Nama Karoo Biome occurs on the central plateau of the western half
of South Africa, at altitudes between 500 and 2000m, with most of
the biome failing between 1000 and 1400m. It is the second-largest
biome in the region.
The geology underlying the biome is varied, as the distribution
of this biome is determined primarily by rainfall. The rain falls
in summer, and varies between 100 and 520mm per year. This also
determines the predominant soil type - over 80% of the area is covered
by a lime-rich, weakly developed soil over rock. Although less than
5% of rain reaches the rivers, the high erodibility of soils poses
a major problem where overgrazing occurs.
The dominant vegetation is a grassy, dwarf shrubland. Grasses tend
to be more common in depressions and on sandy soils, and less abundant
on clayey soils. Grazing rapidly increases the relative abundance
of shrubs. Most of the grasses are of the C4 type and, like the
shrubs, are deciduous in response to rainfall events.
The amount and nature of the fuel load is insufficient to carry
fires and fires are rare within the biome. The large historical
herds of Springbok and other game no longer exist. Like the many
bird species in the area - mainly larks - the game was probably
nomadic between patches of rainfall events within the biome. The
Brown Locust and Karoo Caterpillar exhibit eruptions under similarly
favourable, local rainfall events, and attract large numbers of
bird and mammal predators.
Less than 1% of the biome is conserved in formal areas. The Prickly
Pear Opuntia aurantiaca and Mesquite Prosopis glandulosa
are the major alien invader species. Urbanization and agriculture
are minimal, and irrigation is confined to the Orange River valley
and some pans. Most of the land is used for grazing, by sheep (for
mutton, wool and pelts) and goats, which can be commensurate with
conservation. However, under conditions of overgrazing, many indigenous
species may proliferate, including Threethorn Rhigozum trichotomum,
Bitterbos Chrysocoma ciliata and Sweet Thorn Acacia karroo,
and many grasses and other palatable species may be lost. There
are very few rare or Red Data Book plant species in the Nama Karoo
Tourism potential is low. Mining is important in the Biome.
Most of the research into the dynamics of the biome has been done
in the east of the region, with the Grootfontein Agricultural Station
at Middelburg featuring prominently. Consequently, little research
in the west of the biome has been undertaken.