SERPENTINESOF THE BARBERTON GREENSTONE BELT

Metal-rich rock outcrops and their associated vegetation.

by Gael J. Campbell-Young and Kevin Balkwill, University of the Witwatersrand

Berkheya coddii, a South African serpentine endemic with theability to accumulate nickel in its leaves and stem from toxic soil.Photo: K. Balkwill.

Dr Marla McIntosh, a botanistfrom the University ofMaryland, U.S.A., told a

colleague that she would beattending a conference onserpentine ecology. Her colleagueinquired as to why she was goingto a conference concerning snakes!Well, deceptive as thename may seem,serpentine ecology hasvery little to do withsnakes, but much to dowith a specific type ofrock that is rich in metals,and its associatedplantlife. The attractive,variegated shades ofgreen, sometimes withstreaks of red, of theserocks, as well as theirgreasy or soapy feel,resemble the skin of aserpent - hence the name.

What is serpentineecology?Serpentine ecology is arelatively new and notextensively explored fieldof study. Serpentine is'ultramafic' rock, rich inmetals such as nickel andchromium, and otherelements, e.g. magnesium.The resulting toxicity ofthe soil creates anenvironment that is notparticularly conducive toplant growth. Certainplant species are specifi­cally adapted to grow onserpentine, and someaccumulate the toxicelements in their leaves and stems.Numerous endemic species occuron serpentines all over the world,and the conservation of these sitesis of utmost importance. Animportant plant that is endemic toSouth African serpentines isBerkheya coddii, a useful indicatorof serpentine soil. 'Hyperaccumu-

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lating plants' are currentlyreceiving much attention, as theirability to accumulate heavy metalsmakes them useful for rehabili­tating mine dumps, where the soilis too toxic to support much life.These plants can also be harvested,in a process known as phyto-

mining, during which metals areextracted from the plants themselves.Where are serpentine areas inSouth Africa?Major serpentine outcrops occur intwo regions in South Africa,namely the Greenstone Belt of theBarberton mountains(Mpumalanga) and a band from

Potgietersrus to Duiwelskloof in theNorthern Province. Smalleroutcrops also occur on theWitwatersrand and in KwaZulu­Natal. Thirty-six serpentine siteshave been identified in theBarberton Greenstone Belt, ofwhich thirty have been mapped by

geologists. The remainingsix have been identifiedbecause of the presence ofthe nickel hyperaccumu­lating plants, Berkheyacoddii and B. rehmanniivar. rogersiana. The sitesoccur in an invertedequilateral trianglecentred on Barberton,with sides approximately100 km long, and showconsiderable variation inhabitat, soil chemistry andspecies richness anddiversity. The soils haveconcentrations of nickeland chromium highenough to be toxic toplants.

The Barberton GreenstoneBelt serpentinesApproximately 620serpentine-tolerant taxa(species level and below)of 298 genera and seventy­four plant families growon serpentine in theBarberton Greenstone Belt.The Asteraceae has themost representatives andits largest genera areSenecio, Helichrysum andBerklleya. The Asteraceaecontributes eleven

endemic species, the Acanthaceaeand Anacardiaceae, three each, theAsclepiadaceae, Lamiaceae andLobeliaceae, two each and theAdiantaceae, Celastraceae,Fabaceae, Iridaceae, Liliaceae,Proteaceae and Poaceae, one each.Eleven of the endemics arerestricted to single sites. Three

Veld &' Flora March 2000

endemic BerkJwya taxa and twoendemic Senecio taxa hyperaccu­mulate nickel, and Berkheya coddiihas become the subject of intensiveresearch because of its potentialvalue for re-vegetation and otherproperties.

At the Agnes Mine site about12 km south-west of Barbertonfourteen endemics were identified,one that is unique to the site andthree nickel hyperaccumulators.They include Aloe thorncroftii,Asystasia subbiflora, Berkheyacoddii and B. rehmannii var.rogersiana (both hyperaccumu­lators), Brachystelma dyeri, a newspecies of Cheilanthes, Cyplliaelata, Indigofera crebra, a newspecies of Ocimum, Ozoroabarbertonensis, a new species ofRhus, a new species of Sartidia, aSenecio hyperaccumulator that issimilar to S. coronatus, andGladiolus serpenticola. This site isrelatively undisturbed, and twovery small areas are conserved asthe Cythna Letty and HaroldThorncroft Nature Reserves, but themain part has no formal conser­vation status. The owner, SAPPI, isinterested in having it declared a

Veld &' Flora March 2000

National Heritage Site.At,Mundt's Concession, about

5 km'north~east of Barberton intrue low\l~ld vegetation, sixendemtcs, three unique taxa andone hyperaccumulator have beenidentified. Endemics include thehyperaccu,p:;mlator Berkheya nivea,a n~w speCies of Gymnosporia,Protea curvata which is restrictedto this site, a Rhus, Sclerochitontriacanthus and Gladiolusserpenticola.

Diepgezet serpentine, 25 kmsouth south-east of Barberton, isthe most intensively sampledportion of the larger Msauli Mineserpentine. Endemics includeBerkheya coddii, B. rehmanniivar. rogersiana, a species ofBrachystelma (close toB. franksiae), a new species ofOcimum and Salpinctiumhirsutum. The Msauli site is themost disturbed area because of theactivities of the asbestos mine, butthe mine is reaching the end of itsproductive life and will berehabilitated and closed. The site isowned by the Mpumalanga ParksBoard, but is excluded from theSongimvelo Game Reserve. It is

part of land that forms a link withMalolotja Nature Reserve inSwaziland.

The Dunbar Valley occurs withinSongimvelo Game Reserve and hasthe highest number of taxarecorded so far, with a total of 227identified, including the fourendemics Berkheya coddii, a newspecies of Helichrysum, anOcimum species and a new speciesof Sartidia. This is one of the leastdisturbed sites because of itslocation within the Game Reserve,although grazing by herbivores(such as zebra and rhino) and cattle(at one end of the site) takes place.

Groenvaly is the largestserpentine site in the GreenstoneBelt, situated near Badplaas in highaltitude grassland. Endemicsinclude a new species of Athrixia,Berkheya coddii, B. rehmannii var.rogersiana, a new species ofDicoma (which is similar toD. anomala), a new species ofInezia (similar to 1. speciosa) and anew species of Sartidia. TheAthrixia and Inezia werediscovered on a field trip withSarah Smith from Kew. On thewhole, this site is undisturbed,

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although part of it has been plantedwith pines. Most of this land isowned by SAPPI, who is interestedin declaring this site a NationalHeritage Site too.

Of the five sites, initially onlyDunbar Valley was formallyconserved. However, withMpumalanga Parks Board assumingresponsibility for, and consoli­dating much land into theBarberton Nature Reserve(including Mundt's Concession], amuch improved conservation statusfor serpentine in the BarbertonGreenstone Belt has been achieved.Despite this, the number ofendemics at Agnes Mine andGroenvaly make it urgent for us tocollaborate with SAPPI to havethese two sites declared NationalHeritage Sites, and thus guaranteetheir conservation.

Third International Conference onSerpentine EcologyThis conference was hosted byProf. Kevin Balkwill, an organizingcommittee of internationaldelegates and an action team fromthe c.E. Moss Herbarium, and took

place at Berg-en-Dal restcamp inthe Kruger National Park, in March1999. Countries representedincluded Australia, Belgium,Brazil, Canada, Cuba, England,France, Italy, Mozambique, theNetherlands, New Caledonia, NewZealand, Portugal, Scotland, SouthAfrica, Spain, Sri Lanka, Sweden,Turkey and the United States ofAmerica. Many aspects ofserpentine ecology were addressedat the conference, and appliedstudies led to stimulating discus­sions, including such issues asre-vegetation and phytomining.Delegates visited all the serpentinesites mentioned above, and ahighlight of the post-conferencetour was a visit to the beautifulDunbar Valley - a real Africanadventure as delegates were driventhere in four-wheel-drive vehicles,through thick bush and rivers.

The next conference (2003) islikely to be held in Cuba, whichboasts the world's richest source ofnickel hyperaccumulating plants.

The conference left researchersfeeling inspired about their workand encouraged to press on in their

struggle for the conservation ofserpentine areas. Priorities are togather as much information aspossible regarding serpentinesaround the globe and to presentsuch information to authoritiesable to ensure the survival ofserpentine sites. WI

AcknowlegementsThe Third International Conference onSerpentine Ecology was sponsored by theStella and Paul Loewenstein Charitableand Educational Trust, the Wits UniversityResearch Office, the Anglo Gold Fund, theAnglo American Chairman's FundEducational Trust, the National ResearchFoundation, the Nickel Producers'Environmental Research Association, theSouth African Journal of Science and theformer Botany Department at WitsUniversity (now the Department of Animal,Plant and Environmental Sciences).

About the authorsGael Campbell-Young is an M.Sc. graduatewho is currently working as a Researcherat the C.E. Moss Herbarium at WitsUniversity. Prof. Kevin Balkwill is theCurator of the c.E. Moss Herbarium at theDepartment of Animal, Plant andEnvironmental Sciences at Wits University,whose field of research includes southernAfrican serpentine ecology.

Conference delegates approaching Dunbar Valley on four-wheel-drive vehicles. Photo: G. J. Campbell-Young.

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