Conservation and Sustainable Use of the Biosphere - WBGU

150 E Diversity of landscapes and ecosystems
Box E 3.3-6
Forests and biological diversity
The loss of forest biodiversity results both from the loss of
forest land (Section E 3.3.4.4) and from the degradation of
existing forests. Both processes continue apace and, after
centuries of forest destruction in temperate and boreal
areas, since the mid-twentieth century they have taken
place particularly actively in the tropics. With regard to the
loss of biological diversity, special importance is attached to
the loss of tropical forests and forest degradation because
the tropical forests are disproportionately richer in species
than temperate and boreal forests and the agro-ecosystems
that result from the conversion are much more fragile.
The best contribution to the conservation of forest biological
diversity can be made by the biodiversity of forests
being understood as a carrier of biological resources. The
value of these biological resources comes to bear at various
levels, ranging from the household level (firewood, food,
medicine), local (food, firewood, medicine, building materials),
national (wood products, water, firewood, etc) and
international markets (wood products, resins, oils, tourism,
etc) (Section H 5). Forest biodiversity gains global significance
as an important carrier of information for future
options on technological or medical developments (Section
D 3.3). Further importance may be attached to the biodiversity
of forests regarding their stabilising effect on the
global climate (Section F 2). The importance of forests as
biological carbon sinks is currently the subject of international
discussion (WBGU, 1998b).
The information on the number of species in forests is
highly unreliable and fluctuates between 2 and 80 million
species. The mean value of the estimates is around 10 million
species, and it is assumed that the vast majority of these
are arthropods (WCMC, 1992; Heywood and Watson, 1995).
In turn, around 50–90 per cent of arthropods are to be found
in the tropical forests and this emphasizes their high fauna
diversity. With respect to plant biodiversity the much
quoted example form Borneo can be used, where 700 tree
species have been identified on 10 ha of forestland, in other
words more species than occur in the whole of North America
(Rodgers, 1996).
In light of the pressure on land use described above, further
losses of forests in the tropics will be inevitable (Chapter
G). The majority of the conversion will continue to be
for agricultural use. It is therefore all the more important to
integrate the land use changes into comprehensive concepts
that are anchored at regional level (Section E 3.9). The
maintenance of the agricultural productivity of the converted
forestland or increasing the productivity on existing
agricultural land must be an important objective (Section
E 3.3.4.2).
Although most national policies emphasize that the
remaining forestland should be protected, deforestation
continues on a global level. From this, it can be seen that the
causes of forest destruction are multi-faceted and differ
from region to region. Not only direct reasons, such as the
spread of slash and burn, but also indirect reasons due to the
failure of policies, such as rural poverty, lead to the continuing
destruction of forests (NNA, 1998; Jepma 1995; Pearce
and Moran, 1998; Chapter G).
Since the existing biological diversity of the forests cannot
be preserved as a whole and species are becoming
extinct more quickly than all the existing species can be
recorded (Pimm et al, 1995; Section D 1), special significance
is attached to the functional evaluation of biodiversity
alongside recording habitats. Two questions can be
asked:
• How much biodiversity is needed to conserve multifunctional
forests (Section E 3.3.9)?
• Can this question be answered on time?
The first steps along this route have been made with the
identification of hotspots of biodiversity, the designation of
indicator taxa and the mapping of the usage pressure on
existing forest ecosystems (Global Forest Watch; WRI,
1999).An accompanying measure that could help to reduce
the predatory exploitation of forest resources is the certification
of wood products and forms of management (Box
E 3.3). A legally binding regulation for forest protection is
long overdue (Section I 3.4.4). The instruments and means
of implementation currently available are, however, so limited
that it is extremely doubtful whether the dynamics of
the current trend can be decisively influenced.
be minimized, far-reaching changes in eating habits
and in the way we keep and use animals will have to
be effected.
• Overnutrition with foods of animal origin must be
reduced because it is inefficient on the one hand
and has a negative impact on health on the other.
• The productivity of domesticated animals should
be optimized because large unproductive stocks
have a disproportionate negative impact on biodiversity.
This should also include ‘improvement’ of
traditional livestock breeds.
• Grazing practices should be more oriented
towards the carrying capacity of the grasslands in
order to prevent the degradation of the grazing
areas.
Switching to animal foodstuffs from the sea is also
limited because some natural fish populations are
already being overexploited. Although aquaculture
is a possible alternative, high-quality feed must be
used, which – in turn – mostly comes from terrestrial
ecosystems. Also, establishing cultures of this kind in
lakes and shallow seas is problematic from the point
of view of environmental pollution and the impact on
the biodiversity of aquatic ecosystems (Section
E 3.4).
The production of food using biotechnological
methods has not yet progressed to a level where it
can relieve shortages. Although there is great potential
for the biological conversion of plant wastes or
residues into feedstuffs and foods, only a few
approaches have so far proved to be economically
sustainable. New information and conversion methods
should be developed for the better use of plant
biomass (such as wood or straw) as feed and food. In
this respect, molecular biological methods could
open up new opportunities.