Chapmans Peak Nature Sanctuary
The World’s Richest Coastal Dune Flora
Dr Donovan Kirkwood (Curator, Stellenbosch University Botanical Garden)
Dr Rob Anderson (chairman, NEAG)
Prof Richard Cowling (Nelson Mandela University)
(Photos D Kirkwood and R Anderson)
Few of us who stroll through the dunes behind Noordhoek Beach realise that our coastal flora is up to three times richer in species than anywhere else in the world with a similar winter rainfall (Mediterranean) climate.
Globally, the floras on coastal sands are distinct from inland floras because the soil is always alkaline due to the calcium carbonate of shells, and the plants are subjected to strong, salty winds. Also, because sea levels have changed in the recent geological past, these species are also all relatively recent, most having evolved in the past one to three million years. During the ice ages, lower sea levels exposed bigger coastal plains, providing a far greater area in which different species could evolve. Even though the sea level has risen considerably since the last glacial maximum 15,000 years ago, we are still left with this high floral diversity.
Conditions on Mediterranean-climate dunes are particularly harsh because the very dry summers limit the number of species that can survive. But unusually, the Cape had such a richly diverse fynbos flora from which the coastal flora could evolve. What also increases our floral diversity is that our species could evolve from tropical, subtropical as well as the older and incredibly rich temperate fynbos floras.
Noordhoek has several areas of outstanding dune and Strandveld vegetation. The Chapman’s Peak Sanctuary (below the Red Herring) covers only 3.7 hectares (ha), of which roughly half is endangered Cape Flats Dune Strandveld, and the other half is Southern Coastal Forest (milkwood forest). The more extensive dunes behind Noordhoek Beach, being closer to the sea, contain fewer species than the Sanctuary, which lies further from the sea, but have a few very hardy and salt-tolerant species of their own.
While dune floras from similar-sized areas of other Mediterranean regions would at most contain 40-50 species, our dunes are home to well over a hundred. NEAG surveys here have already identified approximately 110 indigenous species, and that doesn’t even include most of the native grasses and many small annuals and herbaceous plants. There are certainly many more plants still to be identified.
Sadly, our rich Cape dune flora is highly endangered, because we have left only a small fraction of what used to exist. Development has covered most of the sandy areas in the Western Cape, especially the richest habitats just behind the beach dunes. Many habitat remnants are under threat. The Cape flats, once a vast swathe of Strandveld, was deliberately stabilised by the planting of alien trees, and is now almost covered by human settlement, roads or farms. The first land to be developed in coastal towns was invariably the flat, sandy lowlands – the Strandveld.
Our Strandveld is irreplaceable. In Noordhoek the back-beach dunes are reasonably safe from development, because they (mostly) fall within a SANParks protected area. The Chapmans Peak Sanctuary, with its even richer flora, is especially in need of long-term protection. So next time you feel like a stroll, have a careful look at the flora, and enjoy the privilege of walking in the richest Mediterranean-climate, dune flora in the world!