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Barberton / Makhonjwa Mountain Land (BML)

	Afrique du Sud (Afrique)
Date de soumission :	15/04/2008
Critères:	(viii)
Catégorie :	Naturel
Soumis par :	Ministry of Environmental Affairs and Tourism
Etat, province ou région :	Mpumalanga Province
Ref.:	5367

Description

The area in question is located largely within the Barberton Mountain Land (BML).  It is also known to geoscientists worldwide as the Barberton Greenstone Belt (BGB), composed of the rock sequences of the Barberton Supergroup.  Its varied and complex, folded rock-types give rise to deeply 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 steep and rocky, with moist grassy uplands and forested valleys.  The altitude ranges from 600 to more than 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 did 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 the region 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 NW Swaziland.  The region is mainly used for timber growing, nature conservation, catchment protection and communal livestock grazing.  Gold mining was the major economic activity and after 120 years some of the original mines are still producing.  New mines and different minerals, mostly outside the BML, are likely to maintain the important role of mining in the district. Timber growing, having reached saturation levels, is unlikely to expand. 

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 the discoveries 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.  

From these backgrounds, the twin brothers Richard and Morris Viljoen, while student geologists in 1969, first described distinctive Archaean lavas from the Komati river valley, now known as komatiites.  This landmark discovery identified the oldest volcanic rocks of a hitherto unknown (ultramafic) composition. It suggested their formation at temperatures approximating 1650ºC - the hottest ever described for volcanic rocks on the Earth's surface. Their scientific publications triggered new enquiries into the nature of the early Earth that are continuing to this day. Many subsequent discoveries contributed to our present understanding of the significance of these extremely ancient but remarkably well preserved rocks.  They include: the evolution of Earth's atmosphere; the origin of life; the growth mechanisms of continents; and the composition of the earliest oceans.   

Thus, while the area continues to yield gold to this day, the past half century has seen the BML's geology achieve a different type of fame, more significant and longer-lasting than its colourful gold-rush past.  Its importance is now derived from the extreme age of its rocks (ca. 3650 - 3100 million years), their excellent state of preservation, their low degree of geological disruption, and ease of access for scientists and laypeople alike. Rocks of similar age and even older, are known from a few other parts of the world (see Sect. 6). But not one combines the outstanding and diverse values of the BGB.  This region offers a virtual library of information at the limits of terrestrial time and allows us to study and learn about the origins and earliest history of our planet (C. Heubeck, in lit.). 

". . 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 precise extent of the potential World Heritage Site is not yet defined. Its outer limits lie within the South African portion of the BML (see Map 1). 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. This land use pattern, together with currently active mining, provides a guide as to which 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.  The oldest and most studied elements of the Archaean sequence are located in the Komati river valley to the south of the BML.  Including all key elements 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 participatory and detailed planning.

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

• Songimvelo Nature Reserve (State owned)   35800  ha
• Songimvelo Nature Reserve 'Panhandle' section (State owned)      13250  ha
•  Mountainlands Nature Reserve (Community, Public, Private Sector Partnership)   16700ha
• Barberton Municipal Nature Reserve (Municipal land)   350 ha
• Barberton Nature Reserve  (State owned)  2450 ha  
• Nkomazi Wilderness (Private)  30000 ha

Valeur universelle exceptionnelle

Justification de la Valeur Universelle Exceptionelle

Barberton Mountain Land contains the oldest well preserved sequence of volcanic and sedimentary rocks on Earth.  These highly accessible Archaean exposures present a continuous 350 million year sequence of rocks, from 3600 million years in age.  Their physical and chemical characteristics provide an unparalleled repository of scientific information about the early Earth.  The outstanding value of these rocks lies in the large number of sites and features that, when combined, provide 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, biomats and other organically derived material;  
• records of:

- the formation of the earliest continental crust;

- several of the earliest and largest meteorite impact events; 

- the chemical and physical nature of the Archaean ocean, including precise tidal intervals; 

- the composition of the early atmosphere; and 

- the nature of the environments within which the earliest life forms originated and developed;  

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

The outstanding value of these rocks is also due to their remarkable state of preservation.  They are not entirely unaltered, but enclaves exist where original components are intact for most rock types in this long Archaean sequence.  From these sites geologists and paleobiologists 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 features that readily attract a range of visitors, general tourists and special-interest groups.  There are high levels of biodiversity, especially plant endemism; unspoiled scenic, wilderness and watershed values; important cultural and historic features, including the site of South Africa's first real gold rush.  The site is also readily accessible and has comfortable year-round climate.   

These varied and attractive features, located close together, create strong potential for sustainable tourism, which in turn, leads to economic growth and poverty alleviation.  Tourism developments provide for easier and wider visitor access and the generation of revenue.  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.

Satements of authenticity and/or integrity

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 validated by the exhaustive and detailed peer-review system of technical geoscience publications.  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 publications, 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, also provides 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 ‘sufficient 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.

Comparison with other similar properties

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 emphasizing 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 (542 million years bp).  This time period, however, represents only the last 13% of the measurable age of rocks on Earth, the oldest being ca. 4100 million years old.  Wells (1996) collapses the remaining 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 or sites of broader geological significance in the distant 87% of Earth's history.  Whatever the reason, there are no inscripted World Heritage Sites in this final category.

The BML contains by far 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 largely unaltered by the passage of vast periods of time.  That is why the rocks still preserve microfossils and other clearly interpretable, detailed evidence of their origins (such as chemical composition, isotopes etc.).  That is why, in the unmatched 350 million year sequence of the Archaean eon that is represented by the rocks of the BGB, 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. 

In summary, there are no inscripted geo-heritage sites from the Precambrian on the World Heritage list.  Fossil sites of this age are presumably not expected or extremely rare, until the discoveries in the Barberton Greenstone Belt pushed the time-frontier of life back an incredible one billion years (Walsh and Lowe, 1985; Westall, 1998).  The two existing stratigraphic sites 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 (NW Territories) where 4 000 - 2 800 myr old 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. They are also difficult to access for a wider interested public.

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 Myr), 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 around 3 million years old, one of the richest hominid/pre-hominid sites known.  No meaningful comparison can otherwise be made with the extremely old, multidimensional, well-preserved and accessible Archaean features of the Barberton Mountain Land.