Concepts in restoration ecology - Restoration Ecology - page 27

variability, ecotypes) be recognized here? To tackle such
problems, we need answers to three questions.

fitness of transplanted populations does not imply any
risk, apart from the risk of failure of the transplant-
ing activity in cases of strong ecotypic differentiation.
It seems better, he argued, to restore a population with
its fitness reduced by a few per cent, than to restore
no population at all. Keller et al . (2000), however,
warned that these suggestions should not be applied
uncritically within declining populations. In cases of
re-introductions of animal species, similar discus-
sions and viewpoints can be found in the literature.
Abrams (1996) argued that current theory is insuffi-
ciently developed to provide guidance in predicting
what might happen to either trait values or popula-
tion densities of other species after the addition or
deletion of a species. And, indeed, both positive and
negative effects have been found (see Chapter 7).
In summary, failures of re-introduction may be
considered a significant risk, rather than unintended
aspects of success, provided that the habitat is of
adequate quality. Species characteristics such as
competitive aggressiveness in an ecological sense are
related to the introduction or invasion of aliens,
rather than to re-introduction of species sensu stricto .

1 Can we successfully distinguish invading aliens from
non-successful invaders and from native species?
2 Can the abiotic environmental conditions have
changed to such an extent that the statement that
the species to be re-introduced belongs to the com-
munity cannot stand any longer (in other words, is
the reference community obsolete)?
3 Can populations of the species to be re-introduced
ecologically and genetically have changed in such
a way that the intended re-introduction can turn
out to be an unintended invasion?

Is there a risk of re-introduced species behaving like
alien invaders? Sakai et al . (2001) reviewed aspects
of the population biology of invasive species, such as
their life-history characteristics, their genetics and
evolutionary potential, the susceptibility of com-
munities to invasion and the invaders' impact on the
invaded communities. Though a lot is known about
invasive species and their impact, it remains difficult
to predict the behaviour of populations of invaders
(see also Mack et al . 2000). There is, we think we are
justified in concluding, no a priori risk of re-introduced
species behaving as alien invaders, but how then
can criteria for re-introduction be identified so as to
exclude the risk? Here we refer to Strykstra (2000),
who proposed to address the following topics in any
plan for re-introduction: (i) the significance of the re-
introduction, both for the target area and for the species
involved, (ii) the match between the area and the species
involved in (bio)historical terms, (iii) the suitability of
the environment in the area for the species involved
and (iv) the material and the method used. These issues
will be elaborated in Chapters 5 and 7. Here, we will
pay particular attention to the latter aspect, the ques-
tion to what extent intraspecific variation should be
taken into account in re-introduction projects.
Does intraspecific differentiation matter? van
Andel (1998b) reviewed the results from reciprocal
transplant studies that had been performed to illus-
trate population differentiation and local adaptation,
rather than to test potential risks of transplantations.
In essence, these data are apt to be applied to the new
problem. The author concluded that, although local
adaptation does occur, a small reduction in the

2.5 Concluding remarks

In this chapter, we have provided a brief overview
of the field of restoration ecology. We started by
discussing the concepts of stability and disturbance
representing a systems approach, applicable to eco-
systems, and communities or populations, because
steady states and disturbances may occur at any
organizational level. The biodiversity concept is
confined to tangible organisms and has only during
the last decade been linked to a systems approach (e.g.
Tilman 1996, Loreau et al . 2002; see also Chapter 4).
Biodiversity is fundamentally a societal concept (see
Chapter 1), adopted within restoration ecology with
the challenge to get the issue operationalized (this
chapter). Evolutionary theories, though in the core of
thinking about the origin of biodiversity, have so far
not been included in the field of restoration ecology.
These fields of interest are, apparently, too far away
to be made applicable, but it is our hope that this may
change quite soon.
In the five theoretical chapters that follow
(interactions at the level of landscape, ecosystem,