Biodiversity
Under the IUCN Red Data Book system, roan sable and tsessebe
are all classified as "Lower Risk (conservation dependent)"
by the Antelope Specialist Group (ASG 1998) and it is evident
from the distributional
data that these species cannot be regarded as threatened
in any global or regional context. All three species are of
conservation concern at the national level in Namibia because
their numbers are low and the various subpopulations making
up the national metapopulation are isolated from one another.
However, most
of the main body of the country is outside the limit of the
rainfall range in which the three species are found 'naturally'.
Although substantial populations of roan and sable (and, to
a lesser extent, tsessebe) have been built up on private land
in the main body of the country, it would be a mistake to
regard these as secure because of their permanent vulnerability
to rainfall regimes. Because the areas in which roan, sable
and tsessebe are found 'naturally' in northeastern Namibia
are spatially linked to larger populations in Botswana, they
would not qualify independently for any category of threat
based on population numbers.
The greatest danger to the Namibian populations of these
species is the potential
fragmentation which could arise if links were severed
with the Botswana population due to injudicious application
of veterinary control fencing or the spread of settlement
and subsistence agriculture in the north east of the country.
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If roan, sable and tsessebe were to disappear from their
former range in north-eastern Namibia where the rainfall conditions
are favourable, this would be a loss of biological diversity
and a failure of wildlife management. Their persistence in
viable numbers could be seen as an indicator of ecosystem
health.
Several factors threaten ecosystems in north-eastern Namibia
including the uncontrolled spread of human settlement, an
overabundance of cattle (with the attendant veterinary control
measures) and, perhaps greatest of the threats for roan, sable
and tsessebe, is the burgeoning
elephant population which is likely to modify their habitats
unacceptably.
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