Botany 101: Understanding the plant ecological drivers of the Cape Flats Sand Fynbos of Tokai

by Professor Eugene Moll

Capetonians sit in the middle of what botanists call the “GREATER CAPE FLORISTIC REGION” (GCFR) the heart of which was once was loosely referred to as the… “CAPE FLORISTIC KINGDOM”.

This tiny space, one of only six global “Floral Kingdoms”, is renowned for its floristic diversity and unique vegetation that many refer to locally as “FYNBOS”…

Floral Kingdoms of the World

Where and what is the “Cape Floristic Kingdom”?

Cape Floristic Kingdom
• Number of vascular plant species about 9,000
• Size ~90,000 km2
• 68.7% species are endemic (i.e. occurring nowhere else in the whole world)…

This is comparable only to the Wet Tropics

Within the GCFR, a number of major vegetation types (or BIOMES) occur. Mostly they are determined by climate (basically the winter rainfall zone of southern Africa), WHILE one vegetation type by soil nutrient status alone.

South Africans have been slow in understanding that one of their biomes is in fact a HEATHLAND*.
*The only global vegetation type not climatically determined (Specht et al. 1981)

Heathlands are a global vegetation type, mostly restricted to the southern hemisphere (and substantial in Australia), whose distribution is NOT determined by climate but by low soil nutrient status. South African botanists, ecologists and environmentalists have taken a long time to realise this, and many still do not. Nor do they realise the implications of constantly adding minute amounts of nutrients to a heathland… It slowly becomes a grassland (Specht et al. 1958).

The special case of Tokai Park (also known as Lower Tokai Forest)

The vegetation here is Cape Flats Sand Fynbos (CFSF) that is listed as CRITICALLY ENDANGERED – mostly because of habitat loss. Of the 19% remaining, <1% is conserved, way less than the 30% national target.

Hence SANParks’ aim to restore the Tokai Park area, previously under pines since the first plantations were planted in 1885, and return it to its previous state – is a most noble objective.

HOWEVER, this is ecologically impossible because of five key constraints and conditions:

Heathlands, and CFSF is just one of many Heathland types in the GCFR, is a fire driven ecosystem. And for proper management, the fires need to be under extreme conditions (see the recent work of Bond et al.). Such extreme management fires in an urban context are simply impossible.
The Tokai Park fragment, and any tiny adjoining fragments, are now isolated islands and thus there can be no gene flow between it and any other remaining areas. Such genetic isolation leads to genetic loss over time: i.e. Cape Flats Sand Fynbos species will decline.
Already enormous energy has gone into the manual replanting a number of species in Tokai Park (in conjunction with SANBI – Kirstenbosch) because all the species that would have been present ~100 years ago are no longer in the seed-bank (in fact just a very few are). Such expensive restoration is not sustainable with current budgets.
Another management issue are the alien plants that are spread throughout the area. Because of the urban setting re-invasion will continue to be a nightmare into the future.
BUT the real problem for restoration of Cape Flats Sand Fynbos (CFSF) is…
Nutrient input. Since CFSF is a Heathland, and Heathlands are determined by low soil nutrient status, the Tokai Park area is a place where there are already additional nutrient loads and these will only increase over time. So where do these additional nutrients come from that will “poison” the fynbos species the historically grew here? There are many sources but I will only focus on two:
1. One key source is that because Tokai Park is in an urban setting there are, and will continue to be, aerial inputs from the city atmosphere – which is rich in phosphates & nitrates
  +++ which are key elements driving Heathlands (remember they thrive in low nutrient environments)Most Heathlands can only tolerate ~1 ppm P and ~100 ppm N. Anything more allows grasses to invade (see Rondebosch Common as a prime example & Specht et al. 1958).
2. Another key source of nutrient input is from humans and their activities – from people themselves (skin cells, perspiration, stuff off foot-wear, excretions and pathway hardening material) and from their animals (dogs and horses).