Conservation and Sustainable Use of the Biosphere - WBGU

Human use of species: the higher plants D 1.3
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area covered by a country: USA), the type and frequency
of successional disturbances (eg fire) and the
biological environment that promotes the establishment
of mutations and speciation (eg the specialized
pollination mechanisms of orchids). And, of course,
our level of knowledge also plays a major role.
D 1.3
Human use of species: the higher plants
If we take the approx 270,000 plant species that have
been described worldwide, then each of these has a
very different significance for humankind. If the
plants are usable then this provides the essential
incentive for efforts to maintain these species in a
world that is being used to an ever greater extent by
people. Therefore, in the following presentation, we
shall attempt to categorize plants according to the
various forms of use to which they have been put
(Fig. D 1.3-1).
D 1.3.1
Plant species used
D 1.3.1.1
Food plants
A large number of the some 3,000 plant species that
are used for human nutrition have been cultivated by
humanity. Of that number, 150 are significant in
terms of global trade, but just 20 species account for
approx 90 per cent of our total food consumption.
Just three important crops – wheat, rice and maize –
meet 60 per cent of calorie and protein needs
(Hawksworth and Kalin-Arroyo, 1995). It is
assumed, however, that 75,000 species are edible
(Myers, 1997).
Each of these species contains a host of different
strains or varieties that are related in different ways
to wild species. In the case of rice, two species are cultivated
(Oryza sativa and O. glaberrima) but a full
100,000 varieties of the first are known, then there
are 20 closely related wild forms from the same
genus, and an additional 71 closely related grass
species (Vaughan and Chang, 1995). Securing varietal
diversity must therefore be the primary concern in
order to maintain this genetic pool from which
breeders can draw for future use (Sections D 1.3.3.2
and I 1.2). In the long term, these genetic resources
may be best protected in-situ. collection and conservation
of these resources in gene banks only covers
an extremely small portion of the entire genetic variability
– and so, in the long term, it is much too risky
a strategy. This important issue will be dealt with in
detail in Section D 3.4. Closely linked to that issue
are legal questions that need to be clarified in the
context of international agreements (Section I 3).
D 1.3.1.2
Medicinal and poisonous plants and drugs
Around 120 active substances from 90 plant species
are used worldwide in medicines (WCMC, 1992).
This represents however just the use of plant substances
for medical purposes in industrialized countries.
In developing countries, where traditional medicines
play an important role, the figures are far
higher. The pharmaceutical ingredients are rarely
identical to the original natural substance; rather
they are derivatives that are prepared in in-vitro settings
(organic synthesis, fermentation) and in the vast
majority of cases without regular recourse to the natural
biomass of origin. A total of 25,000 plant species
are probably used worldwide for medicinal purposes;
75 per cent of all medications are plant-based
(Hawksworth and Kalin-Arroyo, 1995). Use can
however promote the extinction of the species: in
Central Europe alone the viability up to 150 plant
species is threatened as a result of intensive collection
(Hansen, 1999).
D 1.3.1.3
Construction, furniture, industry and fuel wood
Here the border between use and non-use is blurred
because one can fashion a ‘hut’ or particle board out
of almost any woody, that is ligneous, plant. Uses of
woody plants were far more diverse in previous centuries
(Box D 1.3-1). It is hard to estimate or quantify
such usage, and almost impossible if we include fire
wood and the so-called ‘non-timber forest products’.
In Germany, 112 species of wood are available commercially
(Sell, 1997). The nomenclature of the
known timber species by Bärner (1942) includes
13,000 species. If wood became in short supply, however,
other species could be used. And of course we
must not forget the some 600 species that are used for
rattan furniture, which draw almost exclusively on
natural stocks (WCMC, 1992; WBGU, 1998a).
D 1.3.1.4
Fibrous plants, dye plants, industrial plants
Despite the synthesis of many artificial substances,
humankind is still dependent on a number of plants
for the manufacture of fibres. The importance of