Biological diversity in the Cape Floristic Region
Hugging the coastline along the far southwestern tip of the African continent, the 78,555 km2: Cape Floristic Region hotspot is located entirely within the borders of South Africa. It is one of the five temperate Mediterranean-type systems on the Conservation International hotspots list, and is one of only two hotspots that encompass an entire floral kingdom (the other being New Caledonia).
The vegetation on the Cape is dominated by fynbos (an Afrikaans word for “fine bush”), a shrubland comprising hard-leafed, evergreen, and fire-prone shrubs that thrives on the region's rocky or sandy nutrient-poor soils. Although the region was once covered by lush rain forest, climate changes around 15 million years ago resulted in the retreat of the forests. Trees were replaced by flammable sclerophyllous plants, and periodic fires became an integral ecosystem process.
The Cape also includes several non-fynbos vegetation types. Of these, Renosterveld (Afrikaans for “rhinoceros veld,” referring to the presence of the black rhinoceros (Diceros bicornis), that used to browse there but is now extinct in this region) is the most extensive, covering some 20 000 km2. This plant community comprises a low shrub layer, usually dominated by the renosterbos (Elytropappus rhinocerotis), with a ground layer of grasses and seasonally active bulbs.
Today, trees are very rare in pristine Cape landscapes and true forests occupy a mere 3,850 km2, mostly in moist, fire-protected sites on the southern coastal forelands and lower mountain slopes. The Cape forests, 10-30 meters tall, are essentially outliers of the Afromontane forests of the high mountains of tropical Africa.
Unique and Threatened Biodiversity
The Cape Floristic Region is home to the greatest non-tropical concentration of higher plant species in the world, with 9,000 species crammed into its small extent. Incredibly, more than 6,200 (69 percent) of these species are found nowhere else in the world. Furthermore, five of South Africa's 12 endemic plant families and 160 endemic genera are found only in this hotspot.
Certain genera have undergone massive diversification—the 10 largest genera account for 21.5 percent of the flora—with the two most speciose being Erica (Ericaceae: 658 species) and Aspalathus (Fabaceae: 257 species). Species richness and local endemism is greatest in the southwest; the Cape Peninsula (471 km2) alone supports 2,256 species (including 90 endemics).
Among the best-recognized plant species in the hotspot are the proteas, particularly the king protea (Protea cynaroides), which is South Africa's national flower, and the red disa (Disa uniflora). Also worth a mention is the Clanwilliam cedar (Widdringtonia cedarbergensis, EN), a graceful but declining relict conifer endemic to the Cederberg mountains in the northwestern part of the region.
The avifauna of the Cape Floristic Region is characterized by low diversity, most likely the result of structural uniformity in the vegetation and a shortage of available food. Of the 320 or so regularly occurring species of land birds here, only six are endemic. Nevertheless, the area is considered an Endemic Bird Area by BirdLife International, and is home to a number of true fynbos species such as the Cape sugarbird (Promerops cafer), the orange-breasted sunbird (Nectarinia violacea), the Protea canary (Serinus leucopterus) and the Cape siskin (Serinus totta). Although the more widespread Cape griffon (Gyps coprotheres, VU) can still be found in the hotspot, happily none of the endemic birds are considered threatened.
While the Cape region never supported concentrations of animals as dense as the African savannas, it did once have significant populations of many of the well-known large mammals, including common eland (Tragelaphus oryx), African buffalo (Syncerus caffer), lions (Panthera leo, VU), black rhinoceros, African elephant (Loxodonta Africana, VU), Mountain zebra (Equus zebra, EN), and hippopotamus (Hippopotamus amphibius). Today, however, nearly all of these populations have disappeared or have been reduced to tiny remnant groups. Two of the most interesting mammals that once lived on the Cape are now extinct: the bluebuck (Hippotragus leucophaeus) and the quagga (Equus quagga), a subspecies of the plains zebra that had no stripes on the rear part of its body, both disappeared in the 1800s.
Today, there are about 90 species of mammals in the hotspot, four of which are endemic, including two species of golden moles: the Fynbos golden mole (Amblysomus corriae) and Van Zyl’s golden mole (Cryptochloris zyli, CR). Of the region's remaining large mammals, one of the most beautiful is the bontebok (Damaliscus dorcas dorcas), an antelope that, though nearly extinct in the mid-1800s, was saved by the dedication of a small group of conservationists. Today, the bontebok numbers about 2,000, and the prospects for the species’ survival are quite good. The hotspot is also the home of several small solitary antelope species including the Cape grysbok (Raphicerus melanotis).
Reptile diversity in the Cape Floristic Region is relatively high, with about 100 species, nearly a quarter of which are endemic. The Cape boasts an impressive level of tortoise diversity. South Africa itself has the highest tortoise diversity on Earth, and five species are found almost exclusively within the Cape Floristic Region. These include the angulate tortoise (Chersina angulata); parrot-beaked tortoise (Homopus areolatus); geometric tortoise (Psammobates geometricus, EN); and leopard tortoise (Geochelone pardalis). The geometric tortoise is one of the rarest tortoise species in world. It has lost 97 percent of its habitat, and only 2,000-3,000 individuals survive in approximately 30 localities in a small patch of about 50 km2.
There are more than 40 species of amphibians in the hotspot. Sixteen of these are endemic, including the Table Mountain ghost frog (Heleophryne rosei, CR) which is found only on the slopes of Table Mountain between 240 and 1,060 meters above sea level. Two amphibian genera are endemic, each represented by a single species: the micro frog (Microbatrachella capensis, CR), found in sandy, coastal fynbos heathland, and the montane marsh frog (Poyntonia paludicola), a species of mountain fynbos heathland.
Of the nearly 35 native freshwater fish species in the Cape Floristic Region, more than a dozen are endemic. Some of the more distinctive fishes in the clear mountain streams of this region include the Cape galaxias (Galaxias zebratus), an elongated, scaleless fish, as well as several species of endemic redfin minnows (Pseudobarbus spp.).
Although little is known about the invertebrate fauna of the region, the few groups that have been studied suggest high levels of endemism. Of more than 230 species of butterflies, about 30 percent are endemic. One study on the Cape Peninsula found 111 invertebrate endemics in 471 km2, a level higher than that of plants.
Today, a range of human activity seriously threatens the unique vegetation of the Cape Floristic Region. Agricultural expansion has reduced lowland habitats such as the Sandplain fynbos and Coast renosterveld by 83 percent and 48 percent of their original extent, respectively. Much of what remains exists in isolated fragments in a matrix of chemically treated agriculture. Agricultural development is encroaching on natural areas even in the mountains, where impoverished soils previously limited agriculture; farming of rooibos tea, (Aspalathus linearis), honeybush tea (Cyclopia spp.), cut flowers (mainly Proteaceae), and, of course, vineyards pose a significant threat to the remaining vegetation.
In addition, urban encroachment and development, particularly near the city of Cape Town, is a threat to natural habitats.Although urban and industrial areas currently occupy less than 1 percent of the land area in the hotspot, population is growing rapidly; Cape Town's population is expected to double by the year 2025.
However, the greatest threat to this hotspot is the effect of invasive alien plant species. For decades, trees and shrubs from other Mediterranean-type climates such as southern Australia, the Mediterranean Basin, and California have been introduced into the region to supplement the few tree species native to the Cape. These alien species have invaded about 70 percent of mountain and lowland fynbos, altering natural fire frequencies, diminishing mountain-derived water production, and ultimately eliminating native species.
Overall, some 33 percent of the Cape Floristic Region has been transformed by agriculture, urbanization and dense stands of alien invasive plants. However, only about 15,700 km2, or 20 percent, is in pristine condition, being free of invasive alien plants and subject to appropriate fire regimes.
Conservation Action and Protected Areas
According to the World Database on Protected Areas, about 10,859 km2, representing about 14 percent of the total land area, in the Cape Floristic Region is in protected areas, nearly all of it in IUCN categories I to IV. However, this land is far from representative of the hotspot's full diversity; while 50 percent of the mountain landscapes are conserved, only nine percent of the lowlands, which are the most vulnerable, are under some form of protection.
Although the high costs of land purchase and park management activities have posed serious challenges to conservation in the region, a number of recent successes point to a more optimistic future for the hotspot's biodiversity. These achievements have helped to strengthen the already tremendous level of public awareness about the value of the province and its fauna and flora.
Among many promising projects is an initiative called the Working for Water Programme, which focuses on the removal of alien plants to encourage the regeneration of native vegetation and protection of watersheds. The program has created 3,600 jobs in the region and led to the clearing of nearly 500 km2 of alien growth, one of the most impressive efforts of its kind in the world.
There have also been a number of triumphs in the establishment of new protected areas, including the Cape Peninsula National Park, the Cape Agulhas National Park, and the West Coast Biosphere Reserve. At a recent meeting in Suzhou, China, UNESCO recognized the importance of this region by declaring it a World Heritage Site for its "outstanding universal significance to humanity." Eight protected areas together comprise the Cape Floristic Region World Heritage Site, one of which includes Kirstenbosch National Botanical Garden, the first time that a botanical garden has been recognized as a world heritage site for its biodiversity. The areas included in the world heritage site are Table Mountain, Baviaanskloof, De Hoop Nature Reserve, Boland Mountain Complex, Groot Winterhoek Wilderness Area, Swartberg Complex, Boosmansbos Wilderness Area, and Cederberg Wilderness Area. These eight separate protected areas total more than 553,000 hectares, making this World Heritage Site the richest for plants in the world on a per area basis.
It is hoped that UNESCO listing will help to encourage the 'biodiversity economy' in the region, and will promote eco-tourism and better planning and management of the region's incredibly rich natural resources, protected areas, and scenic landscapes for the benefit of all South Africans. Already, the Cape Action Plan for the Environment, a $6 million project funded by the GEF and World Bank, is supporting the development and implementation of a strategic plan for sustainable conservation of the hotspot's unique flora and fauna, and a $6 million investment by the Critical Ecosystem Partnership Fund is being used partially to support three mega-reserves: Baviaanskloof, Cederberg and Gouritz, and to build the capacity of previously disadvantaged local conservationists.
- This article is based on contributions from Richard M. Cowling and Shirley M. Pierce.
- For a complete list of all contributors to the Biodiversity Hotspot program, see Biodiversity Hotspot Site Credits.
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