The southern section of the Cederberg–Koue Bokkeveld Complex begins at the Groot Winterhoek Wilderness Area, with its eastern boundary running north along the Ceres–Op-die-Berg road and then turning east to Katbakkies to join the road running north from Karoopoort to Calvinia. Farms along the Karoopoort–Calvinia road form the continuation of the IBA’s eastern boundary. The Ceres District’s borders with the Northern Cape, the Clanwilliam District and the northern border of the Cederberg Wilderness Area form the IBA’s northern boundary. Its western boundary is the N7 national road between Clanwilliam and Citrusdal; from the latter town the western boundary continues along the border between the Ceres and Piketberg magisterial districts. In the extreme south-west, the IBA borders the Groot Winterhoek Wilderness Area.
In the north, the Cederberg lies close to the northern limit of the Cape Fold Mountains. The northwest-trending Cederberg range is about 90 km long by 25 km wide and rises steeply above the Olifants River valley (at 170 m a.s.l.). Citrusdal, also at about 170 m a.s.l., is barely 17 km from Sneeuberg (2 027 m a.s.l.), which is the highest peak in the range. The Cederberg 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 Cederberg Wilderness Area, the Koue Bokkeveld and Groot Winterhoek mountains are the continuation of this chain. The Koue Bokkeveld is less rugged than the Cederberg, with only a few major peaks on its eastern flank at Heksberg (1 800 m a.s.l.) and Drie Koppe (1 780 m a.s.l.). The Olifants River lies in the deep gorge separating the Koue Bokkeveld from the Groot Winterhoek. The rugged Groot Winterhoek range rises sharply from the surrounding agricultural lowlands and encompasses the Groot Winterhoek peak (2 078 m a.s.l.) and the Sneeugat peak (1 884 m a.s.l.).
All the mountains in this IBA consist almost entirely of sedimentary Table Mountain Sandstone. In the more xeric eastern section of these mountains, the Skurweberg and Swartruggens hold an arid type of transitional flora between fynbos and karroid scrub; this mountainous arm stretches eastward into the karroid plains of the Ceres District. The mountains suddenly drop away to form the Tankwa and Doring river valleys, which erode their way through the flat, open Bokkeveld Shale landscape at an altitude of approximately 400–500 m a.s.l. The entire region experiences varying amounts of winter rainfall. The high-altitude, mountainous areas of the Cederberg and Koue Bokkeveld each receive at least 1 000 mm p.a., while the Groot Winterhoek to the south receives up to 1 600 mm p.a. There are local gradients in precipitation; at lower altitudes in the Cederberg, for example, the annual rainfall drops to below 400 mm. East of the Swartruggens, mountains enclosing the Tanqwa and Doring river valleys cut off the rain to the extent that the whole area receives, on average, less than 150 mm p.a. There are some extremely important rivers in this IBA, including most of the headwaters and catchment of the Olifants River system. The Olifants River estuary (SA099) forms an additional site of conservation significance for birds.
The remarkable variation in edaphic factors, including underlying soil structure and rainfall, leads to an extremely diverse flora, with mesic mountain fynbos grading into xeric succulent Karoo. The climate is one of extremes, with temperatures ranging from -6 °C, with snow and ice on some high-altitude peaks in winter, to over 46 °C on the karroid plains in summer.
The mountain fynbos found at higher altitudes in the Cederberg, Koue Bokkeveld and Groot Winterhoek ranges is dominated by a multitude of fynbos communities, with the Proteaceae, Ericaceae and Restionaceae as the primary constituents in the mesic south. The northern Cederberg holds more xeric communities, while the high peaks above 1 800 m a.s.l. typically hold alti-montane vegetation. 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. Belts of riverine vegetation, which line the mostly dry riverbeds, are dominated by Vachellia (formerly Acacia) karroo and create a network of well-wooded veins that stretch throughout the plains and gullies. Other habitats that occur within the IBA are constructed farm dams, human habitation, gardens and stands of exotic invasive alien plants.
SABAP2 indicates that a total of 235 bird species have been recorded for this IBA. The fynbos of the Cederberg–Koue Bokkeveld Complex and the surrounding karroid plains hold a remarkable number of distinct habitats, making them home to many bird species. The mountain fynbos holds Cape fynbos restricted-range and biome-restricted assemblage species such as Orange-breasted Sunbird Anthobaphes violacea, which is widespread among ericas; Cape Sugarbird Promerops cafer, which is almost restricted to the proteoid elements of fynbos; and Protea Seedeater Crithagra leucoptera, which is found in proteoid woodland and arid scrub at the base of the Cederberg. Cape Spurfowl Pternistis capensis, Cape Bulbul Pycnonotus capensis and Cape Siskin Crithagra totta are widespread in fynbos, while Victorin’s Warbler Cryptillas victorini is found in moist seeps in the hilly areas. Cape Rockjumper Chaetops frenatus is common on most rocky slopes above 1 000 m a.s.l. Although they have not yet been recorded this far north, there is a reasonable chance that both Striped Flufftail Sarothrura affinis and Hottentot Buttonquail Turnix hottentottus occur in low restioid cover and thick fynbos scrub.
The karroid vegetation of the Tankwa and Doring river valleys holds many Namib-Karoo biome-restricted assemblage birds and other arid-zone specials. The Ceres–Karoo lowland plains host Karoo Korhaan Eupodotis vigorsii, Southern Black Korhaan Afrotis afra, Spike-heeled Lark Chersomanes albofasciata, Large-billed Lark Galerida magnirostris, Karoo Lark Calendulauda albescens, Karoo Chat Cercomela schlegelii, Tractrac Chat C. tractrac, Karoo Eremomela Eremomela gregalis and Rufous-eared Warbler Malcorus pectoralis. Black-headed Canary Serinus alario occurs whenever seeding grass and water are available. During wetter periods Ludwig’s Bustard Neotis ludwigii, Namaqua Sandgrouse Pterocles namaqua and the nomadic Lark-like Bunting Emberiza impetuani and Black-eared Sparrow-lark Eremopterix australis move in.
The riverine acacia woodland holds Namaqua Warbler Phragmacia substriata, while the thicket and scrub on the slopes support Layard’s Tit-Babbler Sylvia layardi and Grey Tit Parus afer. The belts of riverine acacia woodland are of particular interest because they act as corridors along which many species are able to move in otherwise unsuitable terrain. Pale-winged Starling Onychognathus nabouroup and the scarce and elusive Cinnamon-breasted Warbler Euryptila subcinnamomea are common in rocky gorges and kloofs of the Koue Bokkeveld foothills. The newly described Karoo Long-billed Lark Certhilauda subcoronata occurs in rocky areas.
Other arid-zone species occurring within the IBA include Pale Chanting Goshawk Melierax canorus, Pririt Batis Batis pririt, Fairy Flycatcher Stenostira scita and White-throated Canary Crithagra albogularis. Both mesic and arid mountain areas and their associated cliffs occasionally hold Black Stork Ciconia nigra, while more common species include Booted Eagle Hieraaetus pennatus, Verreauxs’ Eagle Aquila verreauxii, Cape Eagle-Owl Bubo capensis, Ground Woodpecker Geocolaptes olivaceus and Peregrine Falcon Falco peregrinus. Martial Eagle Polemaetus bellicosus and Black Harrier Circus maurus are widespread residents, but rare across their range. Research has indicated that Verreauxs’ Eagle occurs in higher densities in this IBA than at other sites, although the breeding productivity of these birds is very low. The high densities illustrate the importance of the area to this species’ survival.
Globally threatened species are Martial Eagle, Black Harrier, Hottentot Buttonquail and Ludwig’s Bustard. Regionally threatened species are Verreauxs’ Eagle, Lanner Falcon Falco biarmicus, Black Stork and Cape Rockjumper.
Restricted-range and biome-restricted species that are common in this IBA include Cape Spurfowl, Cape Bulbul, Cape Sugarbird, Orange-breasted Sunbird, Karoo Chat and Layard’s Tit-Babbler. Locally common species meeting these criteria include Karoo Lark and Namaqua Warbler. Uncommon restricted-range and biome-restricted species include Ludwig’s Bustard, Karoo Long-billed Lark, Sickle-winged Chat Cercomela sinuata, Karoo Eremomela, Namaqua Warbler, Pale-winged Starling, Cinnamon-breasted Warbler, Black-headed Canary, Swee Waxbill Coccopygia melanotis, Cape Rockjumper, Protea Seedeater, Cape Siskin, Victorin’s Warbler and Hottentot Buttonquail.
Although the botanical description of this area is incomplete, the IBA contains both fynbos and succulent Karoo elements and is known to hold an exceptional number of plant species, many of which are endemic. Comprehensive botanical surveys will probably reveal more endemic species. The endangered Clanwilliam cedar Widdringtonia cedarbergensis occurs within the Cederberg Wilderness Area.
The Cederberg–Koue Bokkeveld Complex 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 the fiery redfin Barbus phlegethon, Twee River redfin B. erubescens, sawfin B. serra, Clanwilliam yellowfish B. capensis, Clanwilliam redfin B. calidus, Barnard’s rock catfish Austroglanis barnardi and Clanwilliam rock catfish A. gilli.
The global ranges of both the red adder Bitis rubida, described in 1997, and McLachlan’s girdled lizard Cordylus mclachlani are virtually restricted to the Tanqwa Karoo section of this IBA, while the Cederberg dwarf leaf-toed gecko Goggia hexapora and small-scaled leaf-toed gecko G. microlepidota are globally restricted to the IBA’s mountains. Several generally uncommon southern African endemics occur here, including the slender thread snake Leptotyphlops gracilior, common long-tailed seps Tetradactylus tetradactylus and short-legged seps T. seps, all of which have localised populations in the Tankwa Karoo. The southern rock lizard Australolacerta australis occurs only in this IBA and one other, the Boland Mountains (SA107). The Tradouw toadlet Capensibufo tradouwi breeds in moist depressions, vleis and springs in the Cape Fold Mountains and is found in the Cederberg and the Langeberg Mountains (SA103) IBAs.
The western sandveld lizard Nucras tessellata, dwarf plated lizard Cordylosaurus subtessellatus, Namaqua plated lizard Gerrhosaurus typicus, armadillo girdled lizard Cordylus cataphractus, Karoo girdled lizard C. polyzonus, graceful crag lizard Pseudocordylus capensis, southern spiny agama Agama hispida, marbled leaf-toed gecko Afrogecko porphyreus, giant ground gecko Chondrodactylus angulifer, striped dwarf leaf-toed gecko Goggia lineata, rough thick-toed gecko Pachydactylus rugosus and western spotted thick-toed gecko P. serval are all found within the Cedarberg–Koue Bokkeveld Complex.
Southern African endemics of more general occurrence include the Cape grysbok Raphicerus melanotis and reptiles such as the parrot-beaked tortoise Homopus areolatus, angulate tortoise Chersina angulata, black thread snake Leptotyphlops nigricans, spotted harlequin snake Homoroselaps lacteus, Sundevall’s shovel-snout Prosymna sundevallii, cross-marked grass snake Psammophis crucifer, Cape cobra Naja nivea, many-spotted snake Amplorhinus multimaculatus, berg adder Bitis atropos, Cape legless skink Acontias meleagris, red-sided skink Mabuya homalocephala, spotted sand lizard Pedioplanis lineoocellata, common mountain lizard Tropidosaura montana, Cape girdled lizard Cordylus cordylus, Cape crag lizard Pseudocordylus microlepidotus, southern rock agama Agama atra and ocellated thick-toed gecko Pachydactylus geitje. Threatened mammals include the leopard Panthera pardus, Cape gerbil Tatera afra, Cape spiny mouse Acomys subspinosus, Verreaux’s mouse Praomys verreauxii and aardwolf Proteles cristatus.
The expansion of agriculture and the indirect impacts of agricultural activities on the broader landscape (pollution, water abstraction, pesticide drift and the transformation of natural habitat) represent a major threat in this IBA. Habitat is being cleared in certain sections, particularly in the west around Pakhuis Pass and between Algeria and Clanwilliam, for the planting of crops such as rooibos and citrus fruit. Many of the river valleys, including the entire Olifants River valley and adjacent lower mountain slopes, have been transformed for agriculture. In general the higher mountain slopes, being difficult to plough, retain their fynbos or succulent Karoo vegetation. Some, however, are now being cleared for rooibos plantations. In addition to rooibos and citrus fruit, onions, potatoes, plums, apricots, peaches and berries are cultivated. Livestock is farmed in the eastern sections of the IBA and around Wupperthal towards the north-east. A shift from livestock farming to game ranching, particularly in the east, is also under way. This can help to rehabilitate indigenous habitat, but the increased fencing and the introduction of extra-limital game species can also negatively impact on biodiversity.
Agricultural activities can lead to modifications to the natural river and wetland areas to facilitate water abstraction. This is particularly prominent in the lower reaches of many of the rivers and mountain streams. High levels of water abstraction in this naturally arid area can result in a lowering of the water table, with associated knock-on impacts that are difficult to predict. Wetlands are also converted into farm dams to collect water for agriculture. Reserve managers estimate that approximately 50% of the smaller rivers are currently experiencing water abstraction levels that exceed the rivers’ ecological reserve and thus negatively impact on river biodiversity. The Clanwilliam Dam is due for expansion in 2015, which will lead to back-flooding and inundation of a larger area. The Olifants River upstream of the Clanwilliam Dam already runs dry in summer as a result of the high levels of abstraction.
Although not as serious a threat to this IBA as to others in the Cape Fold Mountains, alien invasive vegetation is present and can lead to habitat transformation. There are pine plantations around Zuurvlak, Citrusdal and Ceres as well as north of the Groot Winterhoek mountains and escapees from these plantations often spread out of control, especially in mountainous areas where it becomes difficult and costly to try to contain them. This can result in a landscape-level invasive alien plant problem. Alien trees are also known to accelerate river-bank erosion, reduce in-stream flow, cause changes in the fire regime and alter the composition of the soil and natural plant and animal communities. There is limited alien vegetation on the higher mountain slopes due to limited water availability. Pines Pinus species, gum trees Eucalyptus species, black wattle Acacia mearnsi and sesbania Sesbania punicea are present to some degree.
As in other fynbos habitats across the Cape Fold Mountains, changes to the natural fire regime have a negative impact on habitat quality in that they cause alterations to the composition and structure of the plant community. Managers estimate that approximately 70% of the Cederberg burned in 2013, while in the Groot Winterhoek area the average age of the veld is about four years. It is suggested, however, that changes to the fire regime are not as extreme here as in other Cape Fold Mountain IBAs due to the lower levels of human activity in this inaccessible area.
Additional threats impacting this IBA on a smaller scale include road-kills and the collision of birds with power-line infrastructure, the poaching of small game, wildflower harvesting, pollution resulting from agricultural activities and residential and commercial development. The characteristic Clanwilliam cedar is threatened throughout its range due to historical over-exploitation, too-frequent fires and climate change.
The Cederberg was proclaimed a mountain catchment area in 1897 and has been under State control for more than 100 years. Its change of status to a wilderness area in 1976 was based on the decline of the endemic and threatened Clanwilliam cedar. The Cederberg Wilderness Area (71 000 ha) was one of the first to be proclaimed, in accordance with the policy of the former Directorate of Forestry and Environmental Conservation (now under the control of DWAF) to extend reserves for more effective water management. Similarly, the Groot Winterhoek Wilderness Area (81 188 ha, comprising 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.
The IBA now includes the Cederberg Wilderness Area, the Matjies Rivier Nature Reserve and the Groot Winterhoek Wilderness Area – all proclaimed provincial nature reserves – as well as approximately 30 Biodiversity Stewardship sites that have been signed up as part of the CapeNature–GCBC Landscape Initiative. The remainder of the IBA is privately owned land and is utilised primarily for agriculture and ecotourism. Large parts of the IBA are inaccessible due to rugged mountainous terrain and the lack of road infrastructure.
The CapeNature–GCBC initiative has facilitated conservation awareness and networking activities among various partners in the IBA and, by helping to develop best-practice guidelines for the potato and rooibos industries, has benefited conservation. Plans are under way to engage the citrus industry in developing best-practice guidelines. The Biodiversity and Wine Initiative is also a role player in this IBA. Other conservation partnerships facilitated through the GCBC are the Twee Rivier Rehabilitation Project and the EWT’s Cape Critical Rivers Project, which focuses on the conservation of fish species in many of the Olifants–Doring tributaries in the IBA.
Within a reserve network, the Cederberg, Koue Bokkeveld and Groot Winterhoek mountains are the source of many of the freshwater systems in the Western Cape. These include a large portion of the Olifants River catchment, whose waters irrigate the arid lands in the west and flow to the Olifants’ mouth, the site of the Olifants River Estuary IBA (SA099). These mountains also support the Doring River, which runs through arid lowland along the eastern boundary of the IBA, and the Berg River in the south.
The GCFPA, in partnership with CapeNature, actively engages with most landowners in the IBA with regard to fire awareness, the fighting of fires and the development of fire-management plans. The Cederberg Conservancy comprises a number of landowners in the IBA who have made a significant contribution to conservation by formally agreeing to place much of their land under stewardship. These farms act as buffers or serve as extensions to parts of the Matjies Rivier Nature Reserve and Cederberg Wilderness Area. The detailed management plans for the nature reserves and stewardship sites will specify a number of conservation actions. These will include, but are not limited to: pro-active fire management by means of fire-breaks, prescribed burns and fire-reaction protocols; invasive alien eradication programmes, particularly in the Rodegat, Matjies, Krom and Twee rivers, which will be applied to vegetation as well as fish and mammal species in certain areas; infrastructure maintenance; biodiversity monitoring; law enforcement through regular patrols by CapeNature field rangers; and environmental awareness initiatives. Additional alien vegetation clearing programmes are active in the Matjies Rivier and Cederberg nature reserves and on some surrounding stewardship farms.
The Greater Cederberg Area lends itself to landscape-level research and various projects have been conducted or are active. These include predator research carried out by the Cape Leopard Trust and climate change studies conducted by the Centre for Invasive Biology. The South African Institute for Aquatic Biodiversity is actively engaged in a number of projects in some of the IBA’s rivers. Verreauxs’ Eagle research has been conducted recently throughout much of the IBA by UCT’s Percy Fitzpatrick Institute for African Ornithology and the Animal Demography Unit.
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