Environmental Engineering Reference
In-Depth Information
2007a). A wide range of effects is expected, some of
which already can be clearly noticed: (1) shifts in
species distributions, (2) often along elevation gradients,
(3) changes in timing of life history effects, (4) loss of
habitats (range contraction), (5) increase of diseases,
parasites and zoonoses (e.g. Lyme borrelioses and
plague) and (6) extinctions (Mawdsley
et al
. 2009 ). As
all these effects work out differently for different species,
it can also be expected that local communities might
change fundamentally and that differential movement
of species can potentially lead to novel combinations
with consequences for predator-prey and competitive
interactions (Stralberg
et al
. 2009). As the world gets
warmer, there will be a general tendency for species to
move or migrate towards the poles and to higher alti-
tudes. Conservation efforts may make use of this by
increasing the extent of protected areas or by establish-
ing protected area networks and corridors along eleva-
tional gradients to facilitate movements. For some
species, however, this will simply not be possible (polar
bear), while others will face physical barriers diffi cult
to overcome. In this situation, translocation can be
considered as is being done for two extinct British but-
terfl ies for which models predict that conditions have
suffi ciently improved that they can be reintroduced to
Britain (Carroll
et al
. 2009). But as current practices
may not be enough to avoid species loss, it has also
been contemplated to move species to sites where they
do not occur or have not been known to occur in recent
history, a process that is known as assisted colonization
or assisted migration (Hoegh-Guldberg
et al
. 2008 ).
Sympathetic as it may sound, this idea has met with
much criticism and strong arguments have been put
forward that it is not a good idea (Rubenstein
et al
.
2006). So is there an
uncertainty
how species will
respond, especially species that are understudied, while
also in the receiving community fundamental proc-
esses may have been altered (e.g. competition with
existing species), leading to profound changes in the
functioning of ecosystems. Needless to say, it is also
vital to increase the effectiveness of existing conserva-
tion measures and to do everything possible to
miti-
gate
the human - induced stressors.
Ecosystem dynamics with rapid shifting species
assemblages (see Chapter 21) makes reintroduction an
even more tricky endeavour than it already is. The very
high frequency of attempts, however, make clear that
people, somehow, also feel an urge to repair some of
the damage they have infl icted on ' wild ' nature, which
is a reason for hope.
