Environmental Engineering Reference
In-Depth Information
consequences for other aspects of the system which were not explicitly
recognised or managed for, but when changed become a significant issue
(e.g., flood regulation).
3. The criterion that the functions and services in a system are assessed in
terms of their sustainability, not exploitative potential. Clearly, there are
some aspects of ecosystems where potential short-term delivery rates of
goods and services may be high, but have no prospect of being maintained
in the long term. Any assessment of service provision and hence any
measure of quality depending on it must work as far as possible with
sustainable levels of service provision.
4. The ability to incorporate existing elements of ecological quality where
these are relevant, as a component, but not the whole, of the assessment.
These existing criteria may be quite different; for example, one important
group of criteria used in measuring ecological quality in freshwaters are
thresholds of chemical concentration, or biological toxicity, which may be
quite precise quantitative measures, encapsulated in legislation such as
that for drinking water supply. At the other end of the spectrum, criteria
such as those discussed earlier, of 'naturalness' or closeness to some pre-
human state, may still be criteria that we wish to take account of, but need
to be incorporated in a broader assessment, not the sole target.
Several elements emerge here: the inclusion of multiple services, the facility to
include existing criteria and the notion of demand for services as being an
element of the context in which quality is evaluated. Taking these, we propose
that one way of assessing quality, which could capture all the features above, is
to use the match between the demand for a range of services, and the extent to
which that demand is met sustainably, as our index of quality: a system that
can support, in the long term, the range and magnitudes of services we desire
from it is, in some sense, of good quality. We term this approach of matching
requirement and provision across a number of ecosystem services the Ecosys-
tem Service Profile (ESP), and we feel that such a measure has some potentially
useful characteristics.
The first is that, although services are delivered and measured in many
different ways, the matching of requirement and provision for each service is
likely to be in the same units, and it may avoid the problematic job of
translating services into common units (monetary other otherwise).
Second, if for a range of services, the match between demand and provision
can be assessed, then strong mismatches in which demand exceeds provision
draw attention to the places where management might be directed to
improve quality. Clearly, improving such a mismatch might involve the
increase in provision, or decrease in demand, both valid management
options. This makes the important point that quality improvement might
come from reducing demand for something. Whilst this might initially seem
