Environmental Engineering Reference
In-Depth Information
productivity curve, i.e. the 'hump-backed distribution'
curve, we note that different productivities are linked
with characteristic species densities (Al-Mufti
et al.
1977; see also Fig. 5.1 in this volume). Therefore, max-
imum species density
does not
equate to preservation
of the most species, as those habitats requiring con-
ditions found at either end of the curve (woodlands,
tall herbs) will be excluded. Although often con-
sidered otherwise, biodiversity (in whatever sense)
cannot be used as an objective yardstick and has every-
thing to do with valuation and thus with the societal
goals of the actors involved.
direct-use values can be expressed rather easily in
monetary terms this is virtually impossible for non-use
values. In the latter type of case economists often rely
on so-called willingness-to-pay enquiries, e.g. house
pricing in attractive areas. This approach can also
be used in a negative way (avoidance costs), for ex-
ample in an enquiry into how much money people are
willing to spend on travel to avoid living close to the
factory where they work. Useful as this willingness-
to-pay approach may be, it also has certain disad-
vantages; for example, it is highly context-sensitive
(people tend to regard natural values much more highly
in a polluted environment that in a natural setting),
and dependent on socio-economic circumstances. De
Groot
et al
. (2002) followed a different approach (see
below p. 9) and distinguished four types of
function
that ecosystems provide. Once this approach is made
operational it would provide a basis for integrated
cost-benefit analysis and balanced decision making not
only for sustainable use and conservation of natural
capital as the authors suggest, but also for resource-
effective ecological restoration. It could also aid in the
development of a 'restorability index' for sites in
varying degrees of degradation.
One estimate (Boumans
et al
. 2002) suggests that
the value of global ecosystem services is about 4.5 times
the value of the Gross World Product. This approach
appears attractive, as it talks to policymakers at an
international level in units that they can readily
understand. The danger lies in the fact that, accurate
estimations of equivalency aside, it can lead to the
assumption that given enough money anything can
be replaced. This is not the case for species that are
nearing extinction.
However, if a rational and sustainable case for this
type of approach can be developed, it lends itself very
readily to assessing the worth of ecological restora-
tion as a societal endeavour.
1.2.3 Ecosystem valuation
Economic valuation
One area in which the societal justification for eco-
logical restoration may be tested is that of ecosystem
valuation. The concept of ecosystem valuation is one
undergoing much examination and development
following seminal works by Helliwell (1969), and was
given added impetus as a result of work by Pearce
(1993), produced in response to the need for pro-
viding policy makers with a means of understanding
carbon-emission control. A significant attempt was
made for a global assessment of ecosystem services
reported by Costanza
et al
. (1997). For a substantial
review of the concepts and procedures involved we
refer the reader to Daly and Farley (2004).
The basic premise upon which economic valuation
systems rest is that the functions, goods and services
that an ecosystem provides can be valued in monet-
ary terms so that a cost-benefit analysis can be carried
out. Dabbert
et al
. (1998) distinguished four types of
value
that ecosystems provide to society:
1
direct-use values, e.g. groundwater for drinking
water and fish stocks;
2
indirect-use values, e.g. filtration and/or chemical
alteration of pollution, and fixation of CO
2
;
3
optional values: the values of using and experiencing
areas, e.g. for recreational purposes;
4
non-use values: the intrinsic values of the mere exist-
ence of ecosystem, e.g. for species survival.
Ecological valuation
Several novel approaches for considering ecosystem
properties in a societal context have appeared re-
cently, and we outline some of these below.
The
ecological footprint
concept has been devel-
oped in the last decade. The area of land required to
support the consumption of anything may be cal-
culated, from the level of an individual to the scale
From top to bottom it is increasingly difficult to use
classical economical valuation techniques. Whereas
