Conservation and Sustainable Use of the Biosphere - WBGU

Introduction B
11
For example, how did life on Earth manage to regulate
the oxygen content of the atmosphere at exactly
21 per cent over hundreds of millions of years?
The dynamic equilibrium of the ecosphere that
was in balance for aeons is now at stake for the first
time – as a result of large-scale human intervention in
the composition and structure of the planetary biosphere.
One example of this is the ‘lungs’ of the biosphere,
ie the tropical rainforests in their entirety.
Since the onset of European colonization their total
area has been reduced by over 50 per cent, and the
inherent ability of most of the rest to function has
been weakened. As reported recently in the journal
Nature (Nepstad et al, 1999), the destruction is currently
progressing at double the pace assumed from
satellite images. In concrete terms this means that in
Amazonia alone, every year around 10,000–15,000
km 2 of rainforest are disappearing – in El Niño years
this rate may double as a result of deliberate and
accidental fires. As a consequence of this, the sophisticated
computers of the leading climate modelling
centres are spewing out a new worst case scenario: if
climate change resulting from anthropogenic greenhouse
gas emissions continues unabated, large areas
of the remaining tropical rainforests could collapse
towards the middle of the 21st century and thus signal
a new round in the galloping destabilization of
the Earth’s atmosphere (Cramer et al, 1999a).
Luckily, this is just hypothetical, albeit frightening,
conjecture, but a look at the current trends in the way
civilization is reconstructing the biosphere is hardly
less frightening: the background extinction rate is an
estimated 1–3 species per year (May et al, 1995).As a
result of human interventions this extinction process
has probably increased one thousandfold. The estimates
cited in the literature of the rates of humaninduced
species extinctions range from 1 to 130
species per day or from 1 to 9 per cent of the total
biota per decade. This needs to be seen against the
background of the fact that so far 1.75 million species
have been counted, but actually far more (20 million?)
exist/have existed in the biosphere. Since AD
1600 only approx 1,000 species extinctions have been
documented explicitly. But this figure is without a
doubt a great underestimation of the true extinction
dynamism that only proves how little we know about
our fellow creatures.
It is therefore completely legitimate to term the
pressure of civilization on species diversity as the ‘6th
Extinction’ in the history of life on Earth. The five
other major biospheric crises of the past (those of 440
million, 365 million, 225 million, 210 million and 65
million years ago) have played a key role in the
course of planetary evolution. The experts still argue
about the causes of the ‘Big Five’ – the reason for the
6th Extinction, which may even exceed its predecessors
in terms of impact and speed, is, however, solely
due to the dominance of a single species.
It is not only human-induced reductions in the
number of species that contribute to the rapid loss of
genetic diversity, but also the systematic loss of natural
hereditary genetic variation. This applies in particular
to the reduction of plant genetic resources in
agriculture. For example, in the last 15 years around
1,500 locally adapted rice varieties have become
extinct in Indonesia; in Sri Lanka around 75 per cent
of all rice varieties with relevance to agriculture are
descended from one parent plant (WRI et al, 1992).
These genetic and species losses are all the more serious
because they are irreversible processes: what is
lost remains lost, missed opportunities never return.
As far as the Earth’s landscapes are concerned, a
far-reaching conversion or degradation is taking
place across all habitat types.An illustration of this is
the fact that in California 90 per cent of all pre-
Columbian wetlands have now been lost and the situation
is not much different elsewhere in the world.
Whereas the area of the planet’s forests shrunk by
almost 20 per cent between 1700 and 1980, the area
of arable land grew by almost 500 per cent!
The intervention in the global metabolism of the
biosphere is no less dramatic: around 40 per cent of
the photosynthesis output of green plants is manipulated
by humans today; the CO 2
concentration of the
atmosphere, a prime parameter for the biosphere,
has already been increased by over 30 per cent by
anthropogenic processes; in nitrogen fixation and
freshwater consumption, the activities of the anthroposphere
now dominate the natural cycles. This is a
reconstruction of the pre-existing conditions into
which humankind stepped, not a mere adjustment.
In this report the Council will describe and explain
the reconstruction of the biosphere as a ‘project of
modernity’. The analysis will concentrate on the
three main pillars – species, landscapes, cycles. Furthermore,
it will identify the functional links among
these pillars, which also form the links among the different
time-space scales.To achieve this last objective
the Council will use its tried and tested systematic
interdisciplinary approaches.
WBGU reports always attempt to gain a holistic
view of the issue in question. It is not so much a case
of pure status and threat analysis, which is already
well documented in the scientific literature – and
would fill several volumes in the case of the biosphere.
Rather, the Council is primarily concerned
with answers to the question as to which national and
international measures represent adequate
responses to the objective diagnosis. In the case of
the modern transformation of the biosphere, such
measures are long overdue – however, they can only
be successful if they fit into the logic of a global