Environmental Engineering Reference
In-Depth Information
about the aims of nature conservation became under
debate, mainly related to the degree of desired or
allowed human
intervention
. In 1945, for example,
the Royal Dutch Society for Natural History (KNNV)
organized a conference to identify and agree on the
choices for aims of nature conservation and manage-
ment (van der Windt 1995). The dilemmas were
discussed among landscape architects, nature conser-
vationists and managers, and scientists. A choice was
made for
seminatural ecosystems and landscapes
as a primary goal of nature conservation and manage-
ment. The most important conclusion was that the
principle of including human interventions in nature
was no longer questioned, thus leaving room for differ-
ent options. Currently, it is common use to recognize
three archetypes of 'nature', dependent on the degree
of naturalness (see Swart
et al
. 2001 ): (1)
wilderness
,
or self-regulating near-natural ecosystems, (2)
Arca-
dian or seminatural ecosystems
, based on a long
history of extensive human interference, and (3) inten-
sively managed
production systems
. The intensity of
human impact may be strong or moderate or even zero,
depending on the view of nature applied to different
sites, ranging from production systems to some kind of
wilderness. In Figure 1.3 we used these three catego-
ries, and added the notion of
over - exploitation
as a
fourth step in the disturbance of a system to an alter-
native state; the latter state can no longer be considered
part of 'nature'. In the next section we will present
views on various options for the repair of different dis-
turbed states.
at almost non-assisted natural recovery, (2)
ecological
restoration
, that is, the return to some historic
refer-
ence system
, representing pre - disturbance condi-
tions, be it natural or seminatural, (3)
ecological
rehabilitation
, that is, the improvement of
ecosys-
tem functions
without necessarily a return to pre-
disturbance conditions, and (4)
reclamation
, that is,
conversion of heavily degraded land such as post-
mining areas to a productive condition.
However, new problems continually pop up. Nature
management, as agreed upon, and the restoration of
abandoned production systems, may result in successes
and failures. Sometimes the return to past ecosystem
types simply can not be achieved by re-applying the
former management measures. Irreversible environ-
mental conditions, for example due to severe drainage
of peat soil or high soil-nutrient loads, could prevent or
severely retard a return to the past, and this raises the
need to consider other options. Currently in the fi eld of
restoration ecology, it is generally accepted that a return
to past ecosystems, indeed a return to the past in general
is, strictly speaking, not possible; history can not be
repeated. This implies that the notion of
reference
systems
should no longer be conceived of in a narrow
fashion, or restricted to an idealized situation of the
past. Instead, it can be conceived, and then utilized, in
many different ways. A reference system may change
over time and may in fact be developed as a series of suc-
cessive reference states or systems (Figure 1.4).
There is also a need to recognize uncertainties involved
in restoration, and the reality that many ecosystems
today are in fact
emerging ecosystems
(see Part 4),
since the world has changed so radically, from a biolo-
gist's point of view, and will continue to change, as a
result of climate change, land use change, biological
invasions and so on. In Chapter 3, we will also encounter
the notion of
novel ecosystems
that have entirely
altered from historical ranges. There the main aim of
restoration might be to ensure the maintenance or opti-
mization of the fl ow of material ecosystem goods and
services with less concern for cultural services or biodi-
versity or any spiritual or cultural ties with the past.
Several chapters in Part 3 will deal with this theme, and
we will refl ect on the different options available in the
three concluding chapters of Part 4. Now, at the begin-
ning of our journey through this topic, we would like to
emphasize that ecologists' primary job is to provide as
much information as possible to make predictions, and
effective applications in ecological restoration projects,
based on historical, analytical, and experimental
1.4
VIEWS ON RESTORATION
The focus of nature conservation has been on the pres-
ervation of near-natural and seminatural ecosystems
through preventing them from being degraded. Eco-
logical restoration has much broader perspectives,
aiming at the repair of damage, now including the eco-
logical restoration or rehabilitation of production and
exploitation systems (see Figure 1.3). And again, there
are often diffi cult choices to be made, even when the
general goal of ecological restoration has been agreed
upon. Indeed, in most situations a broad range of
targets can be distinguished, from spontaneous or
assisted recovery to the former state, to a state that one
could call a halfway condition with respect to the
former state. Currently, different options for restoration
are recognized: (1)
near - natural restoration
, aiming
