ZA080
Cedarberg - Koue Bokkeveld complex


Year of compilation: 2001

Site description
The north-westerly trending Cedarberg mountains are c.90 km long by 25 km wide and rise steeply above the Olifants river valley (170 m). Citrusdal, at about 170 m, is barely 17 km from Sneeuberg (2,027 m), the highest peak in the range. The Cedarberg forms the northern spine of the watershed between the Olifants river to the west and the Tankwa-Doring river system to the east. Directly south of the Cedarberg Wilderness Area, the Koue Bokkeveld and Groot Winterhoek mountains are the continuation of this sandstone chain.

The flora is extremely diverse, with mesic mountain fynbos grading into xeric succulent Karoo. Species of the Proteaceae, Ericaceae and Restionaceae dominate the mesic south. The northern Cedarberg holds xerophytic communities on the slopes, while the highest peaks hold typical fynbos. Protea bushes are frequent. Widdringtonia woodland occurs in patches. Moving east, karroid vegetation begins to dominate, and in the flatter, low-altitude terrain of the Tankwa Karoo, varied dwarf succulent shrubland is dominated by Mesembryanthemaceae and seasonally by annuals and geophytes. The varied flora holds many succulents. The shrub layer includes Tetragonia, Pteronia, Rhus, Salsola and Lycium. Belts of riverine vegetation, which line the mostly dry riverbeds, are dominated by Acacia and create a network of well-wooded veins that stretch throughout the plains and gullies. Other habitats that occur within the site are constructed farm dams, human habitation, gardens and stands of non-native Eucalyptus and Populus trees.

Key biodiversity
See Box and Tables 2 and 3 for key species. The mountain fynbos holds all of the Cape Fynbos restricted-range and biome-restricted species. Nectarinia violacea is widespread in the ericas, while Promerops cafer is almost restricted to the proteoid elements and Serinus leucopterus is found in proteoid woodland and arid scrub at the base of the Cedarberg. Francolinus capensis, Pycnonotus capensis and Serinus totta are widespread within the fynbos, while Bradypterus victorini is found at moist seeps in the hilly areas. Chaetops frenatus is common on most rocky slopes above 1,000 m.

The karroid vegetation of the Tankwa and Doring river valleys also holds many Namib–Karoo biome-restricted assemblage birds and other arid-zone specials. The Ceres–Karoo lowland plains are good for Eupodotis vigorsii, E. afra, Chersomanes albofasciata, Galerida magnirostris, Certhilauda albescens, Cercomela schlegelii, C. tractrac, Eremomela gregalis and Malcorus pectoralis. The thickets of riverine Acacia woodland hold Phragmacia substriata and provide food, shelter and breeding habitat for Sylvia layardi and Parus afer. Onychognathus nabouroup and the scarce and elusive Euryptila subcinnamomea are common in rocky gorges and kloofs of the Koue Bokkeveld foothills.

Non-bird biodiversity: Although botanical description of this area is incomplete it is known to hold an exceptional number of plant species, many of which are endemic. The cedar Widdringtonia cedarbergensis (EN) occurs in the special Cedar Reserve within the Cedarberg Wilderness Area. The IBA holds most of the Olifants river catchment, which has a remarkable incidence of endemism among freshwater fish. It is one of only two river systems in southern Africa to have more than two taxa restricted to its catchment. All eight of the catchment’s endemic species are found in this IBA, including Barbus phlegethon (EN), B. erubescens (CR), B. serra (EN), B. capensis (VU), B. calidus (EN), Austroglanis barnardi (CR), A. gilli (VU) and Labeo seeberi (CR).

Among herptiles, both Bitis rubida, described in 1997, and Cordylus mclachlani (VU) have global ranges virtually restricted to the Tanqwa Karoo portion of this IBA. Goggia hexapora and G. microlepidota are globally restricted to the mountains of the IBA. Australolacerta australis occurs in only this IBA and one other, the Eastern False Bay mountains (IBA ZA086). Capensibufo tradouwi breeds in moist depressions, vleis and springs in Western Cape mountains and it is found in the Cedarberg and the Southern Langeberg mountains (IBA ZA092). Nucras tessellata, Cordylosaurus subtessellatus, Gerrhosaurus typicus (LR/nt), Cordylus cataphractus (VU), C. polyzonus, Pseudocordylus capensis, Agama hispida, Afrogecko porphyreus, Chondrodactylus angulifer, Goggia lineata, Pachydactylus rugosus and P. serval are all found within the Cedarberg–Koue Bokkeveld complex.



Pressure/threats to key biodiversity
The Cedarberg was proclaimed a Mountain Catchment Area in 1897 and it has been under state control for over 100 years. Its change of status to the Cedarberg Wilderness Area in 1976 was based on the decline of an endemic and threatened tree species, Widdringtonia cedarbergensis. It was one of the first proclaimed Wilderness Areas (71,000 ha), in accordance with the policy of the former Directorate of Forestry and Environmental Conservation (now under control of the Department of Water Affairs and Forestry (DWAF) to extend reserves for more effective water management. Similarly, the Groot Winterhoek Wilderness Area (81,188 ha; 30,369 ha State Forest and 50,819 ha private land) in the south-west was established for the sake of water conservation in 1981. These two areas support the majority of the catchments of the Berg and Olifants rivers, two of the Western Cape’s most important river systems.

Management objectives in all mountain catchment areas are similar. The prime goals are production of potable water and nature conservation, with fire-hazard reduction, wildflower harvesting, recreation and grazing being of lesser importance. In creating a reserve network, the Cedarberg, Koue Bokkeveld and Groot Winterhoek mountains form the source and lifeblood of many of the freshwater systems in the Western Cape, including a large portion of the Olifants river catchment, which irrigates the arid lands to the west; the mouth and estuary of this river form another IBA (IBA ZA078).Invasive non-native trees of Acacia, Hakea and Pinus pose a serious threat to the conservation of water and vegetation in these mountains. In places, these exotic taxa dominate thousands of hectares, significantly modifying natural communities and threatening many indigenous taxa with extinction. Alien trees are also known to accelerate riverbank erosion, reduce in-stream flow, cause changes in fire regime and alter the composition of the soil and natural plant and animal communities.

Alien taxa are now widespread, and the control of these elements is now the largest single task facing most managers in this biome. Bio-control agents, including fungus and insects, have been introduced to prevent the spread of alien species. Some of these agents have been extremely successful. The ingenious ‘Working for Water’ programme initiated by DWAF involves physical removal of alien plants in water-catchment areas. This increases water run-off and simultaneously employs people.


Recommended citation
BirdLife International (2020) Important Bird Areas factsheet: Cedarberg - Koue Bokkeveld complex. Downloaded from http://www.birdlife.org on 04/08/2020.