Barberton mountains a haven for plants

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Thorncroftia lotterii TJ Edwards

Like an exclusive ark, the mountains around Barberton shelter a set of plant species that have evolved and adapted to this unique area for thousands of years. Although vast tracks of land here have already been changed by the actions of people, unlike many other ecosystems in the world, humans are doing their part to protect it.

More than twelve nature reserves conserve the threatened and significant plant species growing there and several of these have been established for the sole purpose of conserving just one or two species. All these reserves fall within the globally recognised Barberton Centre of Floristic Endemism and the Barberton Greenstone belt, a mountainous geological landscape that tells the story of the dramatic beginnings of earth.

The geology of the area dates back 3,6 billion years and due to its remarkable preservation is studied by earth scientists from across the globe who flock there every winter. This early landscape was beneath the sea for millions of years and contains evidence of some of the first life forms to have evolved, intertidal zones as well as ancient beaches. Through time, it has been twisted, buckled and tilted giving rise to the gentler, more curvaceous mountain scenery of today.

Outcrops of serpentinite occur throughout the Barberton Greenstone belt. Serpentine loosely refers to a broad group of minerals associated with the weathering of high iron, calcium and magnesium rich rocks.  These rocks give rise to soils which are less fertile than more widespread soils and having high concentrations of heavy metals which are potentially toxic to plants. At least 30 plant species within the Barberton Centre have evolved on these soils and are now totally adapted to life on the serpentine soils. That may not sound like a lot, but there is worldwide interest in plants growing in serpentine soils because of their usefulness in testing ecological and evolutionary scenarios and because serpentine outcrops are known to harbour high rates of plant endemism.

The geology in the Barberton Centre, which includes the adjacent north western parts of Swaziland, underlies a rich diversity of 2176 plant species discovered to date with some 80 species having been identified as endemic, which means these are rare as they are confined to a particular narrow location or habitat type. After the Cape fynbos, the natural grassland biome is home to the highest amount of plant species in the country. Although grasses dominate in numbers, it is the non-grassy herbs that make up the bulk of the species and endemics. Proteas, bulbs, aloes and other succulents count among the special endemic treasures there.

Most of the Barberton Centre’s endemics are restricted to the high lying grassland areas or the serpentine soils. It is currently believed that for an endemic species to evolve, a long history of stable and unique environmental conditions are required. Some of these conditions are provided by the mountainous landscape of Barberton. Together with the unique geology, these mountains can also offer a suite of different climates, based on aspect and altitude, in close vicinity to each other. During climatic changes a plant or animal can escape to adjacent suitable refugia found in these mountains, allowing them to persist and speciate. The large number of diversity in this region, including endemic plants and animals, may serve as evidence of successful survival during historic changes. In order for species to survive, and to mitigate the current global warming event, these landscapes should be continuous, and undisturbed. Thus, the ecological infrastructure needs to be maintained.

Unfortunately, the reality is that large tracks of habitat have already been lost due to commercial forests, mining, farming, alien plant infestation, over-grazing and poor fire management.

There is no denying that some of the Barberton Centre’s plants are in trouble from the above impacts but also from global warming as species that flourish on the top of the mountains cannot escape any higher with an increase in temperature. It becomes a case of adapt or die.  The welfare of the plants there is managed and monitored by the  Mpumalanga Tourism and Parks Agency’s scientific services who gather and use information to study the effects of climate change and to identify priority areas for biodiversity in need of protection.

Some of the significant conservation areas around Barberton include the Songimvelo nature reserve (49 000 hectares), Nkomazi Wilderness (12 000 hectares), Mountainlands nature reserve (20 000 hectares), Barberton nature reserve (8 000 hectares), and several conservancies.  Smaller conservation areas include the Cynthia Letty, Tienie Louw and Thorncroft nature reserves, all three created primarily to protect rare species of aloe.

In 2008, Tentative World Heritage Site status, of which the Barberton Greenstone belt forms the core was received both nationally through the Department of Environmental Affairs and internationally through UNESCO, based on the global uniqueness of the exposed geological formations. This supports the area as having outstanding universal value for all humanity. Most of the reserves were also placed on the “National list of ecosystems that are threatened and in need of protection”. The internationally recognised Songimvelo-Malolotja Transfrontier Conservation Area, which stretches from Swaziland to the Barberton Mountainlands Nature Reserve also contributes to a north south conservation corridor that connects to the Kruger National Park.

South Africa’s endemic plants are concentrated in only a few places and the area around Barberton is one of three Centres of Floristic Endemism in Mpumalanga. The other two are the Wolkberg Centre and the Sekhukhuneland Centre. It’s clear that this mountainous hinterland is owned by plants – even though human intervention is needed to ensure their protection.

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