Environmental Engineering Reference
In-Depth Information
that occur in the reference ecosystem, (2) the primary
presence of indigenous species, (3) the representation
of all known functional groups necessary for the con-
tinued development and/or stability of the system, (4)
the appropriate physical environment to sustain repro-
ducing species populations, (5) the normal function-
ing, and the absence of signs of dysfunctioning of the
system, (6) the suitable integration into a larger eco-
logical matrix or landscape, (7) the elimination or
reduction of threats to the health from the surround-
ing landscape, (8) a suffi cient resilience to endure the
normal periodic stress events and (9) an ability to be
self-sustaining to the same degree as its reference eco-
system. Clewell and Aronson (2007), exploring these
' desirable attributes ' , consider the formulation of
' standards ' a useful ' broad - brush ' approach, in each
case to be judged in comparison to a reference system.
Though they recognize that it may be impossible to
meet all these criteria, they consider such standards
indispensable for the evaluation of monitoring results
during the trajectory towards any goal.
We recall that
ecosystem structure and func-
tioning
are core issues in any ecological restoration
project, also in cases of a focus on the reintegration of
a landscape or the rescue or reintroduction of a species
population. At the same time, we recognize through-
out this topic that understanding of ecosystem proc-
esses requires knowledge of landscape ecology,
community ecology and population ecology and genet-
ics. Therefore, each of these subdisciplines of ecology
is discussed in Part 2 of this topic. Here, we introduce
a number of key topics in restoration ecology related to
landscapes, ecosystems and biodiversity.
2011 ). Indeed, ' natural ' or ' seminatural ' ecosystems
are part of a landscape matrix with several interacting
systems, including production systems or over-
exploited systems, as per Figure 1.3.
In Chapter 5, on landscape ecology, the authors
propose a new defi nition of 'landscape', as the initially
clear defi nition, as given by physical geographers, has
steadily become blurred after ecologists adopted the
term 'landscape ecology' for their studies on the spatial
dynamics of individual plant and animals species.
Here, we would like to clarify the different positions in
the scientifi c literature. From a human perspective, a
landscape
is commonly defi ned as a geographical
area that can be mapped and interpreted from aerial
photographs, forming a mosaic of interacting systems
that may include ' natural ' ecosystems, agro - ecosys-
tems, villages, and industrial areas (cf. Turner
et al
.
2001). This notion of landscape has ecological, histori-
cal, economic and other human dimensions; spatial
patterns and transport of matter and organisms are
also important aspects. Ecologists studying
metapop-
ulations
, at a landscape or regional scale, have
adopted the term 'landscape ecology'. In this approach,
a landscape is defi ned from the perspective of varying
kinds of organisms (Wiens 1976), all of which move
within and among habitat patches characterized by
some degree of connectivity. As an analogy, the term
'landscape genetics' was recently coined to describe a
study that aims at mapping how genes fl ow at the land-
scape scale (Manel
et al
. 2003 ). These landscape - scale
ecological and genetic studies might, after all, have
been better named 'spatial ecology and genetics', to
avoid confusion with the geographical approach to
' landscape ecology ' .
There is still more to be clarifi ed. The
habitat
of a
species may become fragmented in a landscape, result-
ing in habitat patches with local populations. The logic
term
habitat fragmentation
(used in Chapter 7) has
then also confusingly been termed 'landscape fragmen-
tation ' , in Chapter 5 defi ned by the extent of habitat
destruction. Once the reader understands how to inter-
pret the existing literature, including the terminology
used, we will have completed this guided tour of fun-
damental - and hopefully unifying - concepts.
2.3
LANDSCAPES
As mentioned, the focus of ecological restoration in
this topic is on entire ecosystems, as per the
SER Prim-
er ' s
defi nition (SER 2004). In Part 3 of this topic, the
reader will fi nd no less than 11 applications of this
philosophy. However, as we will see in several of these
chapters (especially 16-19, dealing with wetlands),
and still more explicitly in each of the next three chap-
ters (3-5), a 'landscape perspective' on the restoration
of ecosystems is essential. Ecosystems can be defi ned
individually, but they do not function independently of
their biotic and abiotic surroundings. Their spatial and
ecological relationships at the landscape scale matter a
great deal to what happens within them (Thompson
2.4
ECOSYSTEMS
In view of the central task of ecological restoration to
restore degraded ecosystems, we must refl ect further
