The Sperrgebiet, or forbidden territory, lies in the south-western corner of Namibia. Famous for its diamonds, the area is bordered by the Orange river in the south and the Atlantic Ocean to the west. The northern boundary was established at the 26°S line of latitude, whereas the eastern boundary parallels the coast c.100 km inland. The IBA includes the Namibian side of the Orange river mouth (adjacent to IBA ZA030). Largely uninhabited, the only towns in the Sperrgebiet are Oranjemund on the southern coast and Lüderitz on the northern coast. The Sperrgebiet is an extremely arid zone, encompassing the northern extremity of the winter-rainfall portion of the Namib desert. It is the windiest region in southern Africa. The only permanent water in the area is the perennial Orange river. The northern coastal plain is rocky and holds various sandy bays; the southern shores, intensively mined for diamonds, are reconstituted sandy beaches. The major part of the remaining area comprises sand and gravel-plains with low isolated hills. In the centre and north of the park, dune sand and sand-sheets predominate, the most prominent area being Obib dune-field which rises to 500 m. Several rocky ranges, low mountains and inselbergs are found scattered throughout the park.Various vegetation-types are found, including coastal zone vegetation, which consists of hummocks in sandy areas, which stabilize dunes and form barriers to sand movement. Lichens, such as Xanthoria, are found on the numerous rocky outcrops and on dead Salsola plants. The central sand-plains lie between 300 and 600 m and are covered by dune fields and coarse sands that are driven inland by southerly prevailing winds, which are a dominant feature of this region. The more elevated eastern sand-plains consist predominantly of gravel-plains with one permanent dune system north-east of the Klinghardtberg. The rocky outcrops and inselbergs receive higher precipitation and more fog moisture and have a more diverse flora than the surrounding areas. The Aurusberg supports the highest diversity and density of plants in the Sperrgebiet. The linear Orange river in the south supports dense riverine woodland.
See Box and Tables 2 and 3 for key species. This extremely arid area holds a depauperate avifauna of only some 110 bird species, many of which are restricted to the Namib–Karoo biome. However, the inclusion of the Orange river mouth boosts the species total to 251 bird species. The recently recognized Certhilauda barlowi is virtually restricted to the Sperrgebiet, which holds over 80% of its tiny 18,000 km² range. The newly recognized Certhilauda curvirostris just occurs in this region, in low numbers. Haliaeetus vocifer is common along the Orange river, where Phragmacia substriata and Francolinus capensis reach the northern limit of their distributions. The Orange river mouth is particularly species-rich (64 wetland species) and in the past has been the sixth most important wetland (for total abundance: 26,000 birds) in southern Africa. It is one of Namibia’s four Ramsar Sites. Bird numbers and species richness increase along its length from east to west, and the mouth alone holds four times as many birds as the total river along the Namibian border.Several characteristic species of the Namib–Karoo biome occur in the Sperrgebiet, including Eupodotis vigorsii, Eremopterix australis, Cercomela schlegelii, C. sinuata, Euryptila subcinnamomea and Sylvia layardi. Other arid-zone species which are found within the area include Neotis ludwigii, Certhilauda erythrochlamys, Ammomanes grayi, Eremalauda starki, Cercomela tractrac and Serinus alario.
Non-bird biodiversity: The Sperrgebiet is characterized by high levels of endemicity in various taxa. At least 45 plant species are endemic to the Sperrgebiet and thus Namibia, but many more are endemic to the Sperrgebiet and Richtersveld of South Africa. The coastal zone holds the spectacular endemic plant Sarcocaulon patersonii. Aurusberg holds several endemic plants that are exclusive to this peak. In the Orange river valley, the inselbergs Skilpadberg and Swartkop hold several plants endemic to the lower Orange river, including Aloe ramosissima (VU) and A. gariepensis. Endemic and near-endemic amphibians include Breviceps macrops, B. namaquensis, Strongylopus springbokensis and a recently discovered, and as yet undescribed, toad Bufo. Endemic and near-endemic reptiles include Homopus sp., Bitis schneideri, B. xeropaga and two legless burrowing skinks. The Sperrgebiet comprises about 40% of the global range of the small mammal Bathyergus janetta. Cephalorhynchus heavisidii (DD), endemic to the south-west coast of Africa and probably one of the world’s rarest dolphins, is fairly common off the Sperrgebiet coast.
Pressure/threats to key biodiversity
Wildlife in the Sperrgebiet is unofficially protected by virtue of the high security surrounding the diamonds mined there. The area is earmarked to become a protected area under the auspices of the Ministry of Environment and Tourism. It is adjacent to the large Namib-Naukluft Park, which lies to the north, and it is also narrowly linked to the recently proclaimed Huns-Ai-Ais Game Reserve in the east at Sendelingsdrift. To the south-east, across the Orange river, is the Richtersveld National Park in South Africa. This park shares the lower Orange river as a common boundary for several kilometres. The scenic value of this area has the potential to make an important contribution to the local and national economy. The only permanent water supply in the area is the Orange river, but flow rates have dwindled and will do so in future as the Lesotho Highlands Scheme takes more from the headwaters in Lesotho for water-supply to South Africa’s Gauteng District. Agricultural potential along the lower Orange river is minimal, and difficult to realize because of the great distance from suitable markets and the anticipated reduction of available water in the river. Nevertheless, organophosphates constantly filter into the river from lucerne farming on the river’s banks and may be detrimental to the associated flora and fauna.The area is largely used for diamond prospecting and mining by NAMDEB; the remainder of the area falls under the jurisdiction of the Ministry of Mines and Energy, which intends to maintain the high security of the entire Sperrgebiet by restricting access to the area and thereby limiting human impacts in the region. All mining activities should be undertaken in conjunction with Environmental Impact Assessment procedures. Mining activities should be restricted because mined areas require rehabilitation, and the massive quantities of waste generated by mining should be appropriately managed. The Ministry of Environment and Tourism has proposed that the area be converted into a park, to create a continuous strip of protected land between the Cunene and Orange rivers, under its jurisdiction. The Ministry of Mines and Energy has recently opened up 46 concessions along a 3-km-wide strip of the Orange river. The vegetation of the Sperrgebiet is for the most part pristine. The main terrestrial impacts on this area occur for 100 km along the coast and about 3 km inland from the town of Oranjemund. The intensity of the mining appears to have affected both shorebird numbers using the beaches and the number of breeding Sterna balaenarum on the coastal plains. Older mining concessions occur around Lüderitz, and along the eastern margin of the area where emergency grazing has been permitted since the 1950s. The Sperrgebiet has the distinction of supporting more non-native mammals than any other area of Namibia. Feral donkeys, European rabbits Oryctolagus cuniculus and house mice Mus musculus are among the aliens here, but ranges are restricted by the severe environment outside the winter-rainfall area. Offshore stocks of the fish Jasus lalandi have been severely over-exploited in the last 30 years and may be affected by the suction-dredging techniques of marine diamond-mining currently being employed.