Environmental Engineering Reference
In-Depth Information
sage scrub, then periodic mechanical or chemical
control may be required (E.B. Allen
et al
. 2005 ), and
invaded systems will require long-term management
to achieve and then maintain desired conservation
values.
houses interspersed with vegetation, generating a
large wildland-urban interface. In such conditions,
natural fi re regimes are diffi cult to restore without
affecting human activities and infrastructures. There
is still a lack of cultural, political and socio-economic
understanding of living in fl ammable ecosystems
(Pausas & Vallejo 2008 ).
• As mentioned above, invasive alien species are one of
the major problems in MCRs and, with the exception
of the Mediterranean Basin (where post-fi re aliens are
relatively uncommon), and frequent fi res often increase
the opportunities for invasion by alien plants (Keeley
et al
. 2005). Given the current high (unprecedented)
propagule pressure of alien species, restoring natural
fi re regimes may imply the increase of invasive alien
plants (Keeley 2006). This often leads to a challenge for
managers who must choose between restoring natural
fi re regimes and altering those fi re regimes to favour
communities of native species, while altering the
natural community structure.
In addition to these diffi culties to restore the historic
fi re regime, climate is changing very fast in many or all
of the MCRs, and due to the strong link between
climate and fi re, restoration of fi re regimes should also
be conducted with full consideration of projected cli-
matic scenarios of coming decades. Moreover, climatic
change also has consequences on other factors that
may modify forest structure and fl ammability, such as
drought and pests. According to some researchers (e.g.
Fulé 2008), such considerations make local historical
references of limited value while references from drier
sites become more appropriate. Needless to say this is a
fertile topic for debate, and long-term research and
adaptive management will be necessary on a site-
specifi c basis.
11.2.5
Restoration of fi re regimes
One of the challenges in landscape management of
Mediterranean ecosystems is to restore, or reinstate,
natural (historic) fi re regimes. For this purpose, both
fi re suppression and prescribed fi res may be appropri-
ate tools to test. However, prescribed fi res have also
been used to reduce fuel loads and fi re intensity without
examining the natural fi re regime. Indeed, restoring
fi re regimes is never a simple task because of the impact
on and implications for native biodiversity. The main
diffi culties are as follows:
• Natural fi re regimes vary spatially with climate and
vegetation structure, and different ecosystems have
species adapted to different fi re regimes. Moreover, the
natural or historic fi re regimes are not always known.
In ecosystems with surface fi re regimes, fi re scars from
old trees can be used to infer past fi re regimes; however,
in crown - fi re ecosystems (e.g. the chaparral- or
matorral-like communities of all MCRs), this is not an
option as most trees are fully burned and the main
stem dies after the fi re. In ecosystems intensively and
perhaps over-used for millennia, including many in the
Mediterranean Basin, old trees are very rare and can
hardly be used for fi re regime estimation; in such situ-
ations we lack an historical reference. Aerial photogra-
phy and remote sensing have been used to reconstruct
fi re regimes to the earliest available imagery.
• Most fi res in natural fi re regimes occur in summer,
when vegetation is most fl ammable, while for safety
reasons most prescribed fi res are set in the wet winter
season. However, plants and animals exhibit different
physiological and phenological conditions in different
seasons, and as a result prescribed fi res may not have
the same effects and impacts as natural fi res. For
instance, birds nesting in spring are more susceptible
to prescribed than to natural fi re, and there is much
evidence of varying plant regeneration responses to
prescribed fi res in differing seasons (e.g. Keeley 2006).
• Mediterranean climate and landscapes are very
attractive to humans, and are among the most popu-
lated ecosystems on Earth, and the most visited by
tourists. In most MCRs, people colonize landscapes in
11.3
PERSPECTIVES
Major challenges for woodland and shrubland restora-
tion in Mediterranean climate regions must be con-
fronted in the coming decades. Some of these relate to
previously identifi ed, but still poorly implemented,
needs that have emerged in the course of maturing
restoration theory and practice, such as project evalu-
ation and social involvement. Other research and
development horizons relate to new and, above all,
rapidly changing climate scenarios in the non-
analogue
Anthropocene Era
we are now entering.
For example, restoring sustainable fi re regimes, while
