Cape Peninsula

Geology

The Cape Peninsula is underlain by the oldest rocks in the area, the Malmesbury Group, and the granite intrusions of the Peninsula pluton.

The Malmesbury Group has been dated from between 830 and 980 Mya, and was deformed during the Saldanian orogenic cycle, both before and during the granite intrusions of 630 to 500 Mya, and there are minor intrusions which precede the granite. The base of this group has not been exposed. The basal rocks were eroded to a relatively featureless peneplain with exposed granites covering most of the peninsula south of Lion's Head and Devil's Peak. The Sea-Point contact zone, described by Charles Darwin is a well known region of metamorphic rocks formed by the granite intrusion into the Malmesbury rocks.

These rocks were later unconformably covered by the Cape Supergroup, which is divided into eight formations, the three oldest of which are present on the Peninsula. The lowest present is the reddish Graafwater formation which consist of shales and sandstone. The Graafwater Formation can be clearly seen in the cutting on the second hairpin bend as the Ou Kaapse Weg (road) goes up the slope from Westlake on to the Silvermine plateau. In the cutting one can also see the abrupt and obvious transition into the Table Mountain Sandstone (or, as it is currently known, the Peninsula Formation Sandstone) above it. Looking up the slope from below to the first hairpin bend, the granite basement on which the Graafwater formation rests is visible. And in the cutting at the first hairpin bend, the ocher-colored, gritty clay into which the granite weathers is clearly displayed. The relatively thin Graafwater layer (no more than about 60–70 m thick on the Cape Peninsula) is overlain by the prominent Peninsula Formation, which consists mainly of hard, erosion resistant, quartzitic sandstones, which form the high, prominent, almost vertical cliffs of the Cape Peninsula. At the very top of Table Mountain, at Maclear's Beacon, is a small remnant of the Pakhuis Diamictites, better represented in the Cederberg Mountains, 200 km to the north of Cape Town.

Soils

The soils of the Cape Peninsula are similar to those of other parts of the Cape Fold Belt, being derived from similar rock, and are mainly sandy and poor in nutrients. The poorest soils are those associated with the sandstone plateaux and upper slopes, which are grey, acidic, leached and generally shallow. They are mostly well drained, but there are areas of poor drainage on the relatively level plateaux and high ground which get winter rains and south-Easter cloud precipitation in summer, which are very acidic and have a high content of organic matter. The deeper soils of the colluvial slopes which are underlain by shale or granite tend to be heavier, orange to red, less acid and richer in nutrients. Soils associated with older Quaternary deposits tend to be fairly deep, moderately acid and more fertile than the soils derived from the sandstones. Younger sands along the coastline are alkaline and poorly consolidated.

Oceanography

The Cape of Good Hope is sometimes erroneously identified as the meeting point of the Atlantic and Indian Oceans. However, according to the International Hydrographic Organization agreement that defines the ocean boundaries, the meeting point is at Cape Agulhas, about 200 kilometres (120 mi) to the southeast and the most southerly tip of the African continent. The west coast of the Peninsula is referred to as the "Atlantic Coast" or "Atlantic Seaboard", but the eastern side is generally known as the "False Bay Coast".

Similarly, Cape Point is not the fixed "meeting point" of the cold Benguela Current, running northwards along the west coast of Africa, and the warm Agulhas Current, running south from the equatorial region along the east coast of Africa. In fact the south flowing Agulhas Current swings away from the African coastline between about East London and Port Elizabeth, following the edge of the Continental shelf roughly as far as the southern tip of the Agulhas Bank, 250 km (155 miles) south of Cape Agulhas. From there it is retroflexed (turned sharply round) in an easterly direction by the South Atlantic, South Indian and Southern Ocean currents, known collectively as the "West Wind Drift", which flow eastwards round Antarctica. The Benguela Current, on the other hand, is an upwelling current which brings cold, mineral-rich water from the depths of the Atlantic Ocean to the surface along the west coast of southern Africa. Having reached the surface it flows northwards as a result of the prevailing wind and Coriolis forces. The Benguela Current, therefore, effectively starts at Cape Point, and flows northwards from there, although further out to sea it is joined by surface water that has crossed the South Atlantic from South America as part of the South Atlantic Gyre. Thus the Benguela and Agulhas currents do not strictly "meet" anywhere, although eddies from the Agulhas current do from time to time round the Cape to join the Benguela Current.

Tidal range is moderate, with about 1.8 to 1.9 m range at spring tide on both sides of the peninsula, and tidal currents are negligible.

Bathymetry

The Bathymetry of False Bay differs in character from the west side of the Cape Peninsula. The west coast seabed tends to slope down more steeply than in False Bay, and although the close inshore waters are also shallow, the 100 m contour is mostly within about 10 km of the west coast, while the entire False Bay is shallower than about 80 m. The bottom of False Bay slopes down relatively gradually from the gently sloping beaches of the north shore to the mouth, and is fairly even in depth from east to west except close to the shorelines.

Navigational hazards

• Albatross Rock 34°16.527′S 18°22.210′E / 34.275450°S 18.370167°E
• Anvil Rock 34°22.218′S 18°31.090′E / 34.370300°S 18.518167°E
• Batsata Rock
• Bellows Rock 34°23.375′S 18°29.425′E / 34.389583°S 18.490417°E
• Cape Point
• Roman Rock
• Vulcan Rock

Climate

Much of the Western Cape has a Mediterranean climate type, with warm, dry summers and cool, wet winters. The winter rain is a consequence of frontal depressions developed from the circumpolar westerlies, which occur at least once per week in normal mid-winter from June to August. The summer climate is controlled by the South Atlantic High, which produces south-easterly winds, which blow offshore over the west coast. Much of the roughly 25% of the peninsula's rain that falls during the summer months of October to March is associated with post-frontal conditions.

There is a large variation in rainfall over the peninsula. Maclear's beacon at the top of Table mountain in the north has an average of 2270 mm per year, while Cape Point gets about 402 mm per year. 1

Rainfall variations are affected by altitude and aspect, and by topographical features that direct and trap rain-bearing wind. Rain from southeasterly wind clouds is substantial at higher elevations. Snowfall is unusual, restricted to Table Mountain, and melts within a day or two.

Variations in temperature are not great due to the moderating effect of the adjacent sea, the narrow land mass, and fairly low maximum altitudes of the mountains. Annual mean temperature at sea level in the north facing areas of the north peninsula are around 22 °C. and about 16 °C on the mountain top. Elsewhere, averages range between 18 and 20 °C. The range of mean maximum to mean minimum temperatures at any given place is small, ranging from 10 °C on table Mountain to 6 °C at Cape Point. Frost is unusual and not severe, even on the mountains, and is unknown at the coastline.

Winds over the peninsula can be strong. In winter, the northwesterly wind often exceeds gale force, with mean wind speeds of 20kph over the Cape Flats and 30kph at Cape Point. In summer the southeasterly and southwesterly winds may blow at gale force for over a week uninterrupted, but there are locally sheltered areas where the wind is much lighter which vary depending on wind direction.

Ecology

The peninsula is highly topographically varied, and has a wide range of annual rainfall variation over a small area, and a large diversity of nutrient poor soils, and consequently supports a wide range of habitats and ecological communities. The peninsula lies within the Cape Floristic Region of South Africa. It is the home of some 2285 plant species and is a global hot-spot of diversity for plants and invertebrates. Vegetation is dominated by about 12 types of fire-prone fynbos shrubland. Invertebrate community structure is poorly understood, and vertebrate communities are thought to be strongly influenced by recurring fire and nutrient limitations, so most vertebrates are small and population densities are low.

Table Mountain National Park, previously known as the Cape Peninsula National Park, was proclaimed on 29 May 1998, for the purpose of protecting the natural environment of the Table Mountain Chain, and in particular the rare fynbos vegetation. The park comprises a large part of the undeveloped area of the Cape Peninsula, and is managed by South African National Parks Board. The coastal waters surrounding the Cape Peninsula were proclaimed as a marine protected area in 2004, include several no-take zones, and are part of the national park. The waters of this marine protected area are unusual in that they are parts of two fairly distinct coastal marine ecoregions, namely the Agulhas ecoregion and the Benguela ecoregion. The boundary is at Cape Point.

Flora

The Cape Peninsula has an unusually rich biodiversity. Its vegetation consists predominantly of several different types of the unique and rich Cape Fynbos. The main vegetation type is endangered Peninsula Sandstone Fynbos, but critically endangered Peninsula Granite Fynbos, Peninsula Shale Renosterveld and Afromontane forest occur in smaller portions on the mountain ranges of the Peninsula. On the sandy Cape Flats lowlands there are a few pockets of protected Cape Flats Sand Fynbos.

The Peninsula's vegetation types form part of the Cape Floral Region protected areas. These protected areas are a World Heritage Site, and an estimated 2,200 species of plants are confined to Table Mountain range - which are at least as many as occur in the whole of the United Kingdom. Many of these species, including a great many types of proteas, are endemic to these mountains and can be found nowhere else. The Disa uniflora, despite its restricted range within the Western Cape, is relatively common in the perennially wet areas (waterfalls, streamlets and seeps) on Table Mountain and the Back Table, but hardly anywhere else on the Cape Peninsula. It is a very showy orchid that blooms from January to March on the Table Mountain Sandstone regions of the mountain. Although they are quite widespread on the Back Table, the best (most certain, and close-up) place to view these beautiful blooms is in the "Aqueduct" off the Smuts Track, halfway between Skeleton Gorge and Maclear's Beacon.

Remnant patches of indigenous forest persist in the wetter ravines. However, much of the indigenous forest was felled by the early European settlers for fuel for the lime kilns needed during the construction of the Castle. The exact extent of the original forests is unknown, though most of it was probably along the eastern slopes of Devil's Peak, Table Mountain and the Back Table where names such as Rondebosch, Kirstenbosch, Klaassenbosch and Witteboomen survive (in Dutch "bosch" means forest; and "boomen" means trees). Hout Bay (in Dutch "hout" means wood) was another source of timber and fuel as the name suggests. In the early 1900s commercial pine plantations were planted on these slopes all the way from the Constantiaberg to the front of Devil's Peak, and even on top of the mountains, but these have now been largely cleared allowing fynbos to flourish in the regions where the indigenous Afromontane forests have not survived, or never existed.

Fynbos is a fire adapted vegetation, and evidence suggests that in the absence of regular fires all but the drier fynbos would become dominated by trees. Regular fires have dominated fynbos for at least the past 12 000 years largely as a result of human activity. In 1495 Vasco da Gama named the South African coastline Terra de Fume because of the smoke he saw from numerous fires. This was originally probably to maintain a productive stock of edible bulbs (especially watsonians) and to facilitate hunting, and later, after the arrival of pastoralists, to provide fresh grazing after the rains. Thus the plants that make up fynbos today are those that have been subjected to a variety of fire regimes over a very long period, and their preservation now requires regular burning. The frequency of the fires obviously determines precisely which mix of plants will dominate any particular region, but intervals of 10–15 years between fires are considered to promote the proliferation of the larger Protea species, a rare local colony of which, the Aulax umbellata (Family: Proteaceae), was wiped out on the Peninsula by more frequent fires, as have been the silky-haired pincushion, Leucospermum vestitum, the red sugarbush, Protea grandiceps and Burchell's sugarbush, Protea burchellii, although a stand of a dozen or so plants has recently been "rediscovered" in the saddle between Table Mountain and Devil's Peak. Some bulbs may similarly have become extinct as a result of a too rapid sequence of fires. The fires that occur on the mountains today are still largely due to unregulated human activity. Fire frequency is therefore a matter of chance rather than conservation.

Despite intensive conservation efforts the Table Mountain range has the highest concentration of threatened species of any continental area of equivalent size in the world. The non-urban areas of the Cape Peninsula (mainly on the mountains and mountain slopes) have suffered particularly under a massive onslaught of invasive alien plants for well over a century, with perhaps the worst invader being the cluster pine, partly because it was planted in extensive commercial plantations along the eastern slopes of the mountains, north of Muizenberg. Considerable efforts have been made to control the rapid spread of these invasive alien trees. Other invasive plants include black wattle, blackwood, Port Jackson and rooikrans (All Australian members of the acacia family), as well as several Hakea species and bramble.

Floral diversity

The flora is typical of the southwestern Cape Floristic Region. The five largest families are Asteraceae (286 spp. of which 47 are in Senecio), Iridaceae (168 spp.), Fabaceae (162 spp. of which 55 are in Aspalathus), Poaceae (141 spp.), and Ericaceae (112 spp. of which 103 are in Erica). There are also 38 spp. in Oxalis (Oxalidaceae), and 37 spp. in Ficinia (Cyperaceae). The flora includes species typical of the strictly winter rainfall area of the Western Cape, but also species with a range extending into areas where more rain falls in summer.

Vegetation types

Three major plant formations are present on the peninsula: Cape Fynbos Shrublands, Renosterveld Shrublands and associated grasslands, and Forest and thicket. Fynbos has the largest coverage, historically about 92% of the area, and hosts the majority of species. It is a fire-prone sclerophyllous shrubland with a high cover of restiods. Renosterveld is also a fire-prone scrubland, but with restioids replaced by grasses, without proteoid shrubs, and with the shrub component dominated by ericoid shrubs. The third formation is Forest and thicket, which is characterised by broad-leafed, Afromontane evergreen trees and shrubs, and is not fire-prone. It grows in a variety of habitats, mostly in moist, relatively fertile soils that are protected from fire. Species diversity is relatively low.

Fynbos:

• Dune asteraceous fynbos
• Coastal scree asteraceous fynbos
• Ericaceous fynbos
• Mesic mesotrophic proteoid fynbos
• Wet mesotrophic proteoid fynbos
• Mesic oligotrophic proteoid fynbos
• Wet oligotrophic proteoid fynbos
• Sandplain proteoid fynbos
• Upland restioid fynbos
• Wet restioid fynbos
• Undifferentiated cliff communities

Other:

• Renosterveld and grassland
• Wetland
• Vleis
• Forest and thicket

Fauna

The most common mammal on the mountain was the dassie (the South African name, from Afrikaans, pronounced "dussy"), or rock hyrax. Between about 2000 and 2004 (no one is certain about the exact year or years) their numbers suddenly plummeted for unknown reasons. They used to cluster around the restaurant at the upper cable station, near areas where tourists discarded or (inadvisably supplied) food. The population crash of the dassies was in all probability responsible for the decline in the Verreaux's eagle population on the Peninsula, which is believed to have consisted of 3 breeding pairs during the period 1950 to 1990, with only 2 pairs, maximally, ever having been reported to fledge a chick each in any given year. With the commencement of formal monitoring in 1993, two breeding pairs were recorded on the Cape Peninsula Mountain Chain in 2004: one below the upper cable station at the western end of Table Mountain, in Blinkwater Ravine, the other on the cliffs below Noordhoek Peak. The nest near the cable station was abandoned in 2006, leaving only the Noordhoek pair, which continued to fledge chicks reasonably regularly till 2013, at which point one member of the pair disappeared. From 2013 till January 2017 only a single Verreaux's Eagle, presumed to be a female, remained on the Peninsula. She continued to maintain the nest under Noordhoek Peak, but seemed unable to attract a mate. But in early 2017 a pair of eagles was seen by at least 7 independent observers during the course of 10 days (27 January - 5 February). It remains to be seen whether they will breed later in the year. Dassies are an important part the Verreaux's eagle's prey on the Peninsula.

Table Mountain is also home to porcupines, mongooses, snakes, lizards, tortoises, and a rare endemic species of amphibian that is only found on Table Mountain, the Table Mountain ghost frog. The last lion in the area was shot circa 1802. Leopards persisted on the mountains until perhaps the 1920s but are now extinct locally. Two smaller, secretive, nocturnal carnivores, the rooikat (caracal) and the vaalboskat (also called the vaalkat or Southern African wildcat) were once common in the mountains and the mountain slopes. The rooikat continues to be seen on rare occasions by mountaineers but the status of the vaalboskat is uncertain. The mountain cliffs are home to several raptors species, apart from the Verreaux's eagle. They include the jackal buzzard, booted eagle (in summer), African harrier-hawk, peregrine falcon and the rock kestrel. In 2014 three pairs of African fish eagles were believed to be breeding on the Peninsula, but they nest in trees generally as far away from human habitation as is possible on the Peninsula. Their number in 2017 is unknown.

Up until the late 1990s baboons occurred on all the mountains of the Peninsula, including the Back Table immediately behind Table Mountain. Since then they have abandoned Table Mountain and the Back Table, and only occur on the Constantiaberg, and the mountains to the south. They have also abandoned the tops of many of the mountains, in favour of the lower slopes, particularly when these were covered in pine plantations which seemed to provide them with more, or higher quality food than the fynbos on the mountain tops. However these new haunts are also within easy reach of Cape Town's suburbs, which brings them into conflict with humans and dogs, and the risk of traffic accidents. In 2014 there were a dozen troops on the Peninsula, varying in size from 7 to over 100 individuals, scattered on the mountains from the Constantiaberg to Cape Point. The baboon troops are the subject of intense research into their movements (both of individuals and of the troops), their physiology, genetics, social interactions and habits. In addition, their sleeping sites are noted each evening, so that monitors armed with paint ball guns can stay with the troop all day, to ward them off from wandering into the suburbs. From when this initiative was started in 2009 the number of baboons on the Peninsula has increased from 350 to 450, and the number of baboons killed or injured by residents has decreased.

Himalayan tahrs, fugitive descendants of tahrs that escaped from Groote Schuur Zoo near the University of Cape Town, in 1936, used to be common on the less accessible upper parts of the mountain. As an exotic species, they were almost eradicated through a culling programme initiated by the South African National Parks to make way for the reintroduction of indigenous klipspringers. Until recently there were also small numbers of fallow deer of European origin and sambar deer from southeast Asia. These were mainly in the Rhodes Memorial area but during the 1960s they could be found as far afield as Signal Hill. These animals may still be seen occasionally despite efforts to eliminate or relocate them.

On the lower slopes of Devil's Peak, above Groote Schuur Hospital, an animal camp bequeathed to the City of Cape Town by Cecil John Rhodes has been used in recent years as part of the Quagga Project. The quaggas used to roam the Cape Peninsula, the Karoo and the Free State in large numbers, but were hunted to extinction during the early 1800s. The last quagga died in an Amsterdam zoo in 1883. In 1987 a project was launched by Reinhold Rau to back-breed the quagga, after it had been established, using mitochondrial DNA obtained from museum specimens, that the quagga was closely related to the plains zebra, and on 20 January 2005 a foal considered to be the first quagga-like individual because of a visible reduced striping was born. These quagga-like zebras are officially known as Rau quaggas, as no one can be certain that they are anything more than quagga look-alikes. The animal camp above Groote Schuur Hospital has several good looking Rau quaggas, but they are unfortunately not easily seen except from within the game camp, which is quite large and undulating, and the animals are few. The animal camp is not open to the public.

Human impact

The nutritionally impoverished soils of the Cape Peninsula limited pre-colonial animal numbers, and thereby also the density of human settlement it could support, but there has been hunter-gatherer human occupation going back more than 200,000 years, The early San occupants used 'firestick farming' to manage the natural vegetation for game and geophytes. These long term practices are thought to have influenced the development of fynbos in areas where thickets would likely be the dominant vegetation community, and encouraged greater floral biodiversity. About 2000 years ago the San were displaced by Khoikhoi who were mainly nomadic pastoralists who kept fairly large numbers of sheep and cattle at lowland sites in the central and northern peninsula during the dry season.

Colonisation by the Dutch had an immediate transformative effect on the lower altitude ecosystems of the northern peninsula when agriculture was introduced, and rapidly expanded between Table Bay and Wynberg. The forests of the lower slopes and flats of the eastern side of Table Mountain and the Hout Bay valley were soon depleted. Alien replacements, largely oaks and pines, were introduced from Holland to replace the natural forests, since about 1655. Dutch expansion into the south peninsula was slow, partly due to difficult access, but was encouraged by the use of Simon's Bay as a winter anchorage from 1743, as Table Bay is exposed to the north-westerly storms, which drove many ships aground. Farms in this area granted to 'free burghers' were largely used for hunting and limited market gardening. The expanding colony and a smallpox epidemic led to the social and economic collapse of the Khoikhoi by 1713.

Liberalisation of trade following the second British capture of the Cape Colony in 1806 led to rapid growth of the population of the peninsula. By this time the population of the greater Cape Town area reached about 22,000 settlers, 25,000 slaves and remaining Khoikhoi. The arrival of the 1820 Settlers increased the population of European descent to about 47,000. The British made Simon's Town an official naval base, and this encouraged the growth of transport and other infrastructure in the area. Simon's Town flourished during the Anglo-Boer wars, and the two world wars, but agriculture in the peninsula remained limited by terrain and soils. Most of the produce supplied to the visiting ships came from the Cape Flats and beyond.

Extensive plantations of fast growing alien trees were established during the mid to late 19th century on the slopes of the central Peninsula and Table Mountain (mostly pines and eucalypts), and on the sands of the Cape Flats (mostly Australian acacias). These lead to alien plant invasions which threaten the remaining natural ecosystems of the peninsula. Urban areas also expanded along the eastern slopes of Table Mountain, and later along the smaller wastern slopes, into the Cape Flats, and along the east coast of the south peninsula from Muizenberg to Simon's Town.

Cape Town grew rapidly during the 20th century: By the 1960s the population reached half a million, In the late 1980s discriminatory legislation was relaxed and a large influx of rural people moved in and started informal settlements on open ground. By 1994 it had increased to 2.2 million, and by 2020 it was over 4 million. This rapid growth increased pressures on the natural ecosystems, particularly where land supporting natural ecosystems was occupied.

In 1996 about 37% of the region was in use for agriculture and urbanization and 44% of the remaining area of natural vegetation had been invaded by alien plants. However, about 64% of the peninsula was within the Cape Peninsula Protected Natural Environment which includes three major nature reserves, and which was later proclaimed as the Table Mountain National Park.