Environmental Engineering Reference
In-Depth Information
where and for how long to harvest, the harvester weighs up the expected costs of
each option against the expected benefits (which may be monetary revenues, food
for the table, medicines or timber for building). The outcome of these harvester
decisions is the harvesting effort expended. The harvest mortality experienced by
an exploited population at a particular place and time is proportional to harvesting
effort, and this determines biological sustainability. This relationship is shown
in Figure 1.3.
One determinant of the stability of a bio-economic system is the institutional
structure—and particularly, who has control over harvesting. This determines how
backwards-bending the supply curve is, with a continuum between a sole owner
who doesn't discount the future (Figure 1.2(a)) and an open access system where
people don't consider the future in their harvesting decisions (Figure 1.2(b)).
Another determinant is the market structure—if the good has many substitutes,
then the demand curve will be nearly flat (Figure 1.2(a)), while if it is an irreplace-
able necessity it will be nearly vertical (Figure 1.2(b)), which may lead to big
changes in the level of population depletion for small changes in price.
There are five steps towards achieving sustainable use:
●
Objective setting—what do we wish to achieve with our intervention?
●
Data collection and analysis—what is the current situation?
●
Understanding—what factors affect sustainability?
●
Intervention—how can we move the system towards the desired state?
●
Maintenance—ongoing monitoring and adaptive management.
These steps are covered in the following chapters (Figure 1.4):
In
Chapter 2
we discuss the approaches that we can use to obtain biological data,
such as abundance, density and population structure. These data are fundamental
Collecting biological data
Chapter 2
Objective-setting
Chapter 7
Data analysis
Chapter 4
Collecting socio-economic
data
Chapter 3
Modelling
Chapter 5
Ongoing management
Chapter 7
Intervention
Chapter 6
Fig. 1.4
Schematic of the topic's contents by chapter.
