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