Environmental Engineering Reference
In-Depth Information
There is a difficult balancing act to perform when using local knowledge in for-
mulating and implementing conservation management. On the one hand, local
people understand their environment better than outsiders, at least on their terms.
Incorporating local knowledge can produce management strategies that are imple-
mentable, comprehensible and robust. On the other hand, and particularly when
the species of conservation concern are cryptic, rare and not the main target of
hunting, local knowledge may be lacking. Indices of abundance based on CPUE
or body condition can be very misleading; one only has to look at the number of
commercial fisheries collapses to appreciate this. It is tempting to suggest that these
indices are adequate for trends in relative abundance, if not for absolute abun-
dance, but this is not necessarily true either (Chapter 2). Local names for different
kinds of plant and animal are another area of difficulty—they don't always overlap
well with taxonomic species status, which is the important categorisation for con-
servation managers.
7.4.2.3 Cost-effectiveness
It is often assumed that monitoring ecological trends is an unalloyed good, and a
fundamental component of conservation. While it is impossible to make good
decisions from a position of ignorance, it is important to ask whether communities
are likely to want to invest time and effort in monitoring trends in their resources
(Box 7.5). It is also important to ask which type and level of monitoring will be
most cost-effective (i.e. which will give the best trade-off between the power to
Box 7.5
Monitoring crayfish—is it worthwhile?
Hockley
et al
. (2005) developed a framework for evaluating whether it is in com-
munities' interests to monitor their resources. They applied this to crayfish har-
vesting in Madagascar, using two types of monitoring—a mark-recapture study
over 5 days, and an abundance index based on the number of crayfish caught in a
single day. The abundance index produces population size estimates that are cor-
related to the mark-recapture estimates, but with far higher sampling error.
Hockley
et al
. estimate that in order to have an 80% chance of detecting a 30%
decline in the crayfish population, monitoring based on catch rates would have to
involve 12 visits a year to each of 20 sites—a massive investment of time (720 per-
son days per year). The mark-recapture method is much more sensitive—it is pos-
sible to achieve an 80% chance of detecting a 30% decline in the crayfish
population by sampling once a year in 10 sites (50 person days). However, the
mark-recapture estimate is substantially more complex to analyse, potentially
beyond the capabilities of local monitors.
The study village contained 25 harvesting families earning on average
US$0.76 per day from crayfish harvesting; a significant component of their
livelihoods (Figure 7.4). However, given this level of income, it is highly unlikely
