Conservation and Sustainable Use of the Biosphere - WBGU

18 C The biosphere-centred network of interrelations
them interact directly. In this context the term ‘interaction’
should not be understood in purely mechanical
terms; much rather the following patterns are
meant: Trend A and Trend B occur jointly in a region
in which environmental degradation can be seen. In
many cases this is an outcome of a clear causal relationship
between cause and effect, but can also only
be a weak indirect link merely indicative of a more
deep-seated cause of the coincidence.
Fig. C 1.2-1 illustrates this dynamic network. Especially
important interactions primarily affect the two
trends damage to ecosystem structures and functions
and genetic and species loss. Both of these trends correlate
with each other and can also mutually amplify
each other to the extent that in an extreme case the
ecosystem collapses and is replaced by another
ecosystem (Section D 2.4). Direct impacts on both
trends emanate from the ‘primary’ causes: the conversion,
fragmentation and substance overload of
natural ecosystems, introduction of species and
overuse. Conversion is especially serious because it
not only leads to species loss, but also reduces the
sink effect of natural ecosystems and strengthens
biospheric sources of greenhouse gases as CO 2
or
CH 4
(WBGU, 1998b). The above-mentioned close
correlation between conversion and fragmentation is
illustrated by a correspondingly strong interaction.
Fragmentation and isolation generally lead to
genetic and species loss in the natural ecosystem as a
result of population-biological processes (Loeschke
et al, 1994). The species diversity of the cultivated
landscape that developed after conversion and fragmentation
may even increase as a result of the higher
number of ecosystem types, but the biological diversity
of the original ecosystem type decreases (for
example, this applies to Central Europe in the post-
Ice Age; Section E 2.1). The increase in the anthropogenic
introduction of species can exert a devastating
influence on the structure of the natural ecosystems
concerned if the introduced species encounters
a high number of resources with only a few biological
‘opponents’ (eg competitors, predators, parasites).
Direct or indirect genetic and species loss can ensue
(Section E 3.6).
C 1.3
Impact loops in the biosphere-centred network of
interrelations of global change
The relationships within the biosphere outlined
above shape a large proportion of its dynamics. However,
the biosphere is also linked to the other spheres
of global change: trends from the hydrosphere or
industry, for example, also affect the biosphere and
trigger chains of action there that can amplify the
degradation trends in the biosphere. These more
deep-seated driving forces are described here.
If we imagine the plethora of worldwide changes
within the context of global change, then, surprisingly,
there are relatively few, but important, trends
that have an effect on the biosphere from ‘outside’.
We can image the complexity of individual examples
of biosphere damage by marking these important
trends and clarifying their connections by means of
amplifying or attenuating arrows. In this respect,
characteristic chains of action can be recognized, ie
trends linked by arrows that represent sequences in a
Loss of biospheric
sinks
Increase of anthropogenic
introduction of species
Substance overload of
natural ecosystems
Fragmentation of
natural ecosystems
Reinforcement of
biospheric sources
BIOSPHERE
Resistance formation
Overexploitation of
biological resources
Conversion of
natural ecosystems
Figure C 1.2-1
Trends and their interactions
within the biosphere. Thick
arrows show especially
important interactions.
Source: WBGU
Damage to ecosystem
structure and function
Genetic and
species loss