232
l) Stability Properties In the Wadden Sea
(Un )predictability
In conjunction with "disturbance", reference is often made to "unpredictability"
(Costanza et al. 1993), which refers to a broad range of abiotic conditions, i.e. it is
not predictable how these conditions will change on small areas over short time
intervals. The complementary term "predictability" refers to a narrow range of
conditions and is therefore different from deterministic predictability. "Predictability" is a comparative concept which allows the abiotic conditions of different
ecological systems to be compared. For example, according to Costanza et al.
(1993), unpredictability is the key property of tidal zones and estuaries, whereas
forests and coral reefs are characterized by predictable conditions.
Emergent properties
"Emergent properties" are properties which only exist on certain levels of description, but not below this level. Resilience, for instance, can only be observed at the
level of populations or higher, since population resilience has no significance for a
single individual. The concept of emergent properties helps system properties be
explicitly defined and assessed. All too often in ecology people talk about "systems" without defining them, i.e. without stating explicitly the properties and interactions which are considered as essential to constitute the "system" (Jax et al.
1998; Grimm 1998). It should be noted that by "emergent properties" we do not
refer to unexplainable, "mystical" properties which cannot be studied scientifically
(cf. Wiegleb & Broring 1996; Muller et al. 1997).
Community and ecosystem
By "ecosystem" we will refer in the following to a landscape with all its abiotic
and biotic components, as well as the interactions between these components
(Chap. 2). This means in particular that we do not necessarily infer any emergent
property from the word "system". The same holds for "communities", which simply refers to different populations which occur in the same area at the same time.
9.3
A Canon of Questions
In the following we will discuss stability properties of those components of the
Waddens Sea which were studied by ELA W A T. Instead of components, it might
be more appropriate to talk of "ingredients": the ecosystem "Wadden Sea" is composed of different biotic and abiotic ingredients. As with a recipe, the properties of
each individual ingredient influence the properties of the system as a whole. Referring to "ingredients" is very apt because we take into account not just material
components and energy but also everything else which may more or less determine
the properties of the system as a whole. Therefore, not only nutrients and primary
production are considered, but also the presence or absence of certain species
(Jones et al. 1994), properties of the landscape (morphology, hydrography), of the
processes affecting the landscape (tides), and the entire disturbance regime.
l) Stability Properties In the Wadden Sea
(Un )predictability
In conjunction with "disturbance", reference is often made to "unpredictability"
(Costanza et al. 1993), which refers to a broad range of abiotic conditions, i.e. it is
not predictable how these conditions will change on small areas over short time
intervals. The complementary term "predictability" refers to a narrow range of
conditions and is therefore different from deterministic predictability. "Predictability" is a comparative concept which allows the abiotic conditions of different
ecological systems to be compared. For example, according to Costanza et al.
(1993), unpredictability is the key property of tidal zones and estuaries, whereas
forests and coral reefs are characterized by predictable conditions.
Emergent properties
"Emergent properties" are properties which only exist on certain levels of description, but not below this level. Resilience, for instance, can only be observed at the
level of populations or higher, since population resilience has no significance for a
single individual. The concept of emergent properties helps system properties be
explicitly defined and assessed. All too often in ecology people talk about "systems" without defining them, i.e. without stating explicitly the properties and interactions which are considered as essential to constitute the "system" (Jax et al.
1998; Grimm 1998). It should be noted that by "emergent properties" we do not
refer to unexplainable, "mystical" properties which cannot be studied scientifically
(cf. Wiegleb & Broring 1996; Muller et al. 1997).
Community and ecosystem
By "ecosystem" we will refer in the following to a landscape with all its abiotic
and biotic components, as well as the interactions between these components
(Chap. 2). This means in particular that we do not necessarily infer any emergent
property from the word "system". The same holds for "communities", which simply refers to different populations which occur in the same area at the same time.
9.3
A Canon of Questions
In the following we will discuss stability properties of those components of the
Waddens Sea which were studied by ELA W A T. Instead of components, it might
be more appropriate to talk of "ingredients": the ecosystem "Wadden Sea" is composed of different biotic and abiotic ingredients. As with a recipe, the properties of
each individual ingredient influence the properties of the system as a whole. Referring to "ingredients" is very apt because we take into account not just material
components and energy but also everything else which may more or less determine
the properties of the system as a whole. Therefore, not only nutrients and primary
production are considered, but also the presence or absence of certain species
(Jones et al. 1994), properties of the landscape (morphology, hydrography), of the
processes affecting the landscape (tides), and the entire disturbance regime.