Cape Floristic Region Biodiversity

Cape Floristic Region Biodiversity



Cape Floristic Region Biodiversity

Introduction

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 (Bond, P. & Goldblatt, P. 1984).

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 (Van et al, 1996).

Biodiversity issues

Plants

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 (Vlok et al, 2003).

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 (Skelton, 1993).

Vertebrates

Birds

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 (Branch, ...