Environmental Engineering Reference
In-Depth Information
cultures to higher convergence in all fi ve MCRs, just as
elsewhere, but still the 'fi ngerprint' of land use history
is strong enough to infl uence current restoration
approaches, of which there are a large number indeed
in the various MCRs. As elsewhere, the fi rst step
towards restoration is to identify and halt degradation
processes. Such processes affecting MCRs today are
land degradation produced by long-term overuse of
natural resources, and further degradation produced
in case of land abandonment in semi-arid areas,
anthropogenic forest fi res and the spread of invasive
species. Once one or more ecological
thresholds
have
been crossed, however, certain degradation processes
may not be reversed spontaneously, but only through
human
intervention
in the form of restoration
actions and manipulations. In particular, in recent
decades, anthropogenic fi res have increased in fre-
quency and intensity, not only in Chile (see above) but
also in the other MCRs. This represents a serious threat
to ecosystems, wild biota and, of course, the built envi-
ronment. To cope with fi re-induced damages to ecosys-
tems and to humans,
post - fi re rehabilitation
started in
California in the 1930s and is now being applied in the
other MCRs as well. Later in this chapter (section
11.2.5), we will dwell on the topic of fi re regime inter-
vention and restoration in some detail.
Since the mid-nineteenth century, several countries
in the Mediterranean Basin have carried out
affores-
tation
programmes to protect watershed headwaters
areas, regulate streamfl ow, reduce fl ash fl oods, control
soil erosion and provide forest products. Programmes
in Spain (Mart í nez Garc í a
et al
. 1996) and France (Val-
lauri
et al
. 2002) were particularly extensive. In con-
trast, afforestation in central Chile only began in the
mid-twentieth century, and there top priority was
given to timber production, and most often the use of
exotic trees was favoured over native forest restoration
(Becerra & Bustamante 2009 ). In south - western Aus-
tralia and South Africa, afforestation and restoration
practices have also begun in the recent past, but gener-
ally speaking the strongest emphasis of restorationists
in those two MCRs has been put on the control of inva-
sive alien species (e.g. Richardson & van Wilgen 2004),
as is now the case in California as well (E.B. Allen
et al
.
2005 ; D ' Antonio & Chambers 2006 ).
The rapid increase of global trade and travel in
recent decades has facilitated the spread of invasive
organisms of all kinds. In the case of the MCRs, the
predominant direction of invasion has been from the
Mediterranean Basin to the other four regions, and
there have also been major invasions of alien plants
from Australia into South Africa (see also Chapter 20).
Negative effects of
invasive species
on Mediterranean
ecosystems include reduced biodiversity changes in soil
properties that make the site unsuitable for native
species (Yelenik
et al
. 2004), and more frequent fi re
following annual grass invasions (Minnich 2008).
However, biological invasions of both plants and
animals are now clearly on the rise in the Mediterra-
nean region as well, and much more attention is being
accorded with this problem, by ecologists, horticultur-
ists and conservation authorities (Quézel
et al
. 1990 ;
Filippi & Aronson 2011a,b ).
11.2 RESTORATION OF
MEDITERRANEAN-TYPE WOODLANDS
AND SHRUBLANDS
In this section, after discussing restoration priorities
(section 11.2.1), we review some of the most promi-
nent tools used in ecological restoration programmes
in the range of ecosystems covered in this chapter.
These include (1) post-fi re emergency rehabilitation
techniques such as sowing of herbaceous cover crops
and mulching (section 11.2.2), and techniques to
ameliorate reintroduction of key native tree species
such as microsite preparation, tree shelters and bird
perches (section 11.2.3), (2) invasive plant species
control (section 11.2.4) and (3) the restoration of
natural or moderate, cultural fi re regimes (section
11.2.5). Approaches and techniques vary from region
to region. We shall only explicitly consider
rehabilita-
tion
activities as part of early post-fi re measures,
although they have short-term objectives not always
related to the
recovery
of reference or pre-disturbance
ecosystems. Furthermore, we will concentrate on the
Mediterranean Basin, Chile and California. For more
information on current restoration activities in Aus-
tralian and South African MCR woodlands and shrub-
lands, see Chapters 4 and 20, respectively.
11.2.1
Restoration priorities
The specifi c objectives of restoration differ widely
among the different Mediterranean-type
woodland
and
shrubland
ecosystems, and are determined by the
degree of degradation, and by climatic, biotic and
socio-economic constraints (Table 11.1). As elsewhere
