Environmental Engineering Reference
In-Depth Information
of the whole planet (Wackernagel & Rees 1996,
Wackernagel
et al
. 2002). Once the area of land
required is larger than that directly available, then the
consumption is viewed as unsustainable. This provides
a useful shorthand for the ecosystem valuation
approach outlined above and is comprehensible to the
non-expert. This approach has been criticized as
being an over-simplification and being too dependent
on scale (van den Bergh & Verbruggen 1999). These
technical criticisms are resolvable, however, and we
suggest that ecological restoration may be viewed as
a tool for reducing our ecological footprint. By
restoring ecological capacity to the degraded system
in one region of a nation, we could reduce the foot-
print of that nation as a whole. This leads to the ques-
tion, what contributes to the size of the footprint on
the positive side? This is explored in the following para-
graphs. This issue will be referred to once again in
the last part of this volume.
A concept which has emerged in the last decade is
that of
ecosystem health
. Ecosystem health can be
defined as comprising a set of indicative factors
(Rapport
et al
. 1998):
2
habitat functions: providing suitable living space for
wild plant and animal species;
3
production functions: providing natural resources
from which to make goods (consumable and
structural);
4
information functions: providing opportunities for
cognitive development.
This analysis has a considerable advantage over other
approaches in that the economics of restoration are
well characterized, and therefore have increased the
chances of funding for, for example, restoration of
floodplains by taking down levees or berms to re-instate
flood storage.
1.3 A call for scientific analysis
1.3.1 Level of ambition
Restoration scientists usually stress the necessity to
define and agree upon common targets in restoration
projects (Hobbs & Norton 1996, Pfadenhauer &
Grootjans 1999, Bakker
et al
. 2000). We agree with
their plea for clear and measurable targets but would
like to take the argument somewhat further. A
definition of targets depends to a large degree on the
level of ambition for which regeneration plans are being
developed. Hobbs and Norton (1996) suggested a
number of reasons why restoration might be carried
out: (i) to enhance conservation values in protected
landscapes, (ii) to enhance conservation values in pro-
ductive landscapes, (iii) to improve productive capab-
ility in degraded productive lands and (iv) to restore
highly degraded but localized sites such as mine sites.
These reasons may be consistent with the schema
devised by van Diggelen
et al
. (2001), who distinguished
three levels of ambition of programmes aimed at
reversing degradation of ecosystems. The first and most
ambitious level could be called true
restoration
and
consists of a reconstruction of a previous situation
or self-sustaining target. This includes not only the
re-establishment of former functions but also of the
characteristic species and communities. The principal
problem with taking this absolutist stance is that, if
based on past environments and not current or future
circumstances, it is likely to be unsustainable. If we
accept, however, that we are intending to re-instate
• vigour: activity, metabolism or primary productivity;
• organization: diversity and the number of inter-
actions between system components;
• resilience (or counteractive capacity): a system's
capacity to maintain structure and function in the
face of stress.
The concept of ecosystem health is the focus of quite
heated debate. Some commentators suggest that it is
a ridiculous notion (Lancaster 2000), and others offer
a critical analysis (Calow 1995). Harris and Hobbs
(2001), however, suggest that ecological restoration
could be regarded as one of the clinical tools for restor-
ing ecosystem health, and provide numerous examples
to that effect. In this sense ecosystem health provides
the tools for assessment and ecological restoration the
treatment (see also Chapter 2 in this volume).
De Groot
et al
. (2002) suggest that there are four
principal functions supplied by ecosystems, without
which human society could not function:
1
regulation functions: providing maintenance of
essential ecological processes and life-support
systems;
