Environmental Engineering Reference
In-Depth Information
found in the densely populated areas in central and
western Europe, including the present attempts to
restore natural floodplains along all large rivers of
western Europe.
2
The
arcadian
concept ('semi-natural landscapes',
see Westhoff 1952; 'semi-natural ecosystems', see
Christensen
et al
. 1996; 'arcadian view', see
Worster 1977; 'pastoral attitude', see Schama 1995)
is based on the long tradition of human inter-
ference with nature and is especially dominant in
Europe. From the 18th century onwards the idea of
'nature' to European citizens was highly influenced
by philosophers from the Age of Reason who
depicted the simple, happy life in the countryside
close to God. A second impulse came during the
20th century when ecologists realized that the
highest (plant) species richness in history was
found in these semi-natural landscapes. Present-day
European nature conservation organizations often
pursue this goal by mimicking ancient agricultural
management techniques (Bakker 1989). Humans
play a very active role: arcadian nature would not
exist without massive human impact in the form
of mowing, cutting back of hedges, slight drainage
of species-rich meadows, etc.
3
The
functional
concept ('rural landscapes', see
Westhoff 1952; 'intensively managed systems',
see Christensen
et al
. 1996; 'imperialistic view', see
Worster 1977) is heavily anthropocentric and con-
siders nature as something to be used by humans.
In fact this is the dominant view of nature. In the
past, agriculture, forestry and fishery were the
main domains of resource use, whereas modern use
also includes other ecosystem functions such as clean
air and flooding prevention, which can be asso-
ciated with the notion of ecological engineering.
with different nature concepts (Fig. 1.3). Using these
different scenarios as targets raises the additional
problem of timescale - those scenarios nearer to the
present state of the landscape will be achieved more
readily and in less time than those that require extens-
ive development of woodland, for example.
We must therefore ask, what are the components
of the system that we are restoring, and for what pur-
pose are we restoring them?
1.2.2 Biodiversity
One activity where restoration ecology has a clear man-
date for action from society is in the field of conserving
and enhancing biodiversity. The Rio Protocols (UN
1992a) and the European Union (EU) demand action
under Biodiversity Action Plan orders. Here the
requirement to audit and act on biodiversity targets
with respect to particular species is now a well-
established process. Further to this there has been
legislation passed and likely to be adopted by the EU
with respect to environmental liability. There will be
a legal requirement for damaged ecosystems to be
restored, or mitigated by restoration elsewhere, at the
expense of the party responsible for the damage.
Despite the widespread acceptance of biodiversity as
a base for conservation and restoration, there is a lot
of confusion associated with this term. In its original
form it meant 'the whole variety of life on Earth'
(Gaston 1996a) but this concept is not immediately
useful for basing concrete actions upon. Therefore, the
term is mostly used in association with a certain area.
Biodiversity can be considered at three levels:
1 genetic diversity
is the amount of variation within
or between species;
2 species diversity
means mostly just species richness;
3 ecosystem diversity
is the variety of ecosystems on
the planet (or part of it).
The above-mentioned example of floodplain regen-
eration is a typical case that was born from two
completely different views of nature. Adepts of the
functional approach emphasize the reduction of
flooding risks, whereas adepts of the wilderness
approach like this idea because a self-sustaining
ecosystem is restored. The concept of nature determines
the restoration goal in a given situation and this
determines the necessary actions and spatial layout.
Harms
et al
. (1993) compared the spatial conse-
quences of alternative restoration targets, associated
Most often the second meaning is used (species rich-
ness), but an implicit assumption in this use is that
all species (of a given area) are known. This is
evidently not true: at present there are about 1.75 mil-
lion species described whereas the estimates of the total
number of species vary between 7 and 20 million
(Groombridge & Jenkins 2000). Independently of
