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Megadiverse Country: Introducing South Africa’s biodiversity hotspots

Jul 6, 2020  |  Written by Zoë Chapman Poulsen. Photos by Isobel Johnson and Zoë Chapman Poulsen.

South Africa is a country that is world famous for its extraordinary biodiversity. Recognised as one of the earth’s 17 megadiverse nations which combined contain two thirds of the world’s plant diversity, South Africa sits in the top ten nations for plant species richness worldwide. This is as a result of the country’s highly varied climate, topography and geology, which also has led to extremely high levels of endemism across its many different ecosystems, meaning that many South African species are found nowhere else on earth.

Perhaps one of South Africa’s most famous centres of plant diversity is the Fynbos Biome or Cape Floristic Region, which is one of the world’s biodiversity hotspots. However, few realise that South Africa is in fact home to three different biodiversity hotspots, namely the Cape Floristic Region, the Succulent Karoo ecoregion and the Maputaland-Pondoland-Albany corridor. Biodiversity hotspots are the world’s most biodiverse and threatened terrestrial regions. For an area to qualify it needs to have a minimum of 1500 species of endemic vascular plants and to have lost a minimum of 70% of its primary vegetation. There are 37 biodiversity hotspots worldwide, of which 8 are found on the African continent. In this week’s edition of the BotSoc Blog we are taking a look at South Africa’s biodiversity hotspots and what makes them special.

Cape Floristic Region Hotspot

Above: Fynbos in the Akkadiesberg above Stanford. Photo: Zoë Chapman Poulsen

 

The Cape Floristic Region (CFR) is perhaps South Africa’s most famous biodiversity hotspot. It is also recognised as a UNESCO World Heritage Site, owing to its extraordinary vascular plant diversity at all taxonomic levels. In recent years the Cape Floristic Region has been expanded to become the Greater Cape Floristic Region, with the previous extent of the CFR now being known as the Core Cape Subregion. The Core Cape Subregion (CCR) is 90 760 km2 in size and has around 9 383 known species of vascular plants. A total of 68% of these species are endemic to the area, therefore meaning that they are found nowhere else on Earth.

 

Above: Watsonia coccinea in bloom in newly burnt fynbos vegetation. Photo: Zoë Chapman Poulsen.

 

The CFR comprises a variety of different vegetation types. The most well-known and well-researched of these is fynbos. Fynbos is a Mediterranean type shrubland that is both fire prone and fire dependent. It is dominated by plants from three key plant families: The Proteaceae family, the Restionaceae family and the Ericaceae family. The less well-known renosterveld differs from fynbos by consisting of predominantly Asteraceous shrubs and grasses with an extraordinary diversity of geophytes that produce spectacular flowering displays during spring. On the coastline of the CFR we find strandveld, which has strong floristic links with subtropical thicket vegetation. The CFR also includes small patches of forest growing in sheltered areas with relatively high moisture availability where it is sheltered from fire.

Succulent Karoo Hotspot

Above: Succulent Karoo vegetation, Ou Tiep Farm, between Garies and Soutfontein, Namaqualand. Photo: Zoë Chapman Poulsen.

 

The Succulent Karoo Biodiversity Hotspot is one of two arid biodiversity hotspots located in predominantly winter rainfall semidesert. Extending northwards into Namibia along the West Coast of South Africa, the Succulent Karoo encompasses the regions of Namaqualand and the Little Karoo, the latter of which lies in a valley between the Swartberg mountains in the north and the Langeberg and Outeniqua mountains in the south. The Succulent Karoo is known for being home to the world’s highest diversity of succulent plant species. A total of 40% of the Succulent Karoo’s 6 356 plant species are endemic to the region and found nowhere else on earth. The area is also known for its high reptile and invertebrate diversity.

 

Above: Pelargonium echinatum. Photo: Zoë Chapman Poulsen.

 

The Succulent Karoo ecoregion has highly diverse geology owing to its complex geological and geomorphological history. However, the majority of the vegetation occurs on shale. Members of the Aizoaceae family, more commonly known as ‘vygies’ form a significant component of the flora, with their colourful daisy-like flowers. After flowering they form seed capsules that open upon contact with moisture from rainfall, flinging the seeds away from the parent plant into the veld. Few realise that geophytes also form a significant part of the Succulent Karoo’s flora, comprising 18% of the flora.

Maputaland-Pondoland-Albany Hotspot

Above: Grassland and forest in the mountains near Barberton on the border with eSwatini. Photo: Zoë Chapman Poulsen.

 

The Maputaland-Pondoland-Albany biodiversity hotspot is found on the east coast of South Africa below the Great Escarpment. Encompassing three of South Africa’s centres of endemism, it extends northwards from the Eastern Cape, also including the countries of eSwatini and Mozambique. There is considerable climatic variation from subtropical/tropical in parts of the hotspot in the north and nearer to the coast, ranging to more temperate with winter frosts in more inland higher altitude areas. The Maputaland-Pondoland-Albany hotspot is an important centre of plant diversity for South Africa, being the second richest floristic region in Africa after the Cape Floristic Region. Vegetation types of the area encompass subtropical thicket, which is an endemic vegetation type to the Maputaland-Pondoland-Albany hotspot, forest and grassland.

 

Above: The iconic Christmas Bells (Sandersonia aurantiaca) Photo: Isobel Johnson.

 

The area is home to almost 8100 plant species from 243 families in an area approximately the same size of New Zealand, of which nearly a quarter (more than 1900 species) are endemic to the area. There are 39 different genera which are endemic to the area and one endemic plant family, namely the Rhynchocalycaceae, which comprises the single monospecific species Rhynchocalyx lawsonioides which is found in southern KwaZulu-Natal and the Eastern Cape. It is listed as Near Threatened on the Red List of South African Plants due to firewood harvesting, alien plant invasion and inappropriate fire regimes. Another well-known endemic of the region is the iconic Christmas Bells (Sandersonia aurantiaca), which is now becoming increasingly rare due to habitat degradation, flower picking and forestry.

 

Further Reading

Bergh, N.G. Verboom, G.A. Rouget, M. Cowling, R.M. (2014) ‘Vegetation types of the Greater Cape Floristic Region’ in Allsop, N. Colville, J.F. Verboom, G.A (Eds) Fynbos: Ecology, Evolution and Conservation of a Megadiverse Region, Oxford University Press, UK.

Manning, J. & Goldblatt, P. (2012) Plants of the Greater Cape Floristic Region: Volume 1: The Core Cape Flora, Strelitzia 29, South African National Biodiversity Institute, Pretoria, South Africa.

Mucina, L. Rutherford, M (Eds) (2006) The Vegetation of South Africa, Lesotho and Swaziland, Strelitzia 19, South African National Biodiversity Institute, Pretoria.

 

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