Conservation and Sustainable Use of the Biosphere - WBGU

24 C The biosphere-centred network of interrelations
C 1.3.3
Impairment of the regulatory functions of the
biosphere
The role of the biosphere in the Earth System is not
limited to a passive anchoring in the physical framework
conditions of Planet Earth. Within certain limits
the biosphere is also actively involved in controlling
the environmental conditions (Section F 1).
Since there is no regulatory mechanism between
actual and ideal conditions with defined regulatory
parameters in nature, the homeostatic principle
comes into play here: a dynamic equilibrium of substances
comes into being as a result of a negative
feedback between contradictory principles, which,
for example, not only has a major influence on the
radiatively-active composition of the atmosphere,
but also on soil fertility or the water cycle. Ultimately,
practically all substance compositions of the environmental
media (soil, water, atmosphere) would probably
be greatly influenced by the biosphere and, possibly,
even ‘regulated’ via negative feedback (Section
F 5). The intensities of the biologically moderated
substance sinks and sources that have organized
themselves into practically stable dynamic equilibria
in the course of evolution are central to this. This
biosphere’s role is being increasingly disrupted by
human intervention (Section F 3). Here the two
trends of loss of biosphere sinks and reinforcement of
biospheric sources are the focus of analysis (Fig.
C 1.3-3).
Changes in biospheric climate regulation
The radiatively active cascade is an important biospheric
regulatory cycle, in which humankind intervenes
by means of the conversion of natural ecosystems
and an increasing overexploitation of biological
resources. As a result, on the one hand biological
sinks for anthropogenic carbon dioxide emissions are
lost, on the other hand carbon stored in the soil
(humus, dead biomass) and radiatively-active
methane are released (reinforcement of biospheric
sources). The greenhouse effect is further amplified
in conjunction with the worldwide trend of an
increasing consumption of fossil energy and the associated
rise in trace gases in the atmosphere.
This change in the atmosphere’s thermal balance,
which amplifies the trend of global and regional climate
change, leads, on the one hand, to a change in
the local water balance, on the other hand, direct
harmful effects can be seen in the biosphere. A
change not only in the air temperature, but also to the
water balance and, thus, to the groundwater level,
leads to damage to the ecosystem structure and function
if the ecosystem concerned has only low adaptability.This
obvious environmental damage is given a
high profile in the media and often brings about
renewed efforts to protect and conserve nature (Section
C 1.3.4). Growing environmental awareness, also
in conjunction with sensitization to global problems,
is, however, in stark contrast to growing demands and
the increasing spread of western patterns of consumption
and lifestyles. These trends are closely
linked to internationally significant developments,
such as increasing tourism (Section E 3.7), agricultural
expansion, growing traffic volumes and economic
globalization (Fig. C 1.3-4), which are usually
associated with heavy consumption of resources and
energy. In this way, as a result of the worldwide
appropriation of land, they amplify the loss of biosphere
sinks and thus modify biosphere climate regulation.
Disrupting the role of the biosphere in the
water cycle
The hydrological cycle is also largely influenced by
the biosphere. As well as an additional effect on the
climate via the large-scale movement of energy
towards the poles, the reduction of radiation through
clouds or the greenhouse gas effect of water vapour
in the atmosphere, the water cycle has important
additional aspects: it transports nutrients, creates the
conditions for the reduction of high solar radiation
by forming clouds and plays a major role in the global
energy balance. As a result of the conversion and the
substance overload of natural ecosystems, this fragile
equilibrium is being disrupted. Consequently the
water retention capacity or storage capabilities are
greatly impaired. On a larger scale, there is a loss of
biosphere sinks that encourages erosion processes
and morphological changes. In turn, this changes the
local water balance and thus, for example, the
groundwater level.
If certain levels are exceeded this impact loop can
feed back positively. One example of this is the
process of self-reinforcing desertification. The overuse
of soils that may already be marginal not only has
a direct influence on the biosphere, but also, almost
imperceptibly at the beginning, on the special functions
of the flora for the local water cycle. If the biologically-modified
water retention capacity is then
reduced, the ecosystem stability falls and minimal
changes in the climate or use can lead to a catastrophe.
C 1.3.4
Humankind as the preserver of nature
The negative ecosystem trends that can be observed
worldwide, such as the extinction of species, are