Environmental Engineering Reference
In-Depth Information
Harvesting system
Environmental
variation/change
Population dynamics
Resource stocks
Resource users
Socio-economic-
political
variation/change
Harvesting
Data
Management rules
Policy-making
Management system
Fig. 7.5
A simplified representation of system dynamics. The crucial thing to note
is that we cannot just consider the resource itself, nor even the resource and the
harvesters—we need to understand the dynamics of management as well.
7.5.2.3 Modelling the system
Uncertainty
A fundamental component of modelling system dynamics is the way we treat
uncertainty.
Every component of Figure 7.5 is subject to uncertainty, and this
needs to be quantified. People categorise uncertainty in many ways. However, the
main types are:
●
Process uncertainty
. This is the most widely recognised type of uncertainty,
and is generated by the fact that nature is inherently variable. There is vari-
ation in climate from year to year, chance events may raise or lower mortality
or birth rates. If animals are not evenly distributed, people's harvest levels will
vary depending on whether they come across a prey group or not. This type of
uncertainty is reflected in the variability of the data collected in monitoring
and can be addressed in data analysis using statistical techniques, and in
