Okavango Delta Management Plan - Ramsar Convention on Wetlands

3.2 BIO-PHYSICAL PLANNING ISSUES
Development planning in most human societies strives towards stability and predictability,
which in the case of the <strong>Okavango</strong> <strong>Delta</strong> is in direct conflict with its inherently unstable
nature. This is a major challenge for the management of ODRS.
3.2.1 ECOLOGICAL FUNCTIONS AND SERVICES
Gumbricht and McCarthy, 2002, have succinctly summarised the functioning of the
<strong>Okavango</strong> system by equating it to a physiological system. They have described it as
follows;
“The <strong>Okavango</strong> is a good example of a complex middle number geo-physiological system, which has many
similarities with physiological systems. The <strong>Okavango</strong> Wetland with its distributary channels is like the
bloodstream and lymphatic system, with fast turnover and transporting nutrients and other dissolved substances.
The Islands Mosaic is like the internal organs, processing the nutrients and energy, keeping the balance of the
“blood”. The Fan is the skeleton and the skin, the bodily envelope and backbone keeping the organs in place.
What comes in via the Panhandle is like the food intake. The superswell and the climate it fosters is the general
environment.”
The seasonal flooding is recharging the groundwater aquifers which also causes a high
biological production of wildlife and livestock as well as of veld products and fish.
The shifts in flooding patterns, the duration and extent creates a <strong>Delta</strong> that is much larger
than the annual flooded area; it provides fresh water to communities surrounding the <strong>Delta</strong>
and facilitates molapo farming.
Islands are important ecological function of the <strong>Delta</strong>, they create habitat mosaic which is
responsible for the high biodiversity that is found in the <strong>Delta</strong>. The resultat high habitat
diversity results in the internal ecological resilience of the <strong>Okavango</strong> <strong>Delta</strong> syste. Many
islands form as a result of the subsurface precipitation of calciste and armophous silica
which produces vertical expansion creating a topographic relief which is mainly due to
transpiration from trees in riparian fringes (McCarthy et al., 1993). This process has
resulted in the creation and growth of islands whereby salts are permanently removed from
water. This process does also concentrate the remaining salts to centrums of islands where
it sinks permanently to deep groundwater. These processes maintain the <strong>Delta</strong> as a fresh
water system. The <strong>Delta</strong> does permanently remove organic matter and nutrients from the
water and by that it is producing crystal clear waters of high quality.
3.2.2 BIODIVERSITY
The <strong>Okavango</strong> <strong>Delta</strong> features as one of the world’s important biodiversity areas. In
particular the numbers of plants, mammals, reptiles and birds are high (see Ch 2…..). This
is firstly because of the flood pulse without which the seasonal floodplains with its entire
flora and fauna would disappear, and the biological productivity would dramatically be
reduced. The second process is the shift in flood distribution and size over different time
scales. This creates a dynamic patch system of different nutrient levels and at different
stages of biological succession.
The major factor organizing the <strong>Delta</strong> habitats is the depth and duration of flooding. There
is a typical gradient from permanent waters (streams and lagoons) and swamps, seasonal
floodplains, occasional floodplains, riparian woodlands and dry woodlands. This pattern is
repeated across the <strong>Delta</strong> resulting in a mosaic landscape.
The habitat diversity is high and the habitat patches small causing a large edge effect
which favours species dependent on more than one habitat. The largest habitat diversity is
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