realistic in most economic models) halves the value of all future harvests. Severe dis-
counting can therefore change the attractiveness of sustainable resource utilization
for commercial interests.
Biologically, the rational scheme for harvesting is to reduce the population to a
density allowing a suitable sustained yield and then take any excess population recruit-
ment that accrues thereafter, via either harvesting a constant proportion of the popu-
lation or maintaining a constant escapement at this target. But this biologically
sustainable strategy does not necessarily maximize economic gain. Colin Clark’s (1976,
1990) superb treatise on the economics of harvesting natural resources shows unam-
biguously that the best biological strategy and the best economic strategy coincide
only when a population’s maximum rate of increase greatly exceeds the discount rate.
Rabbits and herrings go into that category. When maximum rate of population increase
is lower than the discounting rate, however, the real money is made more by cap-
ital reduction than by sustained yield. It may even be economically clear-sighted to
make a total trade-off, taking all revenue by capital reduction and sacrificing all future
sustained yield. This strategy maximizes net revenue, discounted to present value,
when the population’s maximum rate of increase is below about 5% per year. This
can be the economic justification for the extinction of a slow-growing population
(and maybe even a species). Blue whales and redwood trees are obvious examples of
such slow-growing organisms, as would be many threatened or endangered species.
In such cases, economic incentives clearly cannot be relied upon to serve the greater
good.
Discounted valuation of future profits is more likely for a privately owned renew-
able resource. This should be less likely for a publicly owned resource, because the
public’s discount rate should be much lower. Indeed, one could argue that environ-
mental stewardship argues against any discounting at all, on purely ethical grounds.
Publicly owned resources can sometimes take on the character of privately owned
resources, however, when the people managing the resource and the people harvesting
the resource imagine that they, and not the people as a whole, own the resource.
Any scheme to harvest a publicly owned renewable resource necessarily involves
three parties: the owners of the resource (the people), the harvester of the resource
(usually a private company), and the manager of the resource (a government agency)
that regulates the harvesting. According to constitutional theory, the people in the
agency are supposed to act for the owners of the resource, but often they become
locked into a symbiotic relationship with the harvesters as if those two groups were
themselves joint owners of the resource. Technical advice on sustainable yield
offered by the agency’s own research branch is commonly ignored by its policy and
planning branch when it conflicts with the short-term requirements of the industry.
Thus, the ecological aberrations that necessarily follow from the economic implica-
tions of the discount rate, and against which the people in the managing agency are
employed to guard, often dominate the harvesting operation. Forestry and fisheries
provide numerous examples, and commercial wildlife harvesting is not necessarily
immune.
The way in which a safe sustained yield is estimated depends on the population’s
growth pattern that, in turn, is determined by the relationship between the popula-
tion and its resources. The yield can be estimated in terms of either a numerical off-
take or an appropriate harvesting proportion. The consequences of any harvesting
WILDLIFE HARVESTING 353
19.10 Summary
