Conservation and Sustainable Use of the Biosphere - WBGU

36 D The use of genetic and species diversity
Box D 1.3-1
Use and substitution of ligneous plants in the
last 120 years
The following evaluation regarding the use and substitution
of woody plants is based on the analysis of an Italian book
from 1877 which describes in detail the use of woody plants
in Belluno and Trentino provinces (Soravia, 1877). In the
book, 63 woody species and genuses are addressed. These
are trees, shrubs and dwarf shrubs but for many of the
genuses there is no subdivision into species (eg in the case
of maple, linden, rose, blackberry). One can assume that this
book explores the entire woody flora of the area. Current
use has been compiled from various sources: Sell, 1997;
Frohne and Jensen, 1998; Teuscher, 1997 and Reif, 1983. It
should be noted that these are not limited to the restricted
locality described in the 1877 exploration.Thus, current uses
are overvalued.
In 1877 there were 94 forms of use for the 63 wood
species, dominated by medicinal extraction (52 species) and
followed by dyes (35 species) and fuel wood (32 species).
For lathe work, furniture construction, fodder and food
between 20 and 30 species were used, for ash production,
nectar sources for bees, barrel staves, tanning, house construction,
carving, shoe soles, birding, wagon wheels and
cogs between 10 and 20 species were used. For the remaining
species there were specialized uses, for example, the
dowsing rod could only be made of hazel.
Of the 94 forms of use, only 27 are still practised in 1999
(25 per cent), 14 additional local uses have been added and
it has not been taken into account that in more remote valleys
in Trentino the use of woody plants has remained more
diverse. 72 usable species over the course of the last 100
years have be substituted by the use of metals, plastics or
other materials. 20 species (19 per cent) switched use and
are today used as ornamental plants but in cultivated, not
wild forms. Around 30 to 52 of the earlier medicinal plants
are still used today in general medicine or natural remedies.
Six species in Germany are under protection in the red data
book, approx 25 species are used in landscape protection
and land reparcelling as natural hedges. The legendary
‘Ötzi’ carried over 17 wood species with him in the form of
tools, fuel and food when he died over 5,000 years ago
(Spindler, 1993).
fibres for textiles has decreased distinctly and there
are just a few species that are important in this
respect (cotton, coconut, sisal agave, hemp, flax, jute).
Far more important is the extraction of cellulose
from wood as a base substance for paper and cardboard.
Essentially, cellulose can be extracted from
almost all plant species, but there are only a few
dozen of the 30,000 world wood species that play a
significant role worldwide in industrial cellulose
extraction.
In addition, there are the species that are used to
extract dyes, oils, fats, resins and rubber, to produce
perfume substances, biogenic pesticides or other
products. For example, of the 600 eucalyptus species,
just 50 are cultivated for the extraction of essential
oils (Groeteke, 1998). In Germany, essential oils from
over 150 species are available commercially (Primavera
Life, 1999).
Over 5,000 species are probably involved worldwide.
This estimate must however remain rather
uncertain since most of the products are of only local
significance and are not traded internationally.
D 1.3.1.5
Species in support of ‘soft’ sustainability
It is well known in farming that plant monocultures
bring with them risks in terms of sustainability.This is
true both of the use of certain resources from the soil
and also with regard to parasitic attacks. It is only
with considerable inputs in the form of fertilizer and
pest control that intensively managed monocultures
can be maintained, otherwise within a foreseeable
period yields drop and it may become necessary to
abandon the site (Section E 3.3.4). Seen in that light,
mixed cropping is more sustainable than monocultures,
even if a small number of species is ultimately
used. This is the sense in which the term ‘soft’ sustainability
is used here.
In intensive agriculture mixed species are not
desired (‘weeds’), since these generally reduce yield.
In grazing systems, species diversity is sometimes
desirable since fodder composed of different species
is more digestible for ruminants. High protein content
in combination with a high fibre content can,
however, also be generated by mixing in artificial
fodder (fibre content: silage from maize, protein content:
soya), where the addition of particular amino
acids improves digestibility and fodder utilization. In
that case, the advantages of species diversity are substituted
by technical means and the cultivation of
suitable monocultures. Trade in fodder products is
important in this regard. The problems in using animal
products as fodder for ruminants were discussed
in the 1998 risk report (WBGU, 1998a).
In the case of perennial ligneous plants (forest)
the addition of non-crop species is more significant.
According to everything we know about the metabolic
cycles at work in forest ecosystems, a deciduous
mixed forest with several tree species and the associated
ground flora has greater sustainability than a
monoculture. Correspondingly, shade trees in tropical
cocoa and coffee plantations are important.There
are examples, however, where stocks with few species
grow sustainably for long periods. For example, the
boreal coniferous forests of the Canadian Shield are
dominated in large expanses by just one tree species