2 Genetic Resources: Status, Development,
Losses, and Conservation Management
This chapter highlights the state and development of the world's genetic diversity
centers, differentiated according to biodiversity in general and agrobiodiversity in
particular. The extent and determinants of genetic extinction will be analyzed, and
the differentiation between biodiversity and agrobiodiversity is discussed. In the
last section, the methods for PGRFA conservation will be introduced.
2.1
State and Development of the World's Genetic Diversity
Centers
There is a wide variation in the estimation of the overall amount of existing
species or organisms: depending on different methodologies, the estimations lie
between 5 million species (Stork, 1993) and more than 360 million species (Andre
et aI., 1994). This variation is determined by the limited knowledge about
animals; especially as regards insects, the richest and most diverse group (Wilson,
1992), whereas the numbers of mammals and birds are fairly well known (Reid et
aI., 1993). The knowledge of the diversity of vascular plants is, however,
relatively comprehensive, even though plants have not been inventoried as well as
mammals or birds (Groombridge, 1992).
The inventoried plant species are not evenly distributed over the earth.
According to OEeD, (1996b) biodiversity - characterized as species richness -
tends to be higher in: (l) warmer regions than in colder ones; (2) wetter regions
than in drier zones; (3) less seasonal areas than in seasonal areas; and (4) areas
with more varied topography and climate than more uniformed areas.
The differences in the distribution of plant biodiversity emphasize the
importance of tropical and subtropical regions (especially tropical forests), and
underline the significance of developing countries in terms of conservation and
supply of plant genetic resources. Table 2.1 shows that regions dominated by
developing countries, i.e., South America, Africa, and Asia, host high numbers of
plants, whereas industrialized countries, e.g, European and North American
countries, contain less than 5% of all documented plant species. South America,
where nearly 30% of all higher plant species are to be found, is the most
biodiverse region for higher plants, if biodiversity is defined simply by species
richness.
Losses, and Conservation Management
This chapter highlights the state and development of the world's genetic diversity
centers, differentiated according to biodiversity in general and agrobiodiversity in
particular. The extent and determinants of genetic extinction will be analyzed, and
the differentiation between biodiversity and agrobiodiversity is discussed. In the
last section, the methods for PGRFA conservation will be introduced.
2.1
State and Development of the World's Genetic Diversity
Centers
There is a wide variation in the estimation of the overall amount of existing
species or organisms: depending on different methodologies, the estimations lie
between 5 million species (Stork, 1993) and more than 360 million species (Andre
et aI., 1994). This variation is determined by the limited knowledge about
animals; especially as regards insects, the richest and most diverse group (Wilson,
1992), whereas the numbers of mammals and birds are fairly well known (Reid et
aI., 1993). The knowledge of the diversity of vascular plants is, however,
relatively comprehensive, even though plants have not been inventoried as well as
mammals or birds (Groombridge, 1992).
The inventoried plant species are not evenly distributed over the earth.
According to OEeD, (1996b) biodiversity - characterized as species richness -
tends to be higher in: (l) warmer regions than in colder ones; (2) wetter regions
than in drier zones; (3) less seasonal areas than in seasonal areas; and (4) areas
with more varied topography and climate than more uniformed areas.
The differences in the distribution of plant biodiversity emphasize the
importance of tropical and subtropical regions (especially tropical forests), and
underline the significance of developing countries in terms of conservation and
supply of plant genetic resources. Table 2.1 shows that regions dominated by
developing countries, i.e., South America, Africa, and Asia, host high numbers of
plants, whereas industrialized countries, e.g, European and North American
countries, contain less than 5% of all documented plant species. South America,
where nearly 30% of all higher plant species are to be found, is the most
biodiverse region for higher plants, if biodiversity is defined simply by species
richness.