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The Barberton Mountain Land, Barberton Greenstone Belt or Makhonjwa Mountains

Date de soumission : 08/07/2009
Critères: (viii)
Catégorie : Naturel
Soumis par :
Barberton Mountain Land WHS Nomination Committee
Etat, province ou région :
Mpumalanga; covering part of at least two Municipalities: Umjindi Local Municipality (Barberton) and Albert Luthuli Local Municipality (Badplaas).
Ref.: 5456
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Description

The area in question is contained within what geologists refer to as the Barberton Mountain Land (BML), also known as the Barberton Greenstone Belt or more technically, the Barberton Supergroup geological formation. Its varied geology gives rise to steeply incised mountainous terrain that stretches from the Lochiel Plateau in the south to the Nelspruit-Komatipoort area in the north and straddles the Swaziland border. It includes part of the Komati river catchment in the south west, the de Kaap catchment in the north and Mahlambanyathi and Crocodile Rivers in the northeast. The hills are rocky, with moist grassy uplands and forested valleys. The altitude ranges from 600 to 1800 metres above mean sea level.

Historical summary

Oral history suggests that through the 1700s and 1800s the land was sparsely occupied by Swazi and other local pastoral people, together with their livestock. But the steep and rocky landscape does not provide well for human livelihoods and human occupation fluctuated both seasonally and according to the ebb and flow of local conflicts. Substantial settlements were rare, being limited mainly to the larger river valleys. 

At the time of European settlement in the 1860s it became a contested border zone.  Land deals were struck between the Swazi king and Transvaal colonists, the echoes of which remain to this day. The BML lies mostly in South Africa with about 20% in N-W Swaziland. The region is mainly used for timber growing, nature conservation, catchment protection and communal livestock grazing. Mining was a major activity but is now marginal and declining. 

The significance of the BML first became known to the world when alluvial gold was found at Kaapsehoop in 1875. This was followed by the Moodies and Barber's reef discoveries and a subsequent 'gold rush' into the hills above the Suid Kaap river.  Barberton's gold rush was quickly spent, soon to be dwarfed by finds on the Witwatersrand in 1886. South Africa's mineral wealth, at that time mainly from diamonds and gold, grew enormously. A direct by-product of this affluence was the development of geological science to support mining. In the first half of the 20th Century technical expertise and geological exploration expanded rapidly, supported by equivalent growth in academic research and teaching staff. 

From these ranks, the twin brothers Richard and Morris Viljoen, while student geologists in 1969, first described the distinctive Archaean lavas from the Komati river valley, now known as komatiites. This landmark discovery identified the oldest volcanic rocks (formed at temperatures approximating 1650ºC - the highest temperatures ever described for volcanic rocks on the Earth's surface) and triggered a fresh new enquiry into the nature of the early Earth. These discoveries, followed by many others, helped to publicise the existence of the ancient but remarkably well preserved Archaean sequences in the Barberton Supergroup. While the area continues to yield gold to this day, the last half century has seen BML's geology achieve a different type of fame, more significant than its colourful gold-rush past. This is derived from the extreme age of its rocks (3600 million years) the high quality of their state of preservation and the integrity and accessibility of such a significant 'Archaean time-slice' of the earliest history of the earth (3250 to 3600 million years).

". . the rocks in the Barberton belt provide a unique view of the early Earth that is quite literally unavailable anywhere else."                   Prof Don Lowe, Stanford University

Demarcation and land use 

The detailed extent of the potential World Heritage Site proposed, is not yet defined. Its outer limits lie within the South African portion of the BML (see Map 1 where it is referred to as the Barberton Supergroup). The ultimately delineated site can only be determined through a more detailed planning and negotiation process that will follow tentative listing. Map 2 gives a perspective of the biodiversity attributes of the area, highlighted by the Barberton Centre of Plant Endemism (BCPE) relative to conserved and transformed landscapes. The two dominant land uses in the area are nature conservation and timber production. These land use patterns, together with currently active mining, provide a guide as to what areas should be included for inscription. A sensible minimum area comprises the currently formalized nature reserves, on both state-owned and private land. 

It is acknowledged that several important geological "type localities" fall outside the protected area boundaries proposed. Including them within the protection status of the whole World Heritage Site is likely to be complex as it will be dependent on negotiation with landowners and communities. Their inclusion will be one of the objectives of the next phase of more substantial and participatory planning.

For the purpose of registering the BML site on the SAWHCC Tentative List, the properties will include:

Songimvelo Nature Reserve - State owned - 35 800ha

Songimvelo Nature Reserve 'Panhandle' section - State owned - 13 250ha 

Mountainlands Nature Reserve - Community, Public, Private Sector Partnership - 16 700ha

Barberton Municipal Nature Reserve - Municipal land - 350ha

Barberton Nature Reserve - State owned - 2 450ha

Nkomaz 200hai Wilderness - Private - 17650ha

TOTAL: 86 200ha

The half dozen 'Botanical Reserves', including some Natural Heritage Sites as well as other Protected Areas and specifically identified sites of significance, may or may not be included, dependant on the future WHS planning process.

Justification de la Valeur Universelle Exceptionelle

The features of the site that have Outstanding Universal Value (OUV) are primarily geological. Specific sites illustrating key scientific findings and events are listed at the end of this section.

In summary, the area contains the oldest well preserved sequence of volcanic and sedimentary rocks on Earth. These highly accessible exposures of Archaean rocks have characteristics that provide an unparalleled repository of scientific information about the early Earth. The high significance of the BML lies not so much in any one feature but in the large number of characteristics that, when combined, make the BML a unique and as yet only partially explored scientific resource.

Specifically the BML Archaean sequence includes: 

- records of Earth's earliest life forms, including microfossils, stromatolites and other organically derived material;

- records of: the earliest continental crust formations; several of the earliest and largest impact events; the nature of the Archaean ocean including precise tidal intervals; the nature of the early atmosphere and climate; and the nature of the surface environments within which the earliest life forms lived;

- the 'type-locality' of the distinctive komatiite volcanic rocks.

The exceptional scientific value of these ancient rocks is due to their remarkable state of preservation. They are not entirely unaltered, but for most rock types in this 350 million year sequence, there are enclaves where original components are intact. From these sites scientists have learned more about the Earth's early history than from any other comparable geological site. 

From a non-geological perspective the site has additional values that supplement and boost its outstanding values. These include scientific and aesthetic values that readily attract a range of visitors, general tourists and special interest groups.  There are high levels of biodiversity, especially plant endemism; great scenery, wilderness and watershed values; important cultural and historic features, including the site of South Africa's first real gold rush. Add to these, the site's accessibility and comfortable climate and you have a winning package. 

These varied and attractive features, located close together, create a huge potential for sustainable tourism and in turn, economic growth and poverty alleviation. Tourism developments provide for easier and wider visitor access. In turn, this improves access for scientific study, investment in protection, management and interpretative services and finally, a much broader reach for visitors to learn about and understand the world they live in, in an exciting natural environment.

The whole Archaean sequence of the Barberton Supergroup ranges in age from 3600 to 3250 million years before present.  These rocks occur in unmatched and highly accessible exposures, representing a 350 million year slice of Archaean time that is truly unique. One of the most outstanding features of these exposures so far discovered is that they have revealed by far the oldest microfossils ever described (3500 million years). In the late 1960s many eminent micropalaeontological researchers from the USA, UK and Germany, many associated with NASA, were conducted on collecting expeditions around Barberton Mountain Land. Their interest was to study Archaean organic material to compare with material brought back from the Lunar expeditions.

In keeping with the area's exceptional geology there is a correspondingly rich biodiversity. The steeply broken terrain, unusually mineralised soils (e.g. serpentine soils) high rainfall and extremes of temperature have given rise to a local Centre of Plant Endemism (Van Wyk and Smith, 2002), one of twenty such biodiversity hotspots in South Africa. Although this feature, on its own, does not rate OUV, when added to the geological values and outstanding wilderness and aesthetic qualities, it makes for a tourism attraction that geology, on its own, cannot provide. These supplementary values, along with the accessibility of the site, will attract researchers and tourists that will enhance the spread of knowledge and understanding of the early Earth.  These unique geological features have, since the late 1960s, attracted scores of international scientists annually, many returning every year to pursue long-term projects in various fields of cutting-edge research.   

Incidental to, and adding value to these main scientific features, are aspects of cultural significance that enrich overall visitor interest. These include:

- The oldest record of ancient mining located in NW Swaziland. Lion Cavern at the Ngwenya Iron Ore Mine (Bomvu Ridge) was initially dated at 41 250 BC - some seven times older than the oldest known flint mines of Western Europe. Later C14 dating of the Bomvu ridge material suggests a more likely age to be 70 000-80 000 BC!

- A rich contemporary history of dynamic local African cultures, colonisation and early gold mining;

- An extremely high frequency of stone-age tools and related artifacts as well as San cave paintings.

Qualitative statements by eminent scientists:

"The oldest well preserved sedimentary and volcanic rocks on Earth. ... These rock layers are like the pages of a book that we can read and translate in terms of early Earth's history.  Here in Barberton is the Rosetta Stone for this period of time."   Prof Don Lowe, Stanford University

"The rocks of the Barberton region represent the best-preserved example of the Earth's ancient oceanic and continental crust."   Profs Terence McCarthy and Bruce Rubidge, University of  the Witwatersrand

"Rocks from these areas provide the only direct information from which the earliest history of our planet can be reconstructed with confidence ... Because the world's oldest fossils have been found here, the area is a Mecca for scientists interested in how the young Earth worked 3 500 000 millennia BC, and in searching for new clues to the origin of life."   Prof Maarten De Wit, University of Cape Town

"The Barberton Mountain Land ... has come to be recognized in the world of earth science as one of the truly remarkable localities for understanding the history and evolution of the Earth .... These rocks provide scientists with a unique opportunity to study events that took place very far back in Earth's history. There are only a few places in the world where rocks of this great age are preserved, but few can match the diversity and spectacular exposures that occur in the Barberton Mountain Land".   Prof Carl Anhaeusser, University of  the Witwatersrand 

"On another continent, in another region where men have toiled and died for gold, the Barberton Mountain Land of the eastern Transvaal and Swaziland has become a mini-classic and a mecca for students of granite-greenstone terrains"   Prof  Preston Cloud (1988), Univ. California at Santa Barbara,

The most important specific geological sites could include: (Note: all the categories listed below can be found at more than one locality) 

-The type locality for komatiite volcanic rocks containing supercooling textures known as spinifex, and indicating high surface temperature eruptions. (several)

- Pillow-structured komatiitic basaltic lava

- The Middle Marker sedimentary layer separating dominantly komatiitic volcanic rocks from dominantly basaltic and felsic volcanic rocks.

- Banded chert formations with microfossils and other accumulated organic matter providing a potentially diverse record of earliest life (several)

- Ancient spherule beds from the earliest recorded impact events (at least four; each of which was far larger than the famous K-T impact event which led to the extinction of the dinosaurs)

- Ancient hot springs in the Fig Tree Group that provided an environment for bacteria and early life forms (several, significance contended)

- Sedimentary cross-bedding in ancient sea-floors allowing precise tidal and lunar measurements

- Various Archaean conglomerates that allow insight into time sequencing

- Oldest well preserved layered ultramafic complexes containing chrysotile asbestos and magnesite deposits

- Gold mineralization, including historic mining sites

- Granitic rocks of various types, which represent major crust-forming events

Criterion (viii):  The representative area contains the oldest well preserved sequence of volcanic and sedimentary rocks on Earth. These highly accessible exposures of Archaean rocks have characteristics that provide an un parallel repository of scientific information about the early Earth. The high significance of the BML lies not so much in any one feature but in the large number of the characteristics that, when combined, makes the BML and as yet only partially explored scientific resource.  

Specifically the BML Achaean sequence includes:

- records of earths's earliest life forms, including microfossils, stomatolites and other organically derived material;

- records of: the earliest continental crust formation; several of the earliest and largest impact events; the nature of the archaeon ocean including precise tidal intervals; the nature of the early atmosphere and climate; and the nature of the surface environments within which the earliest life forms lived; the type-locality of the distinctive komatiite volcanic rock.

The exceptional scientific value of these ancient rocks is due to their remarkable state of preservation. They are not entirely unaltered, but for most rock types in this 350 million years sequence, there are enclaves where original components are intact. From these sites scientists have learned more about the earth's history than from any other comparable geological site.

Déclarations d’authenticité et/ou d’intégrité

Authenticity in terms of the WHC is not a major issue in respect of Natural Heritage sites (WHC Operational Guidelines, Sect II E, 2005) as it is catered for by the peer-review system of scientific publication. The published record of scientific research in the BML is very extensive, numbering more than 2330 geological publications alone since 1875 (C. R. Anhaeusser, five bibliographies from 1976-2002). These include peer-reviewed papers, survey reports, research theses, maps and text books. The experience and seniority of the geologists quoted above, most of who are active researchers in the region, provides the most credible assurance.

The integrity of the site requires consideration of a sufficient and manageable area with practical and effective boundaries. In addition, paragraph 93 of the Guidelines states:

"...(a site) should contain all or most of the key interrelated and interdependent elements in their natural relationships."  

The issues involved in deciding on the size of the site, concern: ownership; access; controlling development; and providing for and managing resources and visitors. At this site in Mpumalanga, it extends further, and involves Integrated Development Planning, part of a mandatory state responsibility at the Local Government level. The larger the area and, in particular, the larger the number of land owners and land uses involved, the greater the complexity and cost of management. Management planning will also have to deal with the concept of geo-site conservation and geo-tourism which are relatively new in South Africa.  

The 'suffiIcient area' referred to above must allow not only for currently known sites but should include localities where future research opportunities lie. This requires the existing geological 'type-localities' and known sites to be included plus, a sufficient sample of the rest of the 'Archaean time-slice' to protect the resource base for future research. Who knows which sedimentary layer in that Archaean sequence will reveal the next "gee whizz" discovery. Improving technology will undoubtedly test our current interpretations and theories in such an extreme area of research.

Political and Planning Support : Local support for WHS listing is premised on a rising consensus that development is urgently needed in the region and that tourism-related development is the most sustainable option. The Premier of Mpumalanga is personally aware of and supportive of the project and has had it presented to the Provincial Cabinet in July 2007. It forms part of the Premier's "Heritage, Greening Mpumalanga and Tourism Flagship Project" for which funds have already been allocated.  At Local Government level the Mayor of Umjindi Local Municipality (Barberton) has been proactive in aligning civil society support for Barberton as an "Eco-Heritage Town". This pre-determines a future development scenario based on growing outdoor tourism which, in turn, is based on the unique natural attributes of the area. The Municipal Council contributes to a Public-Private-Partnership in tourism promotion, in the form of Barberton Community Tourism (BCT), a non-profit (Section 21) Company, dedicated to promoting sustainable tourism in the region. BCT is an active supporter and contributor to the WHS listing process, at present facilitating a grant from the National Heritage Council to help compile this proposal.

Much regional planning has taken place over the last eight years. Most of it advances regional development through growing a tourism based economy dependent on conserved and accessible natural resources. Among the many studies conducted, the following planning reports demonstrate both the integrated approach and the consensus and support that exists (also see reference list). 

- Maputo Development Corridor, Multi-agency Tourism Impact Study, 1998.

- Tourism and Biodiversity Corridor Study and Development Plan. DEAT/MPB report, 2001

- Badplaas/Barberton/Malelane focus-area study on Tourism Development, JICA/DEAT Report, 2002.

- Barberton-Complex Strategic Eco-Tourism Development Plan, MPB/ICS Report 2002.

- Songimvelo/Malolotja Trans Frontier Conservation Area, Tri-National MOU. October 1999, and its implementation agreement signed in 2006.

At present the site is not formally recognized by National or Local Heritage Institutions, although the process is under way. This lack of prior recognition is partly due to South Africa not having a public programme to conserve geological heritage per se. Efforts by geological interest groups are underway to establish such a system. The process of applying for global recognition for the country's prime sites will materially assist in this endeavour. (We are aware that the prior recognition issue drew criticism of the process used to register the Vredefort Impact Structure.) A parallel process is in motion to attain National Heritage Site recognition for the BML, which will likely be conferred prior to the final WHS submission.

Comparaison avec d’autres biens similaires

One of the first attempts to systematically organize geo-heritage sites for conservation purposes was commissioned by IUCN in 1996. Wells (1996) proposed a classification system based on geological age and emphasising the value of the fossil record, and tabulated the allocation of sites per category.  His age-classes follow the established geological/palaeontological time scale of 'epochs' and 'periods' but they stop at the Cambrian (545 m/ybp).  This time slice represents only the last 13% of the measurable age of rocks on Earth, the oldest being 4 100 m/ybp. Wells (1996) collapses the outstanding 3.5 billion years into a single 'Precambrian' period. It appears that conventional wisdom, or the limits of technology at the time, did not anticipate Precambrian fossils. Whatever the reason there are no inscripted World Heritage Sites in this final category.

Dingwall et al (2005) present the following definitions to assist the value judgements required by comparative analysis (edited for brevity): "Outstanding: the World Heritage Convention sets out to define the geography of the superlative - the most outstanding natural and cultural places on Earth; "Universal: The scope and significance are global ... importance is to all people of the world ... WH properties cannot be valued from a national or regional perspective; "Value: What makes a property outstanding and universal is its "value". Value is established by clearly defining its worth; assessing its quality; and ranking its importance based on clear and consistent standards."

This means that World Heritage selection has to be: The very best sites, accessible and important to all people, possessing the highest existing and potential scientific value.

The BML contains the oldest geology ever proposed for WHS inscription, but that is not its main value. The reason for its high value lies in the state of preservation of the rocks that allows scientists, with increasingly sophisticated technology to interpret the earliest history of the earth. This is because the chemical and physical structure of these rocks, have miraculously remained unaltered by the passage of vast periods of time. That is why the rocks preserved microfossils and other clearly interpretable evidence of their origins. That is why, in the unmatched 350 million year sequence of the Archaean eon that exists in the BML, the future discoveries from these geological exposures are likely to be even more enlightening and valuable.

All the inscripted World Heritage sites that have "earth science features of outstanding universal value" (184 of them) may be provisionally sorted into 13 Themes (Dingwall et al, 2005).  If BML is distinguished primarily by features that fit Themes 4 and 5, with support values from Theme 13, then comparisons should be made mainly with sites claiming these attributes. In addition there are a further 60+ sites, inscripted for other Natural Heritage values, such as biodiversity. Most of these sites have "earth science values" supporting the primary features for which they earned inscription.  Comments summarising these comparisons are set out below.

Stratigraphy (Theme 4): (from the 184 sites with "earth science features"): Two sites have features of OUV. Neither present other features of significant value. 1 - Grand Canyon (USA, Permian period); 2. Dorset & East Devon Coast (UK, Mezozoic era) which is mainly an exemplary fossil site.

Fossils (Theme 5): (from the 184 sites with "earth science features"): Eleven sites have OUV (+ one [Ngorongoro, (TZ, Pleistocene)] with a "possible" OUV feature).  None presents other features of significant value. Of the 11 sites, only three are from the Devonian era or older, and all are from Canada (in increasing age): Miquasha, Devonian (fishes and forests); Gros Morne, Ordovician (fishes and corals) and Burgess Shale from the Cambrian (first trilobites).

Meteorite Impacts (Theme 13): Only the Vredefort Impact Structure is inscripted, presenting no other features of significant value.

There are no sites that have Stratigraphic, Fossil or Meteorite Impact features, from any of the other World Heritage sites inscripted for other natural heritage values. (Extracted from Dingwall et al (2005)

In summary, there are no inscripted geo-heritage sites from the Precambrian, anywhere on the World Heritage list. Fossil sites of this age are presumably not expected or extremely rare, until the discoveries in Barberton's komatiites pushed the time-frontier of life back an incredible one billion years. The existing stratigraphic sites (2) are both relatively young in geological terms.

A thorough comparison should include a sample of known sites that have not been brought to the notice of the WHC, examples:

Pilbara, in northern West Australia, is the most comparable site but is not registered as any form of heritage asset. It is more extensive than the BML site, more remote and much more difficult to access. Material is very poorly exposed, deeply weathered and includes a much lower diversity and smaller age-range of available rocks (D. R. Lowe, in lit.).

There are Canadian sites in the Slave Province (N-W Territories) where 4 000-2 800 Myr rocks are reported, and along the Labrador Coastal Strip (opposite West Greenland). There are also sites in West Greenland, in the Fiskenaesset and Nuuk regions, where the Amitsoq gneisses are located as part of the North Atlantic Craton.  These exposures have an age range of 3870-3380 Myrs. The Isua greenstone belt is the oldest known greenstone belt in  

the world, but is strongly metamorphosed, fragmented and poorly exposed, being partly covered by the Greenland ice sheet. (C.R. Anhaeusser, in lit.). As such these sites have far less potential to yield important new information about the Earth's early surface and life than the BML.

These sites are all older than, or have a similar age to, the BML but are highly fragmented and metamorphosed and do not provide a clear record of events in the early stages of Earth's history (McCarthy and Rubidge, 2005). There are snippets of rocks of this age in many other areas, but the continuity of the BML record is unrivalled. Also, in many of these areas, such rocks are covered by deep soils, forests, or younger materials. (D. R.  Lowe, in lit.). 

It is also necessary to look at the range of WHS inscriptions within South Africa to consider the balance provided by other candidate sites, and those that have already been inscripted. Only two of the SA sites have any geological features of value.  These are the Vredefort Impact Structure and the Cradle of Humankind. The first is truly ancient (~2023 Myrs), but is otherwise one-dimensional as the stand-alone oldest and largest known meteorite impact site. The second is very recent, comprising karst breccia deposits of around 3 million years old, one of the richest hominid/pre-hominid sites known. No meaningful comparison can otherwise be made with the Archaean features of the Barberton Mountain Land.