The Cape Floristic Region and the Succulent Karoo are two of the three widely known biodiversity hotspots of South Africa. They make out some of the wide range of biomes that are found here. Collectively Cape Flora is called fynbos, which embraces resilient, low-growing, small-leafed, evergreen shrubs. The moist, winter-rainfall region of the Fynbos Biome is in the south-west and the drier Succulent Karoo is located west and south of the Escarpment. The Succulent Karoo biome has the highest diversity of succulent plants in the world, and is the most rich in species diversity of all our semideserts. The Cape Floristic Region has an exceptional ecological floristic diversity with many endemic plant species. These two fascinating biomes share a boundary and a floristic similarity, which the moisture availability and geology determines (Cowling et al. 1997). Fire is very destructive in Succulent Karoo and prevents it from invading fynbos sites. The Succulent Karoo is the fourth largest biome in South Africa, with mostly flat terrain and an extreme altitudinal range. Globally there are few other places that can claim to be as biologically distinct as the Succulent Karoo Biome. Both biomes experienced numerous adaptive radiations and associated endemism for a wide range of faunal and floral groups. Although both biomes have many similarities, there is also great difference.
Biogeography
The Cape Floristic Region (CFR) covers about 90 000 km2 and possesses about 9000 different species within this range, with the endemnism of about 70% of all species (Linder H. , 2003). The Succulent Karoo covers approximately 100 000 km2. Most of the Cape receives an annual rainfall of 300 to 2000 mm per year, some areas as much as 3000mm (Deacon et al. 1992), where mists are mostly prominent in summer. The Succulent Karoo is a semi desert region with a low winter rainfall, arid summer and a mean annual precipitation between 100 and 200 mm. The Succulent Karoo has a very dependable precipitation in terms of predictability, this element of climatic stability directly influences the high species diversity (Desmet & Cowling 1999).
The length and temperature of the growing season differentiates the Succulent Karoo , short and cool, from Fynbos, long and cool. Succulent Karoo soils are finer-grained, less leached (due to aridity), and have a higher pH (>7) than fynbos soils (Ellis & Lambrechts 1986). Mole rats, lizards, tortoises, monkey beetles, scorpions, bee flies, bees and vespid wasps (Vernon 1999) have high concentrations of diversity and endemism in the Succulent Karoo. There are 115 species of reptiles in the Succulent Karoo of which 36 are endemic, mostly lizard species.
Botanically it is compositionally and singularly rich: home to 6356 species of vascular plants in 1002 genera and 168 families (Driver et al. 2003). Of which 26% (1630) of species are strictly endemic and 14% (905) are near endemics (Driver et al. 2003)and 17% are listed as Red Data species (International Union for Conservation of Nature 1994). There is a high diversity, 1700 species, of dwarf leaf-succulents shrubs (Driver et al. 2003), which is the Succulent Karoo's most distinctive character. The Cape Floristic Region contains many families of species (home to 9000 plant species)such as Ericaceous (comprised of about 3000 species), proteoid (330 species), restioid (310 species) and asteraceous fynbos. Where 68% of species, 20% of genera and 6 families are specifically endemic to this region. The Cape Peninsula alone has 165 endemics out of a flora of 2256 species. Ericaceous fynbos occurs at higher altitudes than proteoid fynbos, on permanently wet, cool and relatively fine-grained soils. Proteoid fynbos is widespread on the deep fertile soils at the foot of mountains, with deep roots that utilizes water unavailable to other fynbos plants, and develops when most other fynbos are dormant.
The wet season is the major flowering time. Restioid fynbos is dominated by shallow-rooted plants that occur on warmer, north-facing slopes that are on shallow soils, including dunes and perched sandy plateaus. Also found on waterlogged soils on cooler, south-facing slopes, where root growth is undeveloped mostly throughout the year. Asteraceous fynbos occurs on hot, lower, north-facing slopes, on the deeper soils. Talus asteraceous fynbos (waboomveld) is confined to lower slopes and talus slopes on fertile, deeper soils. Ericaceous and proteoid fynbos are more common on the coastal ranges, restioid and asteraceous fynbos prevail on inland ranges. Higher and wetter mountains have more ericaceous and proteoid fynbos. Flats and lower ranges are dominated by restioid and asteraceous fynbos (Campbell 1985).
Charismatic species
Succulent plants of the Succulent Karoo biome have the ability to absorb water during times of plenty (in tissues in the leaf, stem and root) for later use during droughts. Succulent species that stand out in the Succulent Karoo is the Kokerboom- Aloe dichotoma (Asphodelaceae) in Namaqualand which is not precisely a tree, but looks similar to one with its branches and leaves; Halfmens- Pachypodium namaquanum (Apocynaceae) which has short, thick stems with prickly surfaces and tufts of hard leaves, and strangely leans northward; as well as the Botterboom- Tylecodon paniculatus (Crassulaceae).
One spectacle that should definitely be seen in the Succulent Karoo is the spectacular spring flower displays. Many floristic plants display their beautiful flowers, some of these include Ursinia cakilefolia (Asteraceae) in Skilpad Flower Reserve; Grielum humifusum (yellow), Felicia namaquana (blue), Arctotis fastuosa (orange) in Goegap Nature Reserve near Springbok; and the very common Dimorphotheca species (the Namaqualand daisy).
Of the 630 geophytic species several Amaryllidaceae have rain-stimulated flowering. Which means that the flowers only open after it has rained, producing beautiful areas of colour. Such species are Brunsvigia, Haemanthus, Crossyne and Boophane.
On the ever present quartz patches, endemic species such as the flowering Argyroderma delaetii (Aizoaceae) near Knersvlakte and the dwarf stem succulent Dactylopsis digitata (Aizoaceae) are to be noticed.
Trees occur rarely in the Succulent Karoo. Only 35 tree species are present, which includes tree aloes and the evergreen, sclerophyllous tree Ozoroa dispar (Anacardiaceae) growing on granite domes.
The hallmark of the Succulent Karoo is the high diversity and strong dominance of dwarf to low, leaf-succulent shrubs such as the mesemb Astridia velutina.
The Cape Floristic Region (fynbos) is characterized by four growth forms. One is tall Proteoid shrubs with large leaves about 1-3 m in height with large leathery leaves such as Leucospermum, Mimetes, Aulax, and Protea. The second is a small, heath-like Ericoid shrub with fine leaves like Aspalathus (e.g. Rooibos), Agathosma (e.g. Buchu), Cliffortia and Phylica. Thirdly, reed-like Restiod plants e.g. Elegia, Restio, Thamnochortus, but also grasses and sedges. Lastly, bulbous herbs (geophytes) with beautiful flowering displays such as Disa, Lachenalia and Gladiolus, often these species are hysteranthus, with fire-stimulated flowering.
The Cape Peninsula also display flowering plants like Erica urna-viridis and Wurmbea marginata which are endemic and very unique looking.
A conservation symbol of the Fynbos Biome is the Bontebok, Damaliscus pyrgargus pyrgargus.
Representatives of the endemic and the near-endemic families of the Cape Floristic Region are plants such as Lanaria lanata (Lanariaceae), Grubbia rosmarinifolia (Grubbiaceae), Brunia albiflora (Bruniaceae), Roridula gorgonias (Roridulaceae), Retzia capensis (Stilbaceae), Saltera sarcocolla (Penaeaceae).
Two well recognized flowers are the king protea, Protea cynaroides, as the national flower of South Africa and the red disa, Disa uniflora. The Clanwilliam cedar, Widdringtonia cedarbergensis, is an elegant but diminishing conifer endemic to the Cederberg Mountains.
The Cape Floristic Region is home to bird species such as the Cape sugarbird, Promerops cafer, the orange-breasted sunbird, Nectarinia violacea, and the Protea canary, Serinus leucopterus.
There are approximately forty species of amphibians in the Cape Floristic Region, sixteen of which are endemic. The Table Mountain ghost frog, Heleophryne rosei, is endemic to four perennial streams on Table Mountain and is extremely endangered.
Threats
Human impacts on the fynbos vegetation are very severe, which is a consequence of the combination of overgrazing, cultivation, mining, pollution, deforestation and afforestation. Humans influence the structure and composition of vegetation by use of fire, harvesting food items, grazing by domestic animals, cultivation, alien plant introductions, and the harvesting of flowers and restioids (for thatching purposes)(Linder, 1990). The ecosystems differs topographically and geologically because not all landscapes and vegetation are used by humans to the same extent, such as less inhabited mountainous regions compared to excessively inhabited coastal lowlands.
Cultivation was first introduced by European colonists, who planted wheat, oats and grape vines. About 96% (Cowling R. &., 1992)of the original vegetation of the West Coast renosterveld was transformed mainly by agriculture (McDowell, 1988; Rebelo, 1997), now many rare and endangered species exist in this area. Alien plant infestation is relatively recent, most originate from intentional introductions between 1830-1900 (MacDonald 1986). The motives behind the introductions were for aesthetic purposes (Pinus spp.), construction materials (Eucalyptus spp.) and the stabilization of mobile sand (Acacia). The infestation of Hakea and Pinus species in 1984 was estimated to be 6641 km2, which intruded on 8.6% of the Fynbos biome and 12% of the area of natural vegetation. A few of the invasive species are Acacia cyclops, Acacia saligna, and Pinus pinaster (Richardson et al. 1996).
Fynbos ecosystems in the Southwest Centre have been transformed into vineyards, fruit orchards, and pine plantations to a great extent. Sand fynbos was demolished in the influx of the Cape Town metropolitan area, small holdings and alien plant invasions. The distribution pattern of threatened ecosystems is parallel to the distribution of threatened butterflies, amphibians, reptiles and plants. According to the Red Data, alien invasive plants are the biggest threat to biodiversity, followed by agriculture then urbanisation (Rebelo A. e., 2006).
In the Succulent Karoo there are less human population pressures, which results from farming, mining and urbanisation. Most of this biome area is used as a natural grazing form of land use. Climate change has been identified as a major threat seeing as global temperatures have already increased by 0.5ºC and the rainfall is expected to decrease in the next fifty years. A decrease in rainfall would be devastating to the Succulent Karoo biome because it would cause the environment to become even drier. Fragmentation or alterations of natural habitats (such as the cultivation of grapes, citrus, tobacco, alfalfa, and vegetables) leads to the extinction of species.
These plantations are dependant on good irrigation infrastructure which changes the natural habits of river valleys. Alien species invasions, disruption to pollinators, mining (diamonds, titanium, zinc, copper, gypsum, quartz), livestock grazing, game farming for ecotourism/hunting, boom in Ostrich farming industry, dryland farming, collectors of novelty fauna and flora, and the large scale uncontrolled harvesting of flora with medicinal value are all great concerns to the well being of the biodiversity. No less than 5% of vegetation has been lost to mining and agriculture, and about two-thirds of the area has acutely been overgrazed. An estimated 29% of the Succulent Karoo biome is in a relatively unspoiled condition.
Conservation status and strategies
A comprehensive action plan for fynbos and other vegetation types within the CFR has been completed and elaborated upon both regionally and nationally (PreslFey et al., 2003). In the 2000s, the Cape Action Plan for People and the Environment (CAPE) was established to affect conservation in the Fynbos Biome. One conservation plan is to built 'megareserves' focused on the existing conservation area in sandstone fynbos, but linking them to relatively unconserved renosterveld, karoo shrublands and sand fynbos of the lowlands (Rebelo A. e., 2006).
What looks to be a promising new project is an initiative 'Working for Water Programme', which is centred around the removal of alien plants by working with the communities around infected areas to remove invasive species. The project has created 3600 jobs and altogether has cleared around 500 km2 of alien growth. New protected areas such as the Cape Peninsula National Park, the West Coast Biosphere Reserve, and the Cape Agulhas National Park have successfully been established. Recently the Cape Floristic Region was declared a World Heritage Site with eight protects areas.
Only about 2560 km of the Succulent Karoo (2.5% of land area) is protected. The largest reserve is the Richtersveld National Park, administered by the community that lives there and the government (McGinley, 2008). A framework to guide conservation action in the Succulent Karoo has recently been completed by a team of regional experts funded by Conservation International. The Succulent Karoo Ecosystem Plan (SKEP; Driver & Maze 2002) has moved into implementation phase (Rebelo A. e., 2006). Public awareness of this biome is growing through the SKEP. SKEP is the result of a short planning exercise that combined scientific knowledge and land-user insight to identify a Conservation and Sustainable Land-use Strategy for the Succulent Karoo hotspot (McGinley, 2008). The reserve system through the Succulent Karoo is expanding by the creation of new parks such as the Namaqua National Park (600 km) in the central uplands of Namaqualand, the park is set to expand westwards.
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