Environmental Engineering Reference
In-Depth Information
use value is the same as that outlined above and includes, for example,
harvesting timber from a forest or the use of recreation services provided
by a national park. Indirect use value on the other hand refers to the life
support services provided by ecosystems. These include ecosystem func-
tions such as l ood control, catchment protection, nutrient cycling and
carbon sequestration. The biological diversity of managed landscapes may
serve an important role in maintaining ecosystem functions and thus serve
to support the productive process.
Measuring biodiversity values
Early studies on wildlife values employed revealed preference methods,
such as the so-called travel cost method (TCM). This technique was i rst
proposed for use in recreation studies and was subsequently rei ned and
applied in empirical studies by Clawson and Knetsch (1966). The method
is based on the premise that it should be possible to infer values placed by
visitors on environmental outdoor recreation services from the costs that
they have incurred in order to experience these sites. Such costs include
costs associated with travelling to a recreation site and the imputed value
of people's time. A statistical relationship between observed visits and the
cost of visiting a site is determined. This is then used to construct a demand
curve from which consumer surplus can be measured. The current value of
the resource and value of alternative policies af ecting the resource can then
be evaluated using consumer surplus calculated from the demand curves.
The advantage of TCM is that the data collected involves actual consumer
behaviour. Its chief disadvantage is that it does not accurately value trips
for multiple purposes. TCM has been used extensively in the United
Kingdom and United States for valuing the non-market benei ts associ-
ated with national parks and managed landscapes including public forests
(Bowes and Krutilla, 1989; Benson and Willis, 1991; Whiteman, 1991).
A second method of estimating wildlife value is a stated preference
method, the contingent valuation method (CVM). This involves the
construction of a hypothetical or simulated market for an environmen-
tal or wildlife resource. Contingent valuation techniques use surveys to
elicit individuals' preferences for public goods by i nding out what they
would be willing to pay (WTP) for them, or what they would be willing to
accept as compensation (so that they would not be worse of ) for specii ed
changes in them. This approach circumvents the absence of markets for
public goods by presenting consumers with hypothetical markets in which
they have the opportunity to purchase the good. Willingness to pay is
determined either through a written questionnaire or using bidding games
implemented by personal interviews. Demand curves are then constructed,
and consumer surplus used as a measure of use and non-use value. The
