the role of tourism in natural resource management in the okavango ...

since the mid-1990s, with Namibia's proposed water extraction plans. Similar fears
are reflected in the common claim that the lack of high floodwaters during the past
two decades was due to the alleged construction of dams in Angola and the Caprivi
Strip (which are completely unfounded). However, fears of reduced and changed
patterns of flow, regardless of the cause, are indeed warranted as so much of the
river system's functioning depends on regular strong flows and flooding that, for
example, carries sediment into the Delta and enables fish to breed in floodplains.
The variety of habitats in the Delta is in fact directly the result of changing water
levels, mainly because different plant communities occupy different flood zones
(Mendelsohn and el Obeid, 2004).
The whole Okavango River system is characterised by low nutrient levels. Greater
levels of nutrients, for instance in the form of nitrogen and phosphorous fertilisers
washing out of large agricultural projects, would lead to more biological production,
particularly in the Delta where the extra nutrients would accumulate. Beds of
papyrus might expand, causing channels to close more quickly and rapid changes to
the distribution of water. It is also likely that the occurrence of Kariba weed (Salvinia
mo/esta) would increase. This could have severe impacts on the Delta, since the
weed forms dense mats covering large surface areas of calm water. The mats cause
a reduction in the water's oxygen content, which would have disastrous
consequences for all life in the Delta (Mendelsohn and el Obeid, 2004).
Higher levels of other chemicals such as calcium, magnesium, sodium and silica,
would probably accompany nutrient increases. In this case, a severe reduction in
papyrus could result from concentrations of these harmful solutes. Patterns of
sediment accumulation and the way in which water is distributed in the Delta could
change, habitat diversity may decline, and the Delta might gradually transform, in the
worst case scenario, from a freshwater to a saline wetland. Levels of pollution from
urban effluent and other sources are still too low in the Okavango to do any serious
harm, but every effort needs to be made to safeguard the river from these and other
toxic chemicals, such as pesticides. It is widely agreed that Botswana's use of
endosulphan to kill tsetse flies reduced fish stocks in the Delta between the 1970s
and the early 1990s (Mendelsohn and el Obeid, 2004).
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