection with each component: How
does the assessment of stability properties depend on the scale of observation (both
spatial and temporal), on the type of disturbance, on the variable of interest being
considered, and on the definition of the reference dynamics? This will grant insights which extend beyond individual components and which refer to the processes in the Wadden Sea which are generally essential for stability properties.
However, deterministic predictions are impossible because of the openness and
complexity of ecological systems, and in particular due to the unpredictability of
individual events which may shape ecosystems to a large degree.
In the past, attempts to assess stability properties of ecological systems were
often linked or even equated to the notion that ecological systems are entirely
regulated, with the "natural" state being an equilibrium (cf. Reise 1990b). Here we
use stability concepts in a different way, without connotations such as "regulation"
or "equilibrium". We consider assessments of stability properties as a diagnostic
tool which helps organize our thinking about properties and processes of the Wadden Sea (Chaps. 2 and 10). A diagnostic tool must not be confused with an entirely
objective device. Diagnoses are necessarily subjective to some degree: they are an
attempt to integrate and interpret measurements and observations. Interpretations,
however, are not only intluenced by experience and knowledge, but possibly also
by prejudices. The enumeration of stability properties presented in this chapter is
thus not "objective" in the way that, for example, hard data are; nevertheless it is
still "scientific" in the sense of a scientific discussion.
Interpreting stability concepts as diagnostic tools also means that we consider
general assessments of the "stability" or resilience of an entire ecosystem to be
impossible (Grimm 1996; Gigon & Grimm 1997; Grimm & Wissel 1997). "Stability", like the concepts "energy" and "information", represents the hope of many
ecologists for "a global explanatory power ... which makes tedious work with details more or less supertluous. This hope failed as a rule." (Schwegler 1985,
p.263).
In the following we will first define and explain the conceptual framework that
we used for our synthesis of the ELA W AT project. Then we will discuss stability
properties and their underlying mechanisms for all the components of the Wadden
Sea studied by ELA WA T. Finally, we will summarize these mechanisms for the
species living in the Wadden Sea.
9.2
The Conceptual Framework: A Glossary
The conceptual framework of ELA W AT and its development are explained in
Chap. 2. Below, we compile a list of the concepts which are most important for the
synthesis of the ELA W AT project and briefly explain them in more detail, as a
clear synthesis is only possible with clearly defined concepts.
Stability
"Stability" as an individual, isolated term has become completely useless in ecology because it is impossible to assign a single, precise meaning to this term
Y Stahilny Properties 111 the Wadden Sea
The same questions will be posed in connection with each component: How
does the assessment of stability properties depend on the scale of observation (both
spatial and temporal), on the type of disturbance, on the variable of interest being
considered, and on the definition of the reference dynamics? This will grant insights which extend beyond individual components and which refer to the processes in the Wadden Sea which are generally essential for stability properties.
However, deterministic predictions are impossible because of the openness and
complexity of ecological systems, and in particular due to the unpredictability of
individual events which may shape ecosystems to a large degree.
In the past, attempts to assess stability properties of ecological systems were
often linked or even equated to the notion that ecological systems are entirely
regulated, with the "natural" state being an equilibrium (cf. Reise 1990b). Here we
use stability concepts in a different way, without connotations such as "regulation"
or "equilibrium". We consider assessments of stability properties as a diagnostic
tool which helps organize our thinking about properties and processes of the Wadden Sea (Chaps. 2 and 10). A diagnostic tool must not be confused with an entirely
objective device. Diagnoses are necessarily subjective to some degree: they are an
attempt to integrate and interpret measurements and observations. Interpretations,
however, are not only intluenced by experience and knowledge, but possibly also
by prejudices. The enumeration of stability properties presented in this chapter is
thus not "objective" in the way that, for example, hard data are; nevertheless it is
still "scientific" in the sense of a scientific discussion.
Interpreting stability concepts as diagnostic tools also means that we consider
general assessments of the "stability" or resilience of an entire ecosystem to be
impossible (Grimm 1996; Gigon & Grimm 1997; Grimm & Wissel 1997). "Stability", like the concepts "energy" and "information", represents the hope of many
ecologists for "a global explanatory power ... which makes tedious work with details more or less supertluous. This hope failed as a rule." (Schwegler 1985,
p.263).
In the following we will first define and explain the conceptual framework that
we used for our synthesis of the ELA W AT project. Then we will discuss stability
properties and their underlying mechanisms for all the components of the Wadden
Sea studied by ELA WA T. Finally, we will summarize these mechanisms for the
species living in the Wadden Sea.
9.2
The Conceptual Framework: A Glossary
The conceptual framework of ELA W AT and its development are explained in
Chap. 2. Below, we compile a list of the concepts which are most important for the
synthesis of the ELA W AT project and briefly explain them in more detail, as a
clear synthesis is only possible with clearly defined concepts.
Stability
"Stability" as an individual, isolated term has become completely useless in ecology because it is impossible to assign a single, precise meaning to this term