CONSERVATION

​What is Succulent Karoo? An Introduction

OCT 05, 2020 | Written and photographed by Zoë Chapman Poulsen & Rupert Koopman. 

Above: Knersvlakte north of Vanrhysdorp. Photo: Rupert Koopman.

Succulent Karoo: An Arid Biodiversity Hotspot

Famous the world over for its extraordinary biodiversity, the Succulent Karoo biome is home to the richest succulent flora on earth. The area spans from Luderitz in Namibia in the north, through the Richtersveld, Namaqualand, Hantam, Tanqua, Roggeveld and eastwards into the Little Karoo.

At approximately 111 000 km in size, the Succulent Karoo is the fourth largest biome in southern Africa, smaller only than the savanna, Nama-Karoo and grassland biomes. It is bordered by the Fynbos Biome to the south and east, Albany Thicket in the east, Nama-Karoo to the north and west and the Desert Biome to the north.

Above: Pachypodium namaquanum at Karoo Desert National Botanical Gardens. Photo: Zoë Chapman Poulsen

Climate, Geology and Soils

The majority of the Succulent Karoo biome has a relatively mild climate with a strong maritime influence. Most of the region has winter rainfall, with the eastern Little Karoo experiencing year round precipitation. Mean annual precipitation for most vegetation units across the biome is from 100-200 mm. Some areas, including those adjoining the Namib Desert, experience less than 100 mm. The wettest part of the biome is the Robertson Karoo that received mean annual precipitation of almost 300 mm.

The mean annual temperature for the Succulent Karoo biome is 16.8 °C. In the lower lying coastal regions such as the Knersvlakte, frost is extremely rare. However, at higher elevations further inland such as the Roggeveld Karoo, frost is relatively commonplace, occurring on average around 60 days per year.

The Succulent Karoo Biome covers a large area and is known for its highly complex geology. The majority of the region occurs on shale geology from the Bokkeveld group of the Cape supergroup. The northernmost part of the region occurs on the geology of the Richtersveld Terrane, the Namaqua-Natal Metamorphic Belt and the Gariep Metamorphic Belt.

Above: Cheridopsis pillansii. Photo: Zoë Chapman Poulsen.

Flora & Wildlife

The Succulent Karoo is home to a total of around 6 350 species of vascular plants, of which nearly 2 440 (40%) are endemic to the biome, therefore meaning that they are found nowhere else on earth. Many plant species in the Succulent Karoo are notable habitat specialists, occupying very specific habitat niches. One of the most famous plant species from the Succulent Karoo are the ‘halfmens’ of the Richtersveld (Pachypodium namaquanum) that can grow up to 4m in height.

The Succulent Karoo has more than 225 bird species, 75 mammal species and more than 90 species of reptiles. Amphibians are relatively poorly represented due to the aridity of the region. There is one endemic bird, namely the Barlow’s Lark and two endemic mammals, De Winton’s Golden Mole and the Namaqua Dune Mole Rat. Invertebrate diversity is also high, with more than 70 scorpion species present.

Above: Evening in the Robertson Karoo. Photo: Rupert Koopman.

The Poaching Problem

The succulents that make the Succulent Karoo famous are sadly often targeted for illegal collection for the horticultural trade. It is illegal in South Africa to remove plants such as these from the wild without a permit and punishments for those caught can be severe. Please always ensure when purchasing plants for your garden that they are sourced from reputable growers who do not collect illegally from the wild. Read more about this in the September 2020 issue of Veld & Flora.

Above: Increasingly extreme drought conditions brought about by changing climate is already causing extensive mortality of perennial shrubs, trees and succulents in the Succulent Karoo of Namaqualand. Photo: Zoë Chapman Poulsen.

Impacts of the Climate Crisis

We are only just beginning to count the cost of the impacts of the world’s climate crisis on the flora and biodiversity of the Succulent Karoo biome. Across southern Africa temperatures are forecast to increase with the area projected to experience increasing aridity and longer and more extreme periods of drought.

These changes are already starting to have a devastating effect on the biodiversity of this hotspot. Scientists have observed mass mortality of succulents, perennial shrubs and trees in response to the extremes of drought the region has experienced in the last few years. It remains to be seen how these changes will further impact the region going forwards. Nick Helme and Ute Schmiedel take a closer look in the March 2020 Veld & Flora.

Conservation & Management

Life in this extraordinary semiarid landscape always takes place on the edge, with care needed by landowners as custodians of the Succulent Karoo to ensure that management and land use such as livestock grazing is in line with conserving the biodiversity of this unique and extraordinary part of South Africa. More detailed information about sustainable veld use and management for landowners can be found in the Karoo Veld: Ecology and Management book.

Above: Succulent Karoo vegetation along the R354 between Calvinia and Sutherland. Photo: Zoë Chapman Poulsen.

Collaboration in the Succulent Karoo    

At the recent McGregor Magic online Festival, Ismail Ebrahim (CREW) and Rupert Koopman (BotSoc) led a Bioblitz at Vrolijkheid Nature Reserve. Ismail’s video of the event can be seen here and Rupert’s summary of the initial results of the Bioblitz.

Further Reading

Esler, K.J. Milton, S.J. Dean, W.R.J. (Eds) (2010) Karoo Veld: Ecology and Management, Briza Publications, Pretoria, South Africa.

Helme, N. Schmiedel, U. (2020) ‘Namaqualand Nightmare’, Veld & Flora, Issue 106 (2), pp. 14-19.

Knoetze, L. (2020) ‘SA’s Great Succulent Robbery’, Veld & Flora, Issue 106 (3), pp. 24-29.

Mucina, L. Jurgens, N. le Roux, A. Rutherford, M.C. Schmiedel, U. Esler, K.J. Powrie, L.W. Desmet, P.G. Milton, S.J. (2006) ‘Succulent Karoo Biome’ in Mucina, L. Rutherford, M.C. (Eds) The Vegetation of South Africa, Lesotho & Swaziland, Strelitzia 19, South African National Biodiversity Institute, Pretoria, South Africa.

Vlok, J. Schutte-Vlok, A.L. (2015) Plants of the Klein Karoo, Umdaus Press, Hatfield, South Africa.