2 Preliminary Considerations
Constancy and change of environmental conditions through time influence not only
ecosystem functioning, but also the development of human behaviour (Brim and
Kagan 1980). However, to date we do not have an overarching concept or reference
system that allows comparison between the histories of different regions with respect
to the magnitude of changing conditions, catastrophes, contingency and continuity.
Moreover, these terms are not clearly defined or separated, neither in science nor in
the non-scientific communication.
The considerations outlined here are based on the different preconditions and
assumptions that follow:
2.1 Definitions
Before establishing a tool for change in time with respect to species compositions,
distribution patterns of rare and threatened biota, and the risk of extinction, it is
necessary to clearly define related terms e.g., constancy, continuity, changing
conditions, contingency, periodicity, susceptibility, and catastrophe (see below).
2.2 Magnitude of Influence per Unit of Time
The impact of an influence on life, (the ecosystems and biota in a landscape or
region), relates to the magnitude of change, i.e. intensity of an influence. The lower
the size of the change, the lower the risk of consequences for life, or the need
for adjustment. Ecological extreme values in general have a higher impact than
average values. The focus on extreme values and events has led to a better understanding of ecological processes and conditions because extreme conditions have a
stronger influence on ecosystems and species compositions than mean conditions
(de Haan and Ferreira 2006). The mean temperature of Las Vegas, USA, for
example, is c. 19.2
C. This climate value does not say anything about the concrete,
normal or extreme temperatures during summer or winter time. However, particularly these matter and influence life. Mersa Matruh in Egypt has almost the same
average temperature (19.3
C). The absolute minimum temperature of Las Vegas
was measured as À13.3
C, in Mersa Matruh it was 1.4
C. Las Vegas knows frost,
Mersah Matruh does not.
Change: Risks and Predictability
183
Constancy and change of environmental conditions through time influence not only
ecosystem functioning, but also the development of human behaviour (Brim and
Kagan 1980). However, to date we do not have an overarching concept or reference
system that allows comparison between the histories of different regions with respect
to the magnitude of changing conditions, catastrophes, contingency and continuity.
Moreover, these terms are not clearly defined or separated, neither in science nor in
the non-scientific communication.
The considerations outlined here are based on the different preconditions and
assumptions that follow:
2.1 Definitions
Before establishing a tool for change in time with respect to species compositions,
distribution patterns of rare and threatened biota, and the risk of extinction, it is
necessary to clearly define related terms e.g., constancy, continuity, changing
conditions, contingency, periodicity, susceptibility, and catastrophe (see below).
2.2 Magnitude of Influence per Unit of Time
The impact of an influence on life, (the ecosystems and biota in a landscape or
region), relates to the magnitude of change, i.e. intensity of an influence. The lower
the size of the change, the lower the risk of consequences for life, or the need
for adjustment. Ecological extreme values in general have a higher impact than
average values. The focus on extreme values and events has led to a better understanding of ecological processes and conditions because extreme conditions have a
stronger influence on ecosystems and species compositions than mean conditions
(de Haan and Ferreira 2006). The mean temperature of Las Vegas, USA, for
example, is c. 19.2
C. This climate value does not say anything about the concrete,
normal or extreme temperatures during summer or winter time. However, particularly these matter and influence life. Mersa Matruh in Egypt has almost the same
average temperature (19.3
C). The absolute minimum temperature of Las Vegas
was measured as À13.3
C, in Mersa Matruh it was 1.4
C. Las Vegas knows frost,
Mersah Matruh does not.
Change: Risks and Predictability
183