Flora of the Western Cape

    The Western Cape Province of South Africa is part of what used to be called the Cape Province which made up almost half of the country.  That area was subsequently divided into the Western Cape, the Eastern Cape and the Northern Cape, each with its own provincial premier and legislature. The Western Cape is centered around the city of Cape Town and is more or less crescent-shaped, with the flank of its northern horn facing west toward the Atlantic and the flank of its eastern horn facing south toward the Indian Ocean.  The population of the Western Cape is approximately 5.3 million with Afrikaans being the rincipal language spoke. The Western Cape Province shares with Southern California the distinction of being among the five regions of the world which harbor what is referred to as Mediterranean vegetation, the others being southwestern Australia, western Chile, and of course, the coastal Mediterranean.  It is obviously no coincidence that these regions have developed similar types of vegetation, because even a cursory glance at a world map reveals that all of them are situated approximately the same distance from the equator, with Chile, South Africa and Australia being between 30° and 40° south of that line, and Southern California and the Mediterranean being between 30° and 40° north of it, and all of them are either on the western edges of continents or are influenced by prevailing winds from the west.

    The Cape Floral Kingdom or Floristic Region is the smallest of the six such natural areas in the world, and is the only one contained within the borders of a single country. The others are the Boreal or Paleoarctic, Australasian, Neotropic, Paleotropic, and Antarctic.  The Antarctic kingdom, although itself quite small, is nevertheless some 25 times as large. The CFK comprises less than 0.04% of the earth's land surface, yet harbors 3% or 4% of the world's species.  All of tropical Africa contains some 30,000 plant species in almost 20 million square kilometres, which is only 3.5 times as many species in an area 235 times as large.  The British Isles, at 3.5 times as large as the CFK, has only 1,500 species compared to the Cape's 8,600.  And it is not merely its botanical diversity and richness that is significant.  Almost 70% of its species are found nowhere else on earth. Unfortunately, almost three-quarters of all the species in South Africa's IUCN Red Data book of threatened or endangered species are currently growing in this Floral Kingdom, and this means that hundreds of species are facing extinction.


    Let us be clear here on what areas we are talking about.  The terms Western Cape Province, Cape Floral Kingdom (or Floristic Region or Province), and fynbos biome are often confusing, and were to me before I started writing this.  They don't refer to exactly the same thing.  The Western Cape Province is a specific bordered area that stretches about 375km north and about 480km east of Cape Town.  The fynbos biome comprises the majority of the Cape Floristic Region, but does not include those areas of so-called succulent karoo vegetation in the far northern region of the Western Cape Province, those areas of nama karoo vegetation in the northeastern part of the Province, and some small patches of sub-tropical thicket and afromontane forest primarily in the Eastern Cape Province, all of which are properly considered part of the Cape Floral Kingdom (see map).  It should also be pointed out that both the Cape Floral Kingdom and the fynbos biome extend well beyond the boundaries of the Western Cape all the way to Port Elizabeth in the Eastern Cape.  The Cape Floral Kingdom thus occupies virtually the entire Western Cape Province, a small area in the western part of the Eastern Cape Province, and some very tiny sections of the Northern Cape Province adjacent to the Western Cape. Percentagewise, about 70% of the CFK and fynbos vegetative area is in the Western Cape, about 25% in the Eastern Cape, and about only about 5 % in the Northern Cape.

    The primary vegetation type of the Western Cape is fynbos, a term derived from Dutch and Afrikaans words meaning "fine bush," which typically grows on fairly nutrient-depleted mostly sandstone-derived acidic soils and is dominated by sclerophyllous, that is, evergreen, hard-leaved, flowering shrubs, many of which are proteas, ericas, cape reeds (Restios) , and geophytes (bulbed plants).  Fynbos is technically described as a vegetation that has more than a 5% cover of Restios and exists in a fire-controlled ecosystem characterized by significant winter rainfall, nutrient-poor soils, and exceptional floristic richness and endemism.  While two basic types of fynbos, mountain fynbos and lowland fynbos, have been described, references are often made to coastal fynbos on sandy alkaline soils and limestone fynbos.  In fact, one authority has categorized fynbos into five separate vegetative types, and there is no doubt that fynbos communities in different areas are not exactly the same depending on season, soil, slope, altitude and rainfall.  However, although they may not contain precisely the same species, they are structurally very similar. Lowland fynbos has perhaps more annuals and grass species, and is limited for the most part to sandy, clay or limestone soils.  In addition to sandstone-derived soils, mountain fynbos may grow where rainfall is sufficiently high on leached soils derived from granites or even shales. Trees are relatively rare in mountain fynbos but some that do grow there are the Clanwilliam cedar, the silver tree, the wild olive and the mountain cypress.  It is certainly to be suspected that the distinction between these two vegetative types is to some extent an artificial one, and obviously one can keep dividing areas into smaller and smaller sub-units almost indefinitely. Fynbos makes up about 80% of all the vegetation of the Cape Floral Kingdom, and it clearly bears a striking similarity to Southern California's chaparral, but due to the relatively poor quality of the soil, the shrubs are generally smaller and spaced farther apart, making it easier to move through than is the case with chaparral.  Like our chaparral, this vegetative type is well adapted to fires, and even requires a cycle of fires of from six to forty-five years to prevent the plants from aging and degenerating, and allowing the invasion of thicket and forest.  It is not necessary here nor will I attempt to delineate any differences between the various fynbos types or plant communities, but let it suffice to say that of the approximately 8,600 species in the Cape region, some 7,000 of them are present in the fynbos biome.  Thus the relationship between the fynbos biome and the Cape Floral Kingdom is sufficiently great that they can be forgiven who associate the two as one.

    A second vegetation type within the fynbos biome that superficially resembles fynbos is called renosterveld and is found in both in the coastal lowlands and the mountains, and dominated to some extent by the renosterbush, Elytropappus rhinocerotis, in the Asteraceae family. Renoster means rhinoceros in Afrikaans, and is probably a reference to the historic habitat of the black rhino.  In the past, because of its richer soils, which are generally more fine-grained clays or silts, renosterveld supported quite extensive populations of many of the large species of animals such as cape buffalo, elephant, rhino, eland, zebra, lion and cheetah, but those animals are mostly gone now except where they have been reintroduced. Also because of its more fertile soils, much of the renosterveld area has been agriculturalized.  There is a great species richness of geophytes, especially irises, lilies and orchids. Generally speaking, renosterveld lacks the Restios (although grasses are abundant), and proteoids are either absent or quite uncommon.  Fairly low ericoid shrubs with small, tough leaves predominate, with a lower layer of the grasses and seasonally-active geophytes.  The Asteraceae is one dominant family.  Rainfall in areas harboring this veld type is usually from 25 to 60cm a year. Where rainfall is higher, renosterveld is replaced by fynbos, and where lower by succulent karoo. Like fynbos, renosterveld is fire prone, and has been referred to as the most endangered vegetation type in the Cape Floral Kingdom.

    The species density and diversity throughout the Western Cape is highly extraordinary.  Although geographically the Cape Floral Kingdom occupies less than 5% of the area of South Africa, more than 40% of all South African plants are to be found there.  There is one report of 121 species being recorded for an area of 100 square meters!   The largest family is the Asteraceae with over 1000 species, the largest genus of which is Senecio. There are roughly 765 species of Ericas, 624 species of Irises, 728 species of Mesembryanthemums, 606 species of legumes, 322 species of Proteas, 315 species of Cape Reeds, and 220 species of orchids (see table). These figures are higher than in the table, because it is from 1984.  Table Mountain itself is home to almost 1,500 species, more than the entire United Kingdom.  The reason for this incredible diversity appears to lie primarily in the topographic and climatic variety which characterizes the Western Cape Province. The convergence of the Atlantic Ocean and Indian Ocean weather systems, as well as a multiplicity of topographic features such as coastal plains, narrow valleys, high plateaus and steep escarpments, has conspired to create an enormous array of habitats and microclimates within which these many thousands of species have evolved.  

    Other factors leading to a high floristic diversity are a complex rainfall pattern with precipitation amounts ranging from 20cm to 200cm, varied soil types, the frequency of fires producing in some reseeding species shorter generational times and thus higher speciation rates, the evolution in many species of short seed dispersal distances, a significantly higher pollinator diversity, and, perhaps as important as any of these, a relatively stable climatic history throughout the Pleistocene era which resulted in lower extinction rates and relatively more numerous local speciation events. Beyond this, many of the fynbos species have had to adapt to the harsh nutrient-deprived soils, and this accounts in large degree to the high level of endemism which is prevalent throughout the Cape.  The region's peak blooming season is in the spring months of September and October, but there are numerous species in bloom throughout the year. It is interesting to note for Southern Californians that we share quite a few genera with South Africa, among which are Acacia, Apium, Asclepias, Clematis, Cotula, Crassula, Cuscuta, Euphorbia, Geranium, Hibiscus, Limonium, Linum, Lobelia, Lycium, Oxalis, Pellaea, Polygala, Polygonum, Psoralea, Ranunculus, Rhus, Salvia, Senecio, Silene, Solanum, Stachys, Typha and Viola.

    The great majority of species of genus Erica in the world are endemic to South Africa.  Most of these are smallish shrubs with small, needle-like, often down-rolled leaves with the stomata being positioned inside a very narrow slit, upper surfaces which are hard and waxy, and delicate tubular flowers  The leaf characteristics are fairly common features of the Ericas and are an adaptation to minimize water loss.  Erica flowers have eight anthers and four petals joined to form a tube or cup. Another characteristic of the Ericas is that they have evolved a symbiotic relationship with fungi which helps them to maximize nutrient absorption in the relatively deprived soils of the Cape. About 80% of the Ericas are insect-pollinated, and the pollinators are often flies. It is speculated that the Ericas evolved after the breakup of Gondwanaland because they do not appear in either South America or Australia.   There are some 650 species of Ericas in the Cape Province, giving them the highest degree of regional speciation on earth.

     Proteas however are represented by fossil pollen found in Antarctica and by living species in Central and South America.  Their two most important centers of distribution are South Africa and Australia, so they almost certainly did evolve before Gondwanaland broke apart.  They derive their name from the Greek sea god Proteus, who had the power to take on a great variety of shapes, alluding to the great diversity within this family.  Unlike the Ericas, Proteas are generally shrubs with broad leaves and are mostly bird-pollinated.  They are also characteristically deep-rooted, and they all have somewhat woody stems. What appears to be the protea flower is actually, like a sunflower, a flowering head made up of many long, slender flowers surrounded by colorful bracts.  Protea flowers do not have separate petals and sepals. Instead, they have what are sometimes referred to as tepals.  The manner in which the tepals separate after the bud opens and the extent to which they remain fused at the base are characteristics which identify the various genera.  The anthers do not have long filaments, but are attached near the top of the tepals, shedding their pollen onto the uppermost portion of the style just before the flower opens. Some species have four small nectaries situated at the base of the ovary which secrete nectar to attract pollinators.  Proteas develop small dry fruits each containing a single seed.  Some genera like Leucadendron have the sexes separated onto separate plants. (See protea illustration)  


    The third major component of the Fynbos plant community is the Restionaceae, also an old family that evolved in Gondwanaland.  Of the approximately 480 species in the world, about 330 species inhabit the Cape region.  These rush-like plants thus occupy the position of the grasses that are so prevalent elsewhere.  The Restios are shallow-rooted with highly reduced dry, brownish leaves, and grow in clumps with the taller species being about waist high.  Most of the species are dioecious. The flowering spikelets at the ends of the stems typically give the landscape a greenish-brown look. The stems or culms are green, mostly solid, and perform the work of photosynthesis for the plant. The leaves are reduced to sheaths some of which are persistent, and some of which drop off, and are positioned at nodes along the stem.  The male plants bears cones with pollen, while the female plants have cones with feathery stigmas to collect the pollen.  Among the genera in this family represented in the Cape are Elegia, Ceratocaryum, Restio, Cannomois, Rhodocoma, Calopsis, Chondropetalum, and Thamnochortus. (See restio illustration)

    Fynbos is not the only plant community of the Cape Floral Kingdom. Another community is called strandveld, or beach vegetation, and is composed primarily of a shrubby flora found on sandy, well-drained and lime-rich soils.  It is to be found mainly along the Atlantic coast north of Cape Town.  This plant community is made up largely of succulents, bulbed geophytes, annuals and so-called cape reeds or Restios, members of the Restionaceae family, which have already been described.  Strandveld contains a lower species diversity and a smaller proportion of endemics, and may more properly be considered as a transitional vegetation type between fynbos and succulent karoo. There are also areas of woodland and forest containing such trees as Leucadendron argenteum, the silver tree, but these are not extensive.

    There are also other biomes within the Cape Floristic Region, and botanists have referred to these as subtropical thicket, succulent karoo and afromontane forest.  Let me reiterate that a biome is a major distinct ecological community type or a biophysiological grouping of species of plants and/or animals living together.  It is the highest level of plant community, representing a large and relatively uniform natural area, characterized by uniform vegetative life forms closely related to and more or less governed by climate. Succulent karoo is a biome which is not fire prone like fynbos or renosterveld, and exists in areas of flat to gently undulating plains with some hills and broken veld or grassland which supports a vegetation of small, succulent-leaved shrubs including many species of Aizoaceae, Mesembryanthemaceae, Crassulaceae and Asteraceae.  There are numerous annuals in spring and grasses are rare. The soils in this biome are lime-rich and weakly developed.  Rainfall varies from about 2cm-25cm and summer temperatures are quite high.  There is substantial species richness, and a large number of rare and Red Data Book species present.  Little of the area has been conserved, but fortunately there are few invasive alien plants.  Lack of water results in low agricultural potential.  Subtropical thicket is a fairly dense, more-or-less closed semi-succulent and spinescent evergreen shrubland to low forest, often almost impenetrable, generally not stratified and with little herbaceous cover.  It is present in river valleys, on rock screes and coastal dunes.  Rainfall in this biome is too low to produce a genuine forest, yet some degree of fire protection does exist. Most of the floristic components of thicket are present in other biomes and there are few species endemics.  It is in some senses a transitional community.  The afromontane forest is a biome consisting of patches of closed-canopy, evergreen trees which are afforded a large degree of fire protection by the high humidity and rainfall that ranges from 70cm to 200cm.  In the Western Cape it occurs mostly on south-facing ridges and in ravines, but would likely spread into at least some fynbos areas if it were not for the frequency of fires there.  Soils are generally well-developed and may be quite deep in lower valleys.  An understory often exists which is multi-layered and can include many lianas and epiphytes, however ground cover is typically lacking due to a high amount of shade.  Two tree species which have been harvested in the past are the black stinkwood, Ocotea bullata, and the Outeniqua yellowwood, Podocarpus falcatus.

    Up until about 5 million years ago subtropical vegetation was prevalent in the Cape area, but by that time the glaciation of the Antarctic continent was complete, the cold Benguela current was influencing the Cape and a Mediterranean climate pattern of moist winters and hot, dry summers had become established, allowing fynbos vegetation to move into the area from where it had existed previously further north.  At present, the greatest amount of rainfall is in coastal areas, growing drier as one proceeds inland. Much of the Western Cape receives from 25-63cm, but there are areas near Cape Town and along the Indian Ocean from Mossel Bay to Port Elizabeth that receive over 100cm, and yearly rainfall amounts as high as 200cm or even 300cm in some mountain areas are not unknown.  Temperatures range from 50°-60° in the coolest months in lower-lying coastal regions to 60°-70° in the hottest months, and are both cooler in the winter and hotter in the summer in higher elevations and farther from the coast.  The "tablecoth" on top of Table Mountain can add as much as 50cm of moisture per year, and fog along coastal areas is also an additional source of moisture.

     Many of the species presently inhabiting this region are threatened by extinction.  Three-quarters of the plants listed in the latest edition of the South African Red Data Book are in the Cape Floral Kingdom.  The coastal area has been subject to the multiple pressures of development, population growth, agriculture, plant collectors and the spread of invasive, alien plants.  It is certainly a great pity that only a very small percentage of this area has received any form of protection, but soon after I was there in 1998, the Cape Peninsula National Park was established and now preserves a very significant expanse that stretches some 60 km from Cape Town all the way to the tip of the Cape of Good Hope.  The Cape Floral Kingdom and the floristic biomes which it encompasses are a natural treasure for the people of South Africa and the world, and it is devoutly to be hoped that more areas will be set aside so that many of these endangered species will not be forever lost.

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