Geoscience Reference
In-Depth Information
positive and negative impacts on the full range of
ecosystem services resulting from interventions in
aquatic ecosystems.
and complexities of operational decision-making
and also the need to find simple means to retain
a systems-level overview of likely outcomes. From
this overview, limited resources can then be
directed at the most significant likely impacts or
knowledge gaps.
Methods: ecosystem services
case studies
An inclusive approach to
quantification and valuation
As ecosystem services describe the multiple benefits
that society derives from ecosystems, they are
inherently suited to valuation. Economic appraisal
or other forms of quantification are not integral
to ecosystem service assessment, but they provide
a common basis for assessing the relative impacts
across different types of ecosystem services.
Nevertheless, for credibility it is important that
the methods used for economic assessment avoid
double-counting, but account for both positive and
negative impacts.
The dangers of double-counting ecosystem
services are profound. Turner
et al
. (2008)
distinguish 'intermediate services', which occur
within ecosystems but which are not directly
consumed by people, from 'final services' which
people use and for which markets (trading in
services with associated price information) are
more readily identifiable. An example is the
contribution of the 'intermediate' regulatory
service of 'water purification and waste treatment'
to the 'final' provisioning service of 'fresh water'
(
sensu
Millennium Ecosystem Assessment,
2005). This approach can be taken further
by recommending valuation only of those
components comprising 'goods', defined as
the products of ecosystem services used by people
and for which market values can be more readily
derived (Bateman
et al
., 2011). However, the
danger of this approach is that unvalued services
may remain overlooked in policy and decision-
making,
Taking an ecosystem approach
Not all studies claiming to take an ecosystem
approach actually do so; this perpetuates the
traditional narrow approach of pre-selecting
services considered to be 'important', with the
implicit assumption that all other services must
be less important or unimportant. For example,
the
Land Use and Environmental Services
report
(Land Use Consultants with GHK Consulting,
2009) pre-selected four 'important services'
(regulation of water quality, availability of water
resources, management of flood risk, storage of
carbon in soils), explaining this pre-selection as
a practical means of coping with the complexity
and costs entailed in addressing all services. These
studies merely reaffirm previous 'exploitation
economics' decisions (
sensu
Johnson
et al.
, 2007),
that emphasize the values of selected beneficial
outcomes, generally for a few, local and influential
stakeholders, while overlooking services beneficial
to
ecosystem
integrity
and
wider
society
as
a
whole.
By contrast,
An Introductory Guide to Valuing
Ecosystem Services
(Defra, 2007a) recommends a
weighting system based on expert assessment of
the likely direction and significance of impacts
across all ecosystem services (Table 25.1). This
weighting system recognizes the resource pressures
Table 25.1
'Likelihood of impact' weighting system
(from Defra, 2007a).
Score
Assessment of effect
unwittingly
perpetuating
the
narrow
++
Potential significant positive effect
'exploitation
economics'
which
historically
has
+
Potential positive effect
caused ecosystem depletion.
0
Negligible effect
-
Potential negative effect
Case study selection
Very few economic studies have applied an
approach that values or weights ecosystem services
-
Potential significant negative effect
?
Gaps in evidence / contention
