More than just Grass! The amazing biodiversity of the Woodbush Granite Grasslands derives mainly from its wildfowers, veld flowers in South African parlance. Isolated trees do occur, such as Acacia spp. especially A. sieberiana, the Common Spike-Thorn Gymnosporia buxifolia and Cabbage Trees (Cussonia spp.). Several indigenous forest patches also dot the grasslands, but it is the wildflowers which steal the show.
According to taxonomist Pieter Winter, around 630 plant species have been recorded from the Haenertsburg Grasslands, an area of roughly 240 ha. Winter's Analysis of the Flora of the Haenertsburg Commonage (Haenertsburg Townlands) is the key reference for the botanical aspects of these grasslands.
Of the roughly 630 plants species, only 53 grasses have been recorded. The bulk of the biodiversity is made up of forbs; or wildflowers. The family Asteraceae is well represented, with 94 species. The most common genus is Helichrysum (Everlastings) with 21 species, while orchids, Gladioli, Watsonias, Aloes and many more are also found.
A special place is just below the Haenertsburg Primary School, between the school and the Roads Camp. A series of rocky outcrops here harbours many Blue Squills (Merwilla plumbea) as well as Aloes and the Bushman Poison Bulb, Boophone disticha. Blue Squills prefer rocky places but are also found in sandy soil on the Ebenezer Dam Peninsula, which is also a protected area.
Many of these grassland plants are used medicinally, which is part of the reason that these grasslands are of economic value. A number of traditional healers collect plants from the grassland, and are in contact with FROHG so that we gain some idea of the species and numbers harvested.
Why is the Grassland so rich in species?
One answer is that this area was never glaciated (unlike much of the northern hemisphere). These grasslands have been dated back to about 18 000 years ago, using various technologies such as fossil pollen studies. If an ecosystem is around that long in a relatively undisturbed state, it has a chance to evolve many unique species which are found nowehere else. By contrast, if an ecosystem experiences repeated glaciation events, the whole ecosystem has to start from scratch every time and a comparatively species-poor ecosystem results. The Great Lakes region of the USA is an example of this. South Africa has far more plant species than the entire USA, which is a much larger area.
The Louis Changuion Hiking Trail meanders through four or five forest patches, which are home to large trees such as Yellowwoods, Cabbage Trees, White Stinkwoods, Cape Chestnuts and Fig Trees. Lianas (vines) span the canopy, which is home to many birds including the Knysna Lourie. Vervet monkeys, duikers and bushbuck also inhabit the forests.
Blue Swallows and Methuens Dwarf Gecko are just two red data species recorded from these grasslands and vicinity. Eastwoods Long-tailed Seps, a snake-like lizard not seen for 80-odd years, is believed by some scientists to still live here. The Wolkberg Zulu butterfly, a critically endangered insect recorded only from a tiny grassland patch near Haenertsburg, is another species reliant on these grasslands. The Bolas Spider, which hunts moths, gaucho-style, with a silk thread, was found here a few years ago. It was previously known only from KZN. Secretary birds were seen in the Haenertsburg grasslands during 2007, for the first time in many years. Unfortunately one flew into a powerline and died.
Irreplaceability Map hilighting the relative importance of the Haenertsburg Grasslands - Mucina & Rutherford 2006
Global change includes the effects of increased atmospheric carbon dioxide levels and the associated changes in temperature and rainfall. In the immediate future (2050) of eastern South African these predicted changes include an increase of 2-3oC and a more variable rainfall regime with more intense wet periods interrupted by prolonged periods of drought. These changes are likely to impact ecosystems at higher altitude first, such as those on the slopes of the northern escarpment in Limpopo. The interaction between climate and fire frequency currently determines the distribution of the grassland, savanna and forest biomes in the region. Global change has the potential to alter the composition and distribution of these vegetation types. A common prediction is for the encroachment of savanna and forest tree species into the threatened remains of open grasslands. However, no on-the-ground research has been carried out to test this prediction and this limits our ability to plan for their protection in the future.
Published in 2009, out of print.