Environmental Engineering Reference
In-Depth Information
expenditure on the preservation of endangered species. Several empirical
CVM studies have been used to determine values related to the conserva-
tion of individual and endangered species in protected areas (Stoll and
Johnson, 1984; Brown and Henry, 1993). Research on endangered or
threatened species includes the value of preserving the whooping crane
(
Grus americana
)
population at the Arkansas National Wildlife Refuge
in Texas for viewers and non-viewers (Bowker and Stoll, 1988) at about
US$6 per person per year. Similarly, Boyle and Bishop (1987) estimated
the value of preserving the bald eagle at US$17.46 per person per year.
A study conducted by Brown et al. (1994) values the northern spotted
owl and its ancient old growth forest habitat using the contingent ranking
approach. In this study, respondents were of ered i ve dif erent policies.
Associated with each policy were the cost of the policy, the area preserved,
the estimated number of owl pairs preserved and their probability of sur-
vival. They estimated existence values for conserving the northern spotted
owl at about US$20 per person per year. Probabilistic theoretical models
have been used to determine the benei ts of important wildlife species
such as the northern spotted owl in old naturally regenerated redwood
forests and have demonstrated the high marginal cost of preservation
(Montgomery et al., 1994). Estimates based on the probability of survival
and a reduction in timber stumpage supply give an estimated welfare cost
of US$21 billion to ensure an 82 per cent chance of the species surviving.
Increasing the chance of survival from say 90 per cent to 95 per cent was
estimated to cost an additional US$13 billion.
Indirect use values and ecosystem function
Much of the discussion in the second section of this chapter dealt with
the properties of ecosystems including their productivity, resilience and
stability. There is a signii cant literature on the value of ecosystem services
including indirect values (Ellis and Fisher, 1987; Barbier, 1994; Bell, 1997;
Daily, 1997; Barbier, 2000; Daily et al., 2000). Indirect values associated
with biodiversity can be measured using surrogate market approaches
using the production function approach. Information about a marketed
good (timber, crops or livestock sales) is used to infer the value of a related
non-marketed good (for example, forest, agricultural or wetland habitat).
The basic assumption underlying this approach is that, if, for instance,
biodiversity supports agricultural or forest production, then this ecologi-
cal service provides an additional environmental input into the agricul-
tural or forest enterprise.
For example, the stability of a managed ecosystem constitutes an indi-
rect use value and represents an important function to land managers.
As seen above, biodiversity may mitigate large inter-annual variation in
