Environmental Engineering Reference
In-Depth Information
Fig. 1.5 Simulation of an individual-based predator-prey model starts with a random initial
configuration (
left
).
Points
indicate the current positions of prey and predators; the line shows
the movement from the previous position.
Lighter shades
and
smaller points
represent the prey,
darker
and
larger ones
the predator. The spatial distribution is shown after 50 (
centre
) and 100
steps (
right
). Prey concentrate in dense clusters. For further model specification see Chap. 12
Structure Can Be Created by Blind Random Processes
Let us imagine individual prey, randomly moving in a habitat without any orienta-
tion. They regularly reproduce up to a population maximum. Predators move a bit
differently and follow a certain direction which is slightly changed stochastically at
each step (a detailed model description is given in Chap. 12). Let all individuals be
randomly dispersed in the beginning (Fig.
1.5
,
left
). Would you imagine finding all
prey closely aggregated in one or very few clusters after running the model for some
time? Chapter 12 discusses self-organizing phenomena like this in further detail.
Apparently, as illustrated with the model, spatial organization of organisms does
not need an underlying plan, or a pre-existing gradient. It just can emerge through
random interactions.
There are many more examples throughout this topic where elementary interac-
tions are specified, which bring up emergent phenomena and surprising results over
the long run. The discovery of how these phenomena relate to the underlying
interactions can make the construction of ecological models highly fascinating.
Comprehensive modelling and model networking also helps us to assess man-
agement and conservation options. You will find some interesting starting points to
follow these and comparable model applications for environmental conservation in
Chaps. 21 and 22.
1.3 Getting on: Diversity of Approaches in Ecological
Modelling
In ecological modelling, not all the approaches are genuine ecological develop-
ments. Ecological modelling is in the fortunate situation to be able to do “concept
(window-) shopping” in other fields of science. In fact, most of the methodologies
