Environmental Engineering Reference
In-Depth Information
compare methods for counting wildlife in Zimbabwe, which range from the expen-
sive and technically demanding (aerial surveys, vehicle surveys) to simple and
potentially locally implementable methods (counting duikers on foot or from bi-
cycles). The issues involved are that the faster you travel the more distance you cover,
so the more individual observations you can make and so the more precise your esti-
mate is likely to be (see Chapter 2). However, using a vehicle is costly and may cre-
ate disturbance, and hence bias counts. Gaidet-Drapier
et al
. also counted animals
at water points at the end of the dry season when water was very scarce—this is a
cheap and simple method of getting an estimate of population size, but has major
problems with bias (the animals coming to the water hole are an unknown propor-
tion of the population, even if probably a high proportion at that time of the year)
and is not amenable to statistical analysis. Weighing up the costs of sampling against
the efficiency of detection, the authors showed that bicycle counts were the most
cost-effective method for locally based monitoring.
To summarise the practical issues highlighted by these studies:
●
It is crucial to think about
cost-effectiveness
when planning monitoring—if
monitoring is not cost-effective it will not be sustainable.
●
Cost-effectiveness includes an analysis of the
power to detect change
—
cheap and simple monitoring may be a false economy because it produces
data with high levels of error which can't inform management in a meaning-
ful way (Katzner
et al
. 2007). It is important to do an analysis of the level and
type of monitoring that is required to detect population trends, and then see
whether this is realistic and affordable.
●
If the level of monitoring that is required to detect trends is more time-
consuming, expensive or technically difficult than the situation allows, then
there is a real question as to whether it is worthwhile to invest time, money
and community goodwill on it. This is where other solutions may be more
appropriate. Rather than using monitoring to reduce uncertainty, it may be
better to explicitly choose a management method that is
robust to uncer-
tainty
such as setting aside no-take areas (Chapter 6). So an active decision is
made to live with uncertainty about ecological trends, but to buffer against
uncertainty by using a precautionary management method.
The structure of decision-making is fundamental to the outcome of exploitation
(Table 7.2). At one extreme there are
open access
resources, with no overall control
on how people use the resource. This lack of institutional control is the basis for
Garrett Hardin's doom-ridden message that '
freedom in the commons brings ruin to
all
' (Hardin 1968). At the other extreme, the resource can be owned by an indi-
vidual or by the state, who, in theory at least, can control completely the use that is
made of it, and can manage for whatever objective they wish. The third type of
