Nama Karoo Biome
occurs on the central plateau of the western half of
South Africa, at altitudes between 500 and 2,000m,
with most of the biome failing between 1 000 and
1,400m. It is the second-largest biome in the region
The Nama Karoo rain fails in summer, and varies
between 100 and 520 mm 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 meat, 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 Biome.
(Source: "The Vegetation of South
Africa, Lesotho and Swaziland", South Africa
Department of Environmental Affairs and