Lower Tokai Park originally comprised a heathland vegetation type (as part of the once continuous Fynbos BIOME), which included species of Erica and other tiny, hard-leaved shrub species amongst many others. This is the only biome defined by soil nutrient status alone – as opposed to other biomes which are defined by climate. SANParks aims to restore the Lower Tokai area, previously under pines for approximately 130 years, and return it to its previous state. The intent is admirable, but it is, unfortunately, ecologically impossible.
The world has moved on from 130 years ago. Today we are faced with climate change and urban densification, both of which impact negatively upon the original heathlands.
The encroachment of the urban edge has meant that garden fertilizers and compost mixtures have filtered into the soils surrounding Lower Tokai. Generations of horse riders, dog walkers and ramblers have further added to the natural fertilization process. Road and gravel path building have impacted. And most obviously, over 100 years of pines have produced their own organic composting through pine needles, cones, bark and branches. Add into that mix the prevalence of nitrates and phosphates borne aerially from the city’s atmosphere, and what was once a nutrient poor soil has become increasingly nutrient enriched.
This is not something that can be undone, the soil has changed and with it the vegetation. Anyone walking through the fynbos section of Lower Tokai will be aware of vast tracts of Mediterranean grasses – the natural spinoff of soil that has seen – and continues to see – nutritional improvement. What was once a heathland is increasingly becoming grassland.
For those who wonder about the current presence of proteas, ericas and restios – a significant amount of planting of these species has been done in conjunction with the South African National Botanical Institute (SANBI – Kirstenbosch), and at tremendous cost, in an attempt to regenerate the past. The reality is that seed beds are mostly extinct, the soil has changed, and a specific species of ant required to disseminate seed has been replaced by an Argentinian ant. The entire regeneration effort, one might say, is not unlike “trying to bring back the dodo”.
For more information read Botany 101 – Understanding the ecological drivers of Cape Flats Sandplain Fynbos of Lower Tokai by Professor Eugene Moll