The flora of the Addo Elephant National Park, South Africa: are threatened species vulnerable to elephant damage?

Abstract

The Addo Elephant National Park in the warm-temperate Eastern Cape was proclaimed in 1931 to protect one of the four elephant populations in South Africa which survived into the present century. However, since the late 1970s, a major objective of the Park is to protect intact a viable example of succulent thicket – the regional ecosystem. Succulent thicket is endemic to the Eastern Cape and forms the major component of the Albany Centre, a floristic region of high diversity and endemism, especially among succulent shrubs and geophytes. This ecosystem is poorly represented in the reserve system and is highly threatened by overgrazing and clearing for agriculture. Under the present stocking rate of more than two elephants/km2, succulent thicket in the Park has been severely impacted: in particular, biomass, stature and plant diversity have been reduced. We show that the flora of the Park is of great regional significance. Of a total of 581 species, 12.4% were classified as regional endemics and/or Red Data Book species (collectively termed 'species’ of special concern), and 32.2% were not known to be conserved in any other succulent thicket protected area. Relative to the remainder of the flora, both categories of species were over-represented among succulent shrubs (predominantly Euphorbiaceae and Mesembryanthemaceae) and geophytes (predominantly Asphodelaceae and Hyacinthaceae). This taxonomic and biological profile coincides with that of species vulnerable to local extinction as a result of elephant impacts. The Park authorities will need to find a solution to the conflict between maintaining a large population of megaherbivores, and maintaining the structure and diversity of succulent thicket.