Environmental Engineering Reference
In-Depth Information
Route of transmission:
Natural dispersal
Deliberate re-introduction
Accidental re-introduction
Propagule source:
Habitat
Seedbank
Receptor system
Fig. 1.6
Source, pathway and receptor system
for re-introduction of biotic components to
degraded ecosystems.
1.3.5 How to measure the degree of
restoration success?
unless human society approves the goals and objectives
of restoration. In addition, restoration will not persist
unless human society has sufficient esteem for the
restored ecosystem to protect its integrity.'
So we have to address all types of target, some
directly by direct physical manipulations, others by
incorporation of stakeholders and the full socio-
economic dimension, in order to achieve truly sus-
tainable restorations, and be cognisant of the need to
reconnect processes and functions with the biological
components of a system, after abiotic thresholds have
been overcome (Hobbs & Harris 2001). This is a hard
task, as resources often only allow, or are granted for,
one of these goals. This is because of the multi-
plicity of funding streams aimed at each of these
types of target, a confusing melange of government
agencies, non-governmental organizations, charities
aimed at single species (hedgehogs appear to be a par-
ticular favourite), and individual activists and vol-
unteers. Funding may in fact be completely absent
for particular groups, and legislation may make cer-
tain restoration goals actually illegal, as with the
re-introduction of some native species into agricul-
tural areas being prohibited as they are regarded as
noxious weeds. In certain parts of Europe there is
a cultural and legislative resistance to the active
replanting and re-introduction of species, rather rely-
ing on the dictum 'build the field and they shall come'.
This completely ignores the importance of migration
rates of sources of biological diversity: how far away
the sources of biological potential are, and what the
routes of transmission are. We might suggest an
inverse of the risk-assessment approach (Fig. 1.6).
Here the risk of failure of transmission is the object
of interest - we must know this in considerations of
re-establishment of complete species inventories. The
route of transmission is often limited for technical
reasons, but in some societies the greater obstacles are
cultural.
In the SER Primer on ecological restoration (SER 2002)
a set of aspects of the structure and functioning of
ecosystems was pointed out that can be used to
assess the effectiveness of the success of any given
restoration project. In our opinion not all aspects are
applicable at all ambition levels. In Table 1.2 we indic-
ate what attributes we consider applicable for the sev-
eral ambition levels. Ideally the effect of ecological
restoration is as depicted in Fig. 1.7. The restored object
changes under the restoration management towards the
target in the same way as it would without human
interferences, only much faster. In practice, however,
failure occurs very often. It is, therefore, necessary
to measure and monitor the degree to which the
restoration has been successful and appropriate;
timely monitoring programmes are an indispensable
part of the restoration process.
Dale and Beyeler (2001) mentioned several criteria
that ecological indicators should fulfil in order to be
suitable as measurements of ecosystem quality. They
should be easily measured, be sensitive to anthropo-
genic pressures, be anticipatory - giving early signals
of a treatable larger problem, allow for adaptive
management intervention, be integrative, have known
responses to stress, disturbances and time, and have
low variability in response. Without these, it is
difficult to see how a sustainable measurement and
monitoring programme would be sustained by soci-
ety, so we must ensure that the full range of spatial
and temporal variability is captured by the critical com-
ponent states measured.
Clearly, using Hobbs and Norton's (1996) schema
(section 1.3.2) we can choose indicators from all six
of their attributes and apply them to the type of time-
series analysis suggested in Fig. 1.7. This will only be
of use, however, if we are able to distinguish change
