By Shirley Bethune and Kevin Roberts, Wetlands Working Group
The Etosha National Park is celebrating its centenary this year. Far older by millions of years is the natural phenomenon – the Etosha pan – that the park is named after. Clearly visible on satellite images, the shallow Etosha Pan is the largest of its kind in Namibia and one of the largest in Southern Africa.
In ecological terms, a pan is a shallow, ephemeral pool fed by local rainfall or runoff from ephemeral, endoreic rivers. Endoreic describes rivers that do not flow to the sea. Some of our best-known tourist destinations are a result of endoreic rivers – think of Etosha, Sossusvlei and Tsondabvlei in Namibia and the Okavango Delta and Magadigadi in Botswana. The dry pans form in shallow depressions, often with a clay base that is inundated irregularly for short periods. Many are saline due to the accumulation of salts left behind each time the water evaporates.
Fed by a complex, delta-like network of interlinked shallow channels and pans known as iishana (oshanas) in north-central Namibia, the Etosha Pan is dependent on seasonal floodwaters from the Cuvelai River rising in Angola. Water crosses into north-central Namibia through the Oshana Region via the Ekuma River and the Lake Oponono pans to the ‘bare place’, Etosha. The Cuvelai provides water and other resources such as fish, bullfrogs, Pyxicephalus adsperus and waterlily tubers, called omado. The sedges, bulrushes and reeds growing around an oshana provide materials for building, basketry and fishing gear. Each year the floodwaters spread over a large area to recharge groundwater and as the floods recede, leave fertile soils that provide pastures for livestock in the dry season. Deeper, excavated pools, called eendombe, can hold water for longer and are often surrounded by large trees bearing edible fruit, including birdplums or embe, from the Berchemia discolor tree, and jackalberries or eenyandi from the omwandi tree (Diosyros mespiliformis). These fruits are for sale at roadsides and markets, even as far south as Windhoek.
The earliest inhabitants of Etosha area were hunter-gathers, the Hai||om, who lived on the game and vegetation supported by irregular floods and local rainfall. Most years the seasonal floods through the network of iishana do not reach the Etosha Pan, seldom going beyond the pans of Lake Oponono. But, once every seven to ten years, an unusually large flood or efundja carries water all the way into the Etosha Pan, transforming the chalk-dry, saline desert into a spectacular wetland, teeming with birdlife, fishes and frogs.
Inland Ramsar Site
This miraculous transformation makes Etosha very special, earning its place as one of four Ramsar Sites or wetlands of international importance in Namibia. Since 1995, when Namibia designated its first four Ramsar Sites, Etosha has held the honour of being Namibia’s only inland Ramsar Site, managed according to the Wise-Use principles of the Convention on Wetlands of International Importance. It is well protected within a world–famous national park, but there is concern that its source waters in the Cuvelai do not enjoy the same degree of protection. To address this, the first of the Cuvelai Basin Management Committees, the Iishana Sub-basin Management Committee, was established in accordance with the new Water Act, to actively involve all stakeholders in the management of this important wetland and its water resources. A Polytechnic student is currently investigating the habitat preferences and the ecological, social and economic importance and conservation of bullfrogs, guided by the frog specialist at the Ministry of Environment and Tourism and supported by the Wetlands Working Group of Namibia.
Internationally, the Etosha National Park is listed as an Important Bird Area, because it supports significant numbers of Blue Cranes, which are globally threatened, and three globally near-threatened species, Lesser Flamingos, Pallid Harriers and Blackwinged Pratincoles. Etosha supports more than 1% of the world population of White Pelicans, Greater Flamingos, Chestnutbanded Plovers and Caspian Plovers. Twenty other bird species found in Etosha are either endemic to Namibia or have a restricted range. These include Hartlaub’s Fancolin, Ludwig’s Bustard, Rüppell’s Parrot, Bradfield’s and Monteiro’s Hornbill, Rockrunner, Whitetailed Shrike, Whitebellied Sunbird and Blackheaded Canary, making the park a choice destination for birders.
Unique vegetation zone
Like most pans, Etosha Pan supports very little vegetation, living up to its Oshiwambo name, meaning ‘bare place’. Very little grows alongside the pan. Botanists call this unique vegetation zone the Saline Desert and Dwarf Shrub Savanna Fringe. Typical salt-tolerant or halophytic dwarf shrubs found in this fringe include two saltbushes: Suaeda articulata, with its fleshy, reddish leaves, and Salsola etoshensis or ganna, a woody, grey shrub with papery flowers. Other interesting small shrubs are: Leucosphaera bainesii, a grey-green bush with woolly leaves and white flowers; Petalidium engleranum, with soft yellow flowers; and two species of Monechema – M. genistifolium, with blue-white flowers, and M. tonsum, with purple flowers. The main factor determining this vegetation type is the saline soil formed by the evaporation of Cuvelai floodwaters and sporadic rainfall.
Yet, on those occasions when the efundja reaches the pan and the water remains for a sufficiently long period, or good rains occur over the pan itself, the area can be transformed and may even support aquatic plants more commonly found in the iishana to the north. Then the pan teems with wetland birds and large bullfrogs, Pyxicephalus aspersus, while crustaceans appear as if from nowhere, making the most of the brief wet season, mating and laying eggs before the water dries out. Most years we can catch a glimpse of this abundance when the Omuramba Owambo floods Fischer’s Pan near Namutoni. Fossils found in Etosha recently confirm that the pan was once a great lake supporting wildlife typical of our perennial wetlands, such as sitatunga. Today we must content ourselves with a glimpse of that past verdant lake every decade or so, when the weather up north conspires to inundate the pan.
Even during the dry months, springs and seeps like Okerfontein, Salvadora, Homob and Okondeka that are fed by groundwater along the pan edge, provide water to large numbers of game. Careful observation shows that, given the opportunity, animals prefer to drink close to the eye of these springs, with elephants dominating, leaving the furthest, distinctly brackish, trickle to lowlier beasts.
Etosha Pan is currently our only inland Ramsar Site, but we have many more wetlands that potentially meet the Ramsar criteria to be recognised internationally as inland wetlands. One is the upper Cuvelai on which Etosha depends. Also under consideration are the lower Okavango River downstream of Mukwe as an extension of the largest inland Ramsar site in the world – the Okavango Delta; the Zambezi floodplains, including Lake Liambezi and the Linyanti swamp; and the Karst lakes and caves including Otjikoto Lake, Guinas Lake and the Dragon’s Breath cave. This year marking Etosha’s centenary is an ideal opportunity to consider designating the next Ramsar sites, starting with the Lake Oponono pans and the iishana of the Cuvelai system as an extension of the present site.
This article appeared in the 2007/8 edition of Conservation and the Environment in Namibia.