Located 50 km south of Johannesburg, Suikerbosrand lies between the towns of Heidelberg and Meyerton in Gauteng's industrialised Highveld. The reserve has been expanded in recent years by the addition of an extension northward to the R550 and east up to the N3. The new section includes a large area of grassland, wetlands along the Rietspruit and drainage lines. This extension is extremely valuable as it contains habitats suitable for African Grass Owl Tyto capensis and Secretarybird Sagittarius serpentarius.
The reserve is dominated by Suikerbos Ridge, which runs from west to east, rising from the surrounding plateau (1 500 m a.s.l.) to reach its greatest height (1 918 m a.s.l.) in the form of knolls on the central plateau east of Kareekloof. The ridge is broken by numerous seasonal streams, and the associated well-wooded kloofs and steep cliffs (varying in height from 15 to 45 m) contrast with the predominantly open grassy plains. Two important areas are the aloe forest near Kareekloof and, in the south-west, the vegetation community dominated by Vachellia (formerly Acacia) karroo trees.
Although the annual average is 700 mm, rainfall can vary considerably over short distances, with the most rain falling in the east and the least in the west. In addition, the ridge forms a divide, so that rain may fall to the north but not to the south and vice versa, further complicating local rain events. This steep rainfall gradient results in a wide variety of vegetation types occurring within the reserve. Sour grassveld dominates most of the area, although bushveld also occurs along the watercourses and in the east and south. Large parts of the foothills were once cultivated land but are now returning to their natural state.
The diversity of habitats in the reserve has resulted in more than 270 species being recorded in SABAP2. It is not certain how many White-bellied Korhaans Eupodotis senegalensis occur and further research is needed in order to obtain exact numbers. The inclusion of the extended area into the reserve has ensured that African Grass Owl remains listed as a key species. Counts produced 12 birds in 2007 and eight in 2014.
Melodius Lark Mirafra cheniana has been added as a key species because it has been reported regularly in this IBA since 2007. Up to 50 individuals have been recorded at one time.
Secretarybird breeds in the reserve and two pairs have been recorded here in recent years. Sentinel Rock Thrush Monticola explorator occurs in the east and Kalahari Scrub Robin Erythropygia paena, Red-headed Finch Amadina erythrocephala, Black-faced Waxbill Estrilda erythronotos and Violet-eared Waxbill Uraeginthus granatinus are regularly reported. Independent observers as well as those participating in SABAP2 have recorded Blue Korhaan Eupodotis caerulescens, Corn Crake Crex crex and African Marsh Harrier Circus ranivorus.
The globally threatened species that occur in this IBA are Melodious Lark, Blue Korhaan and Secretarybird (two pairs). Regionally threatened species are African Grass Owl (12–30 individuals) and White-bellied Korhaan. Kalahari Scrub Robin and White-bellied Sunbird Cinnyris talatala are the only biome-restricted species in this IBA.
To be updated.
The biggest immediate threats to this IBA are unplanned fires and uncontrolled grazing and trampling by cattle. Fire is an important tool for grassland management and the burning plan for the reserve takes into account the requirements not only of the veld and ungulate species, but also of the broader biodiversity. However, a lack of financial resources hampers efforts to secure the reserve against unplanned fires and illegal grazing, and these are a perennial problem. Incompatible fire and grazing regimes negatively affect the availability of suitable habitat for key bird species such as African Grass Owl and are thought to be the primary cause of local population declines in the northern extension.
A number of mining applications have been submitted for the extension and adjacent properties; if approved, they could have a severe negative impact on the key species in the IBA. A number of transmission lines traverse the IBA and could be a threat to large-bodied species such as Secretarybird. More monitoring is needed to determine whether they are indeed a threat.
Suikerbosrand was proclaimed a nature reserve in 1974 and initially comprised sections of nine farms, with a combined extent of 11 595 ha. Additional sections of six farms to the north of the original reserve were purchased between 2000 and 2006. The process of incorporating this extension into the main reserve has yet to be completed, but as of 2014 the proclaimed extent of the nature reserve has been expanded to 14 726 ha.
The reserve is managed by GDARD and is extremely important at a local level as it is one of the few areas in the southern Highveld where significant remnants of the original flora and fauna remain. Located within one of the most densely populated and industrialised regions in sub-Saharan Africa, Suikerbosrand is used intensively for environmental education, outdoor recreation and resource management.
Densities of almost all the larger wide-ranging birds in the area have been reduced as humans have increased and intensified their use of the land. A species such as Secretarybird had its density considerably reduced in Gauteng, while Cape Vulture Gyps coprotheres and Martial Eagle Polemaetus bellicosus are now rare species for this reserve and are seldom seen. Appropriate landscape management, including proactive awareness campaigns to prevent the persecution of large birds in the district, could result in the return of some of these wide-ranging raptors to the area. However, the reserve in isolation is probably too small to support viable populations of any of the larger wide-ranging birds.
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Bredenkamp GJ, Theron GK. 1980. A synecological account of the Suikerbosrand Nature Reserve. II. The phytosociology of the Ventersdorp geological system. Bothalia 13: 199–216.
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McAllister J. 1996. Master list of the birds recorded at Suikerbosrand Nature Reserve. Unpublished list. Nelspruit: Mpumalanga Parks Board.
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