Wetland & Fish Ecology - Enviro Dynamics Namibia

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Environment altered, functions and processes cease permanently
Status:
Positive (benefit) or
Negative (cost)
Confidence in prediction:
High; Medium; Low.
Based on availability of information & specialist knowledge
Overall evaluation of significance of potential impacts:
SIGN: N/L/M/H
NONE:
No sign of impact at all
LOW: Localised/temporary – No amendment needed to proposed design
MEDIUM
HIGH:
Local/regional/short-term – Modify design or mitigate
High local or long-term or regional and beyond impacts.
No-go without mitigation.
These impacts are summed up in the attached Tables 5 to 14 and each deals with a
separate impact.
4.2 IMPACTS ON NUTRIENT AND ENERGY CYCLES:
(SEE TABLE 5)
With the exception of decades of work done by the University of Witwatersrand,
Rhodes University and the Okavango Research Institute of the University of Botswana
on how the Okavango Delta functions, succinctly summarised by Mendelsohn, van
der Post, Ramberg, Murray-Hudson, Wolski and Mospele (2010) little work has been
done on either nutrient or energy cycles in African floodplain wetlands and nothing
on the Cuvelai system. Thus only broad impacts based on how wetlands function in
general can be made. Wetland productivity depends on the plants and animals it
can sustain and how nutrients and energy is cycled between them. Generally a
healthy, undisturbed wetland will function better as it can support a diversity of
organisms each with its own role in maintaining the ecosystem, e.g. algae and plants
forming the basis of the food web with zooplankton i.e. the crustaceans and plants in
turn providing food to other aquatic creatures through several trophic levels up to
the top predators who in the Cuvelai wetlands are fish-eating birds and man. A
second important function of wetland vegetation and filter-feeding invertebrates is
water purification, they maintain the water quality.
To maintain a healthy wetland with efficient nutrient and energy cycles, care must
be taken to keep the system as natural as possible. The baseline study by Clarke
(1998a, 1998b, 1999,) fish studies by van der Waal (1991, 1999, 2000), on snails by
Curtis (1990, 1991, 1995a), aquatic invertebrates by Nakanwe (2009), frogs, by
Draft Environmental Impact Assessment: Oshakati Flood Mitigation Project
Specialist Study: Wetland Ecology and Fish Ecology Imputs
July 2012