SEKHUKHUNELANDFLORISTIC WEALTH VERSUS PLATINUM AND CHROMIUM RICHES.

by Stefan Siebert and Braum van Wyk, H.G. W]. Schweickerdt Herbarium, University of Pretoria

of the Steelpoort and OlifantsRivers have eroded deep, broadvalleys to the west of the north­eastern Drakensberg Escarpment.These valleys are traversed by

the Leolo Mountains and manysequences of undulating hillsthat are mostly orientatednorth-south (but sequenceswith an east-west orientationoccur south of theStrydpoort Mountains).

As a result of the low goldprice and the rise in theplatinum and chromiumprices, Sekhukhuneland isexperiencing rapid devel­opment, at a pace unprece­dented for this region.Mines are shooting up likemushrooms. This is ofgreat benefit to the localpeople, most of whom arepoor and unemployed, but

has a detrimental effect on the rich natural flora.Earlier unsuccessful mining activities, without any

attempt at rehabilitation, resulted in extensive damageto the immediate environment, which is visible asscars on many of the hills and mountains of theregion. Open casts and mine dumps must be rehabili­tated under new laws, but it is the indirect effect ofthe mining industry that causes the biggest problems.With the mines comes a tremendous influx of peopleto an area already densely populated.

The Sekhukhuneland centre of plant endemism in South Africa.Map: F. du Plessis.

Undulating norite and pyroxenitehills characterize theSekhukhuneland

landscape. The rock that makesup these hills was formedduring a magnificent event.A series of surges led tothe emplacement ofmagma on the surface asa result of alternatingstress and pressureconditions in the earth's crust.Lava was forced into the interiorof the southern African subcon­tinent, with the lava flowcontinuously fed from acentral volcanic pipe. Thelava crystallized and gave riseto different layers, which ---have been classified asthe Bushveld Complex.Today these rocks coveran area of about66 000 km

2, the largest

layered intrusion in the world. The RustenburgLayered Suite is the outermost of these layers, with theeastern Rustenburg Layered Suite (Sekhukhunelandregion) holding some of the highest concentrations ofheavy metals such as chromium, platinum, titaniumand vanadium in the world. These high concentrationsof heavy metals are contained in the rocks and soils ofthe region.

Sekhukhuneland is a lowveld enclave surroundedby highveld and middleveld. Millions of years oferosion by the drainage systems

Sekhukhuneland is scarred by surface mining which is the mosteconomical method used to extract and remove norite,chromium, vanadium and platinum.Photo: A.Eo van Wyk.

RightThe Leolo Mountainsis the largest featurein Sekhukhuneland.Spectacular rockformations can befound on the summit.Below rightClumps of afro­montane forests occuron the summit of theLeolo Mountains.BelowThe economic richesof Sekhukhunelandlie in its rocks, as canbe seen at theDwarsrivierMonument where theblack chromiumbands in theanorthosite rock hasbeen exposed by theDwars River.Photos: A.E. van Wyk.

Sekhukhuneland has been the home of the Pedi, a strongly culturalpeople, who use to live in harmony with their environment. They havebeen using their natural resources sustainably for hundreds of years.Foreigners who have moved and settled in Sekhukhuneland in search ofjob opportunities usually do not have the same cultural respect for theirnew environment. This is already evident in many parts ofSekhukhuneland, where large specimens of traditionally protected treessuch as Boscia foetida, Schotia brachypetala, Catha transvaalensis andAcacia burkei have been chopped down in recent years. Historically,these trees were selectively left in fields and settlements for cultural,medicinal and shade purposes.

Other threats to the vegetation are the result of urban developmentand its associated activities, for example towers and reservoirs on hills,water pipelines, roads, housing developments, alien plants, over­utilization of wood, overgrazing, intensive collection for muti marketsand pollution by smelting industries. •

Veld &' Flora December 2001

ClimateSituated along thenorth-eastern DrakensbergEscarpment, one mayexpect Sekhukhunelandto have a cool, moistclimate. However, this isonly true for the grass­lands in the extremesouthern parts of theregion, which borders theSteenkampsberg, and forthe higher plateaux of theLeolo Mountains, wherethe annual rainfallaverages approximately700 mm, with a meantemperature of 19 ce.The larger part of Sekhu­khuneland is a semi-aridsavanna that lies in therain shadow of theEscarpment which has anaverage annual rainfall of400 mm and a meantemperature of 22 ce.

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Above Catha transvaalensis (Sekhukhune bushman's tea) is acharacteristic tree of Sekhukhuneland and can be found on rockyhillsides of pyroxenite, norile, magnetite and dolomite.Below Thaba Sekhukhune forms the western boundary of theSekhukhuneland floristic region. ote the autumn colours ofKirkia wilmsii in the foreground. Photos: A.E. van Wyk.

Flora and vegetationSekhukhuneland is underlain by ultramafic rock (richin metals like nickel and other elements likemagnesium), a substrate treated as serpentine bybotanists. The vegetation of Sekhukhuneland, like thetrue serpentine flora of the Barberton Sequence, ispredominantly of Zambezian floristic extraction.Three major vegetation and floristic regions convergein Sekhukhuneland, namely bushveld (savanna),grassland and elements of afromontane forest. Thishas resulted in a transition zone with a diverse flora.The more temperate areas of Sekhukhuneland arecharacterized by sparsely wooded grassland andafromontane bush clumps. Relict forest patches arefound on the summit of the Leola Mountains. Thehigh-altitude southern and central regions ofSekhukhuneland are characterized by grasslands,which are an extension of those on theSteenkampsberg. Bushveld is dominant in all thewarm dry valleys, plains and low-altitude mountainslopes and hills. The open plains are usually charac­terized by bushveld vegetation interspersed withnumerous karroid elements.

The diversity of the plant species in Sekhukhune­land is striking. Even more remarkable are the floristicchanges that can be observed over short distances -a phenomenon usually associated with the CapeFloristic Kingdom. The marked changes in altitude(1500 to 700 m) over short changes, diverse geology(shales, quartzites and sandstone to norite, pyroxeniteand anorthosite), changing topography (level toundulating), varying regional climate (cool, wet towarm, dry) and complex climatic history (grassland,bushveld, forest and karroid vegetation), probably allcontributed in one way or another to the present-daydiversity of the Sekhukhuneland flora.

The seclusion of the 'basin' by the high ground

Above Fourteen succulent Euphorbia species occur in Sekhukhuneland, of which theendemic Euphorbia sekhukhuniensis (get/one in the Pedi vernacular) occurs the mostfrequently.Below Jamesbrittenia macrantha is a spectacular endemic wildflower in Sekhukhunelandwhich is especially common in disturbed road reserves. Photos: A.E. van Wyk.

frequently occurring trees/shrubs are Acacia cajfra,Cussonia transvaalensis, Euclea crispa, Rhus leptod­ictya and Vitex obovata subsp. wilmsii. The alieninvasive tree Acacia dealbata is a major problem inthese grasslands. Wetlands and rivers in the regionalso have their own set of associated trees of whichSalix mucronata is probably the most obvious. Otherwoody species include Acacia karroo. Nuxia gracilisand Rhamnus prinoides.

Species of special concernAll these different tree associations occur over shortdistances and all of them can be found within akilometre radius in the central part of Sekhukhune­land. The various plant communities are interspersedand no two communities have the same speciescomposition as a result of the diverse habitat and thespecific preference of the different taxa concerned.

encompassing it, together withthe heavy-metal rich andrelatively toxic soils, may haveserved as stimulus for the diversi­fication of plant lifein this 8 000 km

2area.

Approximately fifty endemicplant species, several of whichare still in the process of beingformally described and named,and several rare and threatenedspecies occur here.

The diversity of the flora iswell illustrated by the distrib­ution of trees in the region.Broad, arid valleys that traverseSekhukhuneland are charac­terized by thornveld dominatedby Acacia grandicornuta,A. mellifera and A. tortilis. Otherprominent trees include Albiziaanthelmintica and Dichrostachyscinerea. Trees typical of thesearid habitats are Boscia foetidasubsp. rehmanniana, Cadabatermitaria, Commiphora pyracan­thoides and Sesamothamnuslugardii. The sequences of drymountain slopes and hills inSekhukhuneland are dominatedby Combretum apiculatum,Commiphora mallis, Grewiaflava, Kirkia wilmsii andSterculia rogersii, with foothillscharacterized by Acacia senegalvar. leiorhachis, A. nigrescens,A. nilotica, Boscia albitrunca andTerminalia prunioides. Patches oferoded, heavy-metal soils occurthroughout the study area andare recognizable by a range ofsmall trees/shrubs, notablyBrachylaena ilicifolia,Bolusanthus speciosus, Euclealinearis, Euclea sp. nova, Ozoroasphaerocarpa and Rhus keetii.Other prominent and abundantwoody species of thesevegetation anomalies includeCombretum hereroense, Grewiavernicosa, Rhigozum obovatum,Tinnea rhodesiana and Vitex obovata subsp. wilmsii.On the southern aspects and higher altitudes ofmountains and hills there are stands of woodland withafromontane elements such as Apodytes dimidiata,Andrachne ovalis, Gymnosporia mossambicencis, Ilexmitis, Kiggelaria africana, Maytenus undata andPrunus ajricana. Rocky outcrops are common andwidespread throughout the region. Common treespecies on these outcrops include Catha trans­vaalensis, Combretum molle, Halleria lucida, Oleacapensis and Vangueria infausta. Other prominentspecies are Acacia ataxacantha, Aloe castanea,Commiphora marlothii, Euphorbia sekhukhuniensis,Hippobromus pauciflorus and Rhoicissus tridentata.

Although the grasslands in the south are very poorin trees, they are characterized by Protea cajfra andthe woody Elephantorrhiza elephantina, a newspecies of Rhoicissus and Rhus wilmsii. Other less

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Many endemic woody species areassociated with these differenthabitats such as the trees/shrubsCatha transvaalensis,Elephantorrhiza praetermissa andRhus batophylla, as well as thelarge succulents Euphorbiabarnardii and E. sekukuniensis.Also endemic to the region are theshrubby Asparagus sekhukhu­niensis and Rhoicissus sekhukhu­niensis, the yellow floweringgeophyte Zantedeschia jucundaand cryptic cream-floweredgeophyte Stylochiton sp. nova,the succulent Plectranthus vented,the spectacular purple-floweredJamesbrittenia macrantha and thered-flowered Hibiscus barnardii.

Most of these species areconsidered rare and endangered

the success, if any, of these opera­tions will only be apparent in thelong term.

In addition to the wealth ofendemics, twenty-six of the 1 800species that occur in Sekhukhune­land have provisionally met thenew IUCN criteria as part of theassessments made during theSouthern African Plant Red DataList Project. On a national level,three were assessed as 'criticallyendangered', namely Nemesiazimbabwensis, Stylochiton sp.nova and Tulbaghia sp. nova(probably a new genus), three as'endangered', namely Aneilemalongirrhizum, Raphionacmechimanimaniana andZantedeschia pentlandii, and afurther twenty as 'vulnerable'.

Jamesbrittenia macrantha,Orthosiphon !ruticosus,Phyllanthus sp. nova and Polygalasp. nova. Other interesting plantspecies that share this specializedhabitat with the endemics are fromarid regions in the NorthernProvince, Northern Cape andNorth West Province and includeGnidia polycephala,Jamesbrittenia atropurpurea,Nuxia gracilis, Plinthusrehmannii, Pterothrix spinescens,Phyllanthus parvulus var.garipensis, Rhigozum obovatum,Rhus keetii, Sesamothamnuslugardii and Stipagrostishirtigluma subsp. patula. Very fewalien plants occur in these dongas,an indication that this habitat typeis a natural feature of the region.

Left Zantedeschia pentlandii is near-endemic to Sekhukhuneland and endemic to the mountainous areas of the Roossenekal­Dullstroom region. Right The unfamiliar Hibiscus barnardii is an endemic of the undulating hills of Sekhukhuneland.Photos: A.E. van Wyk.

because of the impending develop­ment in the area. These taxa arecurrently known only fromspecific localities inSekhukhuneland, most of whichare in close proximity to themining and residential devel­opment in the region. Many otherplant species endemic to thenorthern provinces of SouthAfrica, and particularly near­endemics shared between thenorth-eastern DrakensbergEscarpment and Sekhukhuneland,are under the same threat.Organized plant rescue operationsat proposed development siteshave led to the re-Iocation of largenumbers of these taxa (notablysucculents) to various botanicalgardens in South Africa. However

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Other plant species of particularconcern are the taxa restricted tothe vegetation anomalies in theregion. These species are eitherendemic to Sekhukhuneland or areabundant in other arid regionshundreds of kilometres away.These vegetation anomalies areusually naturally eroded systemsand were first reported in the liter­ature and studied around 1950.Owing to the general attitudetowards erosion, these naturaldongas are used as dumping sitesby industries in the region.However, extensive field work hasshown that these areas areinhabited by a unique flora thatinclude endemics such as Cathatransvaalensis, Rhus batophyllaand R. sekhukhuniensis and

ConservationCurrently there is one conser­vation area in the northern regionof Sekhukhuneland, near the townof Mecklenburg. Potlake is a2 800 ha nature reserve ofmountain bushveld between theOlifants River and the Burgersfort­Pietersburg road. Althoughprolonged settlement in the pasthas left its mark on parts of thePotlake Nature Reserve, itsmountain and foothills of serpen­tinized harzburgite harbour a widevariety of plant species, includinga few undescribed ones. However,many more conservation areas areneeded to protect the diversehabitats of the region. In aneconomically productive devel­opment zone this is seldom

Veld fr Flora December 2001

Right Yellow arums flower profuselyand contribute to a mosaic of green,brown and yellow which covers thehillsides in December. Zantedeschiajucunda with its white-speckled leaves,is endemic to Sekhukhuneland.Photo: A.E. van Wyk.

possible without compromise.The most positive scenario at

present is the fact that miningcompanies are at least trying torehabilitate disturbed sites.However, what has been lost cannever be regained. What is reallyneeded is a comprehensive devel­opment plan for the whole region.Environmental Impact Assessmentconsultants and conservationauthorities alike have recom­mended it, but no real action planhas been developed. Uncontrolledmining, agricultural andresidential development of thearea will result in the irreplaceableloss of Sekhukhuneland's uniqueplant species and habitat. As asignatory to the Convention onBiological Diversity and as acountry that has geared itself forecotourism, South Africa shouldtake note of its dwindling naturalareas and the lack of conservationmeasures to sustainably protect itsbiodiversity. WI

Further reading:Cawthorn, R.G. 1999. The platinum and

palladium resources of the BushveldComplex. South African Journal ofScience 95, 481-489.

Crookes, D., Ireland, c., De Wit,M., Geach, B., Kgame, W. & Netshiluvhi,T. 2000. Benefits and costs of naturalresource use in Sekhukhuneland,Northern Province: Case studv evidencefrom Managaneng and Makwi'.Unpublished Report o. ENV-P-I-2000­013. CSIR, Pretoria.

Joubert, H. & Dreyer, A. 2000. Rocky roadfor rare endemics: Granite miningthreatens a rich Mpumalanga environ­ment. African Wildlife 54,18-19.

Siebert, S.J. 1998. Ultramafic substratesand floristic patterns in Sekhukhune­land. South Africa. M.Sc. thesis,U.?Jversity of Pretoria.

About the authorsStefan Siebert is currently the RegionalCoordinator of the SABONET (SouthernAfrican Botanical Diversity Network)Project and is stationed at the NationalHerbarium, ational Botanical Institute,Pretoria. To find out more aboutSABONET, visit the websitewww.sabonet.org.

Braam van Wyk is a Professor inBotany at the University of Pretoria andis the curator of the H.G.W.J.Schweickerdt Herbarium, Department ofBotany, University of Pretoria.

Veld &- Flora December 2001