Environmental Engineering Reference
In-Depth Information
in the country's oil boom, demand for bushmeat and fresh fish is likely to go up,
with potential consequences for sustainability (East
et al
. 2005, Box 6.1).
There's no reason why demand curves for wildlife products should differ from
other economic goods—but supply curves are very different. Because the relation-
ship between a population's productivity, in terms of the number of new individual
produced, and its size is dome-shaped (Figure 1.1(b)), the quantity supplied only
increases with increased price up to the MSY level. After that, although higher
prices lead to more effort being put in, that effort yields less and less because the
population is depleted (Figure 1.1(c)). Using the simple logistic model, this trans-
lates into a backwards-bending supply curve in situations where there is no control
over resource use. As Figure 1.2(b) demonstrates, the combination of an inelastic
demand curve and a backwards-bending supply curve can potentially be very
destabilising (Clark 1990).
Harvesting systems are bio-economic. The population dynamics of the exploited
species interact with the incentives that harvester households are experiencing to
determine the costs of hunting (both opportunity costs and direct costs; Section
3.2.5.1), and these costs determine the supply curve. When deciding whether,
Incomes
Habitat loss
Governance
Alternatives (producers)
Alternatives (consumers)
External factors
Consumer
demand
Hunter
costs
Biology
Sustainability
Indicators
CPUE
Effort
Fig. 1.3
The bioeconomic harvesting system. The relationship between price and
hunter cost determines hunter effort, which determines prey population size and
structure, which feeds back into hunter costs. This is a dynamic system. Price is a
function of consumer demand, and external factors affect the system—demand
may be affected by alternative foodstuffs, hunter costs by alternative livelihood
activities, prey by habitat destruction and everything by the institutional and
governance structures that the system sits within (laws, traditions, etc). An example
of a sustainability indicator, catch per unit effort, is given.
