WOODBUSH GRANITE GRASSLAND (WGG)

 

What makes Woodbush Granite Grassland so special?

Woodbush Granite Grassland (WGG) is one of South Africa's 72 nationally recognized vegetation types (1) and is a declared critically endangered ecosystem. It occurs in the Limpopo Province on the Woodbush plateau at altitudes ranging between 1080 - 1800 m amsl (see the map below; 2). Only about 10 relatively undisturbed fragments of WGG still exist. Of these, the largest (about 190 ha) is situated next to the small town of Haenertsburg, to the south and west of the village, where the bulk of it is formally protected in the Haenertsburg Nature Reserve. Apart from these few unspoilt fragments, the WGG vegetation unit is severely transformed, overgrazed and infested with unmanaged alien invasive vegetation.

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Only about 6% of the area once covered by WGG, remains untransformed.

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Rich plant and animal diversity

Although visually dominated by grasses, grasslands are among the most species rich plant communities in South Africa; only one in every six plant species is a grass! For this reason, though WGG might appear to be a homogenous landscape, closer inspection reveals exceptionally high botanical diversity. Plant taxonomist Pieter Winter (SA National Biodiversity Institute) has previously identified over 600 different indigenous plant species within WGG. The most recent figure stands at 661 indigenous plant species (3). Associated with this rich botanical diversity, is a diverse indigenous faunal composition consisting of an extensive list of mammals, birds, reptiles, amphibians and invertebrates. Among these floral and faunal species, many are protected, endemic, rare or threatened. Unfortunately, some species are also presumed extinct, either locally from a particular WGG patch, or completely as is the case for the poker plant Kniphofia crassifolia. Eastwood´s Longtailed Seps (Tetradactylus eastwoodae), a species of lizard in the family Cordylidae, was last seen more than a century ago. As a critically endangered vegetation unit, remaining portions of undisturbed WGG faces a very high risk of irreversibly transformation. If we want future generations to see and enjoy the biodiversity contained within WGG, every effort must be made to conserve it.

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As a critically endangered vegetation unit, remaining portions of undisturbed WGG faces a very high risk of irreversibly transformation.

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Northern forest rain frog (Breviceps sylvestris)

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Gaudy commodore (Precis octavia)

Species name

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Source of traditional plants

Several plants within the WGG have important medicinal, cultural and nutritional value for local rural communities. A large percentage of South Africa’s population uses traditional medicine for primary health care, which has led to a buoyant trade in the plant material used for this purpose. Unfortunately, the continuous loss of natural areas is also threatening this practice and at the same time putting strain on the remaining grassland fragments. According to a recent ethnobotanical study, 18% of WGG indigenous plant species possess medicinal properties. The study also lists the 20 top ranking medicinal plants that are sourced from WGG (3). Most of the material used for medicinal and other purposes, are from wild harvested plants. Bush tea (Athrixia phylicoides) and the ever popular “Broom Asparagus” (Asparagus virgatus) is collected in large quantities, yet sustainably, and provide a critical income to some of the poorest people in Limpopo. The protection of WGG plays a key role in ensuring that this natural heritage is protected and managed correctly for both present and future generations.

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Bush tea (Athrixia phylicoides) and “Broom Asparagus” (Asparagus virgatus) is collected in large quantities, yet sustainably, and provide a critical income to households within Limpopo's rural communities.

Pineapple lily (Eucomys automnalis)

Important water catchment area​

The WGG together with the local indigenous forests form a critically important water production landscape. The grassland is particularly important as it acts as a sponge, steadily releasing water into streams and rivers that feed into dams. The grassland next to Haenertsburg feeds into the Ebenezer Dam, which supplies potable water to Haenertsburg, Polokwane and rural villages in the Mankweng area. Ebenezer Dam further supplies water to the agricultural sector in the Lowveld via the Tzaneen Dam. It has been estimated that any further developments in Haenertsburg would pollute the catchment if they relied on septic tanks and a sewage plant would be needed.
 

View of the Ebenezer dam from the peninsula

Protection status

In 2006, WGG is described as the most threatened vegetation unit in the Limpopo Province, Republic of South Africa (RSA; 4). Only about 6% of the area once covered by WGG, remains untransformed (5). In 2011, WGG was officially declared a critically endangered ecosystem on the list of national threatened terrestrial ecosystems in the Government Gazette No. 34809 (6). In 2016, the Haenertsburg Nature Reserve (HNR) was established and serves to formally protect the bulk of one of the largest intact remnants of this magnificent vegetation type. At present, FroHG is partnering with the Limpopo Department of Economic Development, Environment and Tourism (LEDET), and with the Kruger to Canyons Biosphere Region NPC, to formulate a management plan for the HNR.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Aerial view overlooking a section of the Haenertsburg Nature Reserve, with the Ebenezer Dam in the background enveloping a portion of Woodbush Granite Grassland on the peninsula.

 

Main threats to Woodbush Granite Grassland

Transformation

  Either through development, farming or plantations

Invasive alien vegetation

  Alien invasive species are fast spreading, out-compete native flora and change the soil composition.

Illegal or Unsustainable harvesting of medicinal plants

  Demand for medicinal plants with a growing human population could put strain on this fragile vegetation type. 

Encroachment by woody plants

  Without native grazing animals and natural occurring fires woody plants tend to take over.  

Illegal grazing

  Illegal grazing by domesticated grazers.

Human activity

  Littering, dumping of garden refuse in the grassland, driving on the grassland, illegal fires, removal of protected species, etc.

Climate change

References

1Mucina L and Rutherford MC (Eds). 2006. The vegetation of South Africa, Lesotho and Swaziland. Strelizia 19. South African Biodiversity Institute, Pretoria.

2South African National Biodiversity Institute (2006-2018). The Vegetation Map of South Africa, Lesotho and Swaziland, Mucina L, Rutherford MC and Powrie LW (Eds.), Online, http:bgis.sanbi.org/Projects/Detail/186, Version 2018.

3Dzerefos CM, Witkowski ETF and Kremer-Köhne S (2017). Aiming for the biodiversity target with the social welfare arrow: Medicinal and other useful plants from a Critically Endangered grassland ecosystem, Limpopo Province, South Africa. International Journal of Sustainable Development and World Ecology 24, 52–64.

4.  Rouget M, Jonas Z, Cowling RM, Desmet PG, Driver A, Mohamed B, Mucina L, Rutherford MC and Powrie LW 2006. Ecosystem status and protection levels of vegetation types. In: Mucina L and Rutherford MC (Eds) The Vegetation of South Africa, Lesotho and Swaziland. 724–737. Strelitzia 19. South African National Biodiversity Institute, Pretoria, South Africa.

5.  Niemandt C and Greve M (2016). Fragmentation metric proxies provide insights into historical biodiversity loss in critically endangered grassland. Agriculture, Ecosystems and Environment 235, 172–181.

6.  National Environmental Management: Biodiversity Act: National list of ecosystems that are threatened and in need of protection, Notice 34809, GN 1002, 9 December 2011.